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Hello there, and welcome to Life Beyond Scene, where the deepest questions are often the quietest ones, waiting at the bottom of something too dark to see into, too far to easily reach, and too vast to fully understand.
A deep dive into the Diamantina Deep, an 8,047 m trench in the Eastern Indian Ocean named after HMAS Diamantina, and why it remains almost unexplored.
Key Takeaways
- The Diamantina Deep is one of the deepest known points on Earth yet remains almost entirely unexplored biologically.
- Its origin as a transform fault system makes it geologically distinct from typical subduction trenches.
- Its unique ocean environment suggests it may host unique species and adaptations.
- Targeted expeditions using modern landers and eDNA could reveal much about hadal life there.
What the video covers
- The Diamantina Deep is a roughly 8,047 m deep point in the Eastern Indian Ocean, about 1,100 km southwest of Perth, Australia.
- It lies within the Diamantina Fracture Zone, a roughly 2,500 km long transform fault system formed by lateral shearing of tectonic plates rather than subduction.
- The deep was first recorded in 1960 by HMAS Diamantina, an Australian frigate converted for oceanographic survey work, using echo sounding.
- Despite being known for over 60 years, the Diamantina Deep has received almost no dedicated biological exploration and no crewed or lander-based sampling.
- Its water chemistry, circulation, sediment characteristics and geological history differ from better-studied trenches like the Mariana, Kermadec and Atacama.
- Organisms there would likely include amphipods and polychaete worms, possibly distinct from those in other trenches.
- The video notes that many hadal species are described only decades after discovery, suggesting the deep may hold undocumented life.
- A proposed expedition would use free-fall landers with cameras, bait and sampling gear, environmental DNA analysis, and sediment cores over roughly 10-14 days on site.
- The narrator frames the deep as a reminder of how little of the ocean's deepest parts humans have actually observed.
Full Transcript — Download SRT & Markdown
Speaker A
Tonight, we're going somewhere that most maps show as nothing more than a thin blue shadow in the Eastern Indian Ocean.
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Tonight, we're going somewhere that most maps show as nothing more than a thin blue shadow in the Eastern Indian Ocean.
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up at from that part of the world. It is one of the deepest points on the surface of this planet. and in a very real sense. Almost no one has ever looked at it. Before we go any further, I want to
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A place with a name that sounds almost elegant, almost musical when you say it slowly. The Diamantina Deep. 8,047 m of cold, pressurized darkness, sitting beneath an ocean that itself sits beneath a sky most of us will never look up at from that part of the world.
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where the world has gone a little still and your mind is ready to wander somewhere far.
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It is one of the deepest points on the surface of this planet, and in a very real sense, almost no one has ever looked at it.
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would love it if you took a moment to like this video and subscribe to the channel. It genuinely helps more people find their way here, and it means we can keep making things like this together.
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Before we go any further, I want to ask you something simple. Where are you right now? What time is it where you are? Are you in bed with the lights already off, or sitting somewhere quiet with something warm in your hands? Maybe it is late. Maybe it is the kind of hour where the world has gone a little still and your mind is ready to wander somewhere far.
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incomprehensible stretch of time. The Diamantina Deep is one of those places. It did not form because of a dramatic collision or a sudden catastrophe. It formed because tectonic plates drifted millimeter by millimeter across millions of years, and the
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Whatever the answer is, I am glad you are here. This is one of those stories that deserves to be told slowly, in the dark, when there is no rush to get anywhere. If this kind of quiet exploration is something you enjoy, I would love it if you took a moment to like this video and subscribe to the channel. It genuinely helps more people find their way here, and it means we can keep making things like this together.
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that. Geographically, the Diamantina Deep sits in the Eastern Indian Ocean, roughly 1100 km southwest of Perth, Australia.
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Now, let us go somewhere very far away. There is a particular kind of place in the natural world that exists not because anyone designed it or chose it, but simply because the planet moved and kept moving over an almost incomprehensible stretch of time. The Diamantina Deep is one of those places. It did not form because of a dramatic collision or a sudden catastrophe. It formed because tectonic plates drifted millimeter by millimeter across millions of years, and the seafloor pulled apart and dropped in some places while rising in others, until eventually a long, narrow depression existed in the crust of the Earth, sitting quietly beneath roughly 4,000 m of open ocean water and then dropping further still into the darkness below that.
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is part of the Diamantina fracture zone, a much larger geological feature that stretches roughly 2 and a half thousand km from east to west across the seafloor. The fracture zone is not simple trench. It is not the kind of
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Geographically, the Diamantina Deep sits in the Eastern Indian Ocean, roughly 1,100 km southwest of Perth, Australia.
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complex to map and even harder to navigate with deep sea equipment. Within that fracture zone, there is a section where the seafloor drops to approximately 8,047 m. That is the Dear Mantina Deep. That number places it among the deepest
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That's a long way from shore. Not impossibly far for a research vessel, but far enough that getting there takes days, and staying there long enough to do serious science requires real commitment, real resources, and a specific reason to go. The deep itself is part of the Diamantina Fracture Zone, a much larger geological feature that stretches roughly 2,500 km from east to west across the seafloor. The fracture zone is not a simple trench. It is not the kind of clean, steep-sided slot that you might picture when you think of the Mariana Trench. It is more like a long, irregular rift, a landscape of parallel ridges and valleys, with walls rising and falling thousands of meters over relatively short horizontal distances, making it complex to map and even harder to navigate with deep-sea equipment.
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the surface of the water, the scale of it is genuinely hard to hold in the mind. The name itself comes from a ship.
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Within that fracture zone, there is a section where the seafloor drops to approximately 8,047 m. That is the Diamantina Deep. That number places it among the deepest points in the entire Indian Ocean and among the deepest known locations in any ocean on Earth. For context, if you placed Mount Everest at the bottom of the Diamantina Deep, the summit would still be more than a kilometer beneath the surface of the water. The scale of it is genuinely hard to hold in the mind.
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technology, which works by sending a pulse of sound downward through the water and measuring how long it takes for the echo to return from the seafloor.
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The name itself comes from a ship. HMAS Diamantina was an Australian River-class frigate, a vessel that had served during the Second World War and was later converted for oceanographic survey work. In 1960, the Diamantina was conducting depth soundings in the eastern Indian Ocean using echo sounder technology, which works by sending a pulse of sound downward through the water and measuring how long it takes for the echo to return from the seafloor.
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it. That is a tradition in oceanography, and it is a fitting one. Hm. A S Diamantina did something genuinely important that day, even if the world did not pay much attention. Subsequent surveys by Australian and international vessels refined the baometric picture of
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During those surveys, the ship recorded a depth reading near the coordinates of approximately 35° south, 105° east, a number deep enough to mark the location as one of the most significant bathymetric discoveries in the Indian Ocean. The deep was named after the ship that found it. That is a tradition in oceanography, and it is a fitting one. HMAS Diamantina did something genuinely important that day, even if the world did not pay much attention.
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more you sit with it. Despite being one of the deepest places on the planet, despite being known to science since 1960, the Diamantina Deep has received almost no dedicated biological exploration. No crude submersible has ever descended to its floor. No Hadal
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Subsequent surveys by Australian and international vessels refined the bathymetric picture of the region over the following decades. The maps got more detailed. The shape of the fracture zone became clearer. But refining a map is not the same as exploring a place.
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years, but we know almost nothing else. Compare that just for a moment to the Challenger Deep in the Mariana Trench.
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And here is the part that becomes quietly astonishing the more you sit with it. Despite being one of the deepest places on the planet, despite being known to science since 1960, the Diamantina Deep has received almost no dedicated biological exploration. No crewed submersible has ever descended to its floor. No hadal lander, as far as the scientific record shows, has been deployed to the deeper sections of the fracture zone specifically to collect biological samples from the 8,000 m zone. We know the number. We have known it for over 60 years, but we know almost nothing else.
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the DSV limiting factor. During the five deeps expedition in 2019, it has been mapped in extraordinary detail. It has been sampled biologically. It has been studied, filmed, and documented from multiple angles. The Diamantina Deep in the same 60 plus years has essentially
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Compare that, just for a moment, to the Challenger Deep in the Mariana Trench. Since Don Walsh and Jack Piccard reached the bottom in 1960, the same year HMAS Diamantina made its discovery, the Challenger Deep has been visited by crewed submersibles more than a dozen times, including James Cameron's solo descent in 2012 and multiple dives by the DSV Limiting Factor. During the Five Deeps Expedition in 2019, it was mapped in extraordinary detail. It has been sampled biologically. It has been studied, filmed, and documented from multiple angles. The Diamantina Deep, in the same 60-plus years, has essentially been left alone.
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When researchers assessed which parts of the deep ocean were least known, the Diamantina region came up as one of the most poorly mapped deep zones in any ocean. That is a striking thing to learn. In an era of satellites and
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In 2017, the Nippon Foundation and GEBCO launched the Seabed 2030 project, an ambitious international effort to map the entire global seafloor in high resolution by the year 2030. When researchers assessed which parts of the deep ocean were least known, the Diamantina region came up as one of the most poorly mapped deep zones in any ocean. That is a striking thing to learn. In an era of satellites, autonomous underwater vehicles, and global scientific collaboration, there are still places this large, this deep, and this close to a major continent that remain fundamentally unmapped and unstudied.
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Because it is a fracture zone rather than a subduction trench. The seafloor at the bottom of the Diamantina Deep is old, very old. The oceanic crust in this region is estimated to be somewhere between 80 and 100 million years old.
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Part of what makes the Diamantina interesting beyond the sheer depth is its geological character. Because it is a fracture zone rather than a subduction trench, the seafloor at the bottom of the Diamantina Deep is old, very old. The oceanic crust in this region is estimated to be somewhere between 80 and 100 million years old, formed at a mid-ocean spreading ridge and then carried northward as the Indo-Australian plate moved over geological time. That old crust has a different texture, a different mineral composition, and a different relationship with the water above it compared to the younger crust found at subduction trenches. Whether that geological character creates a different biological environment is something no one has yet been able to answer properly, because no one has looked carefully enough.
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subduction trenches. Whether that geological character creates a different biological environment is something that no one has yet been able to answer properly because no one has looked carefully enough.
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The pressure at the bottom of the Diamantina Deep is approximately 800 atmospheres. That means 800 times the pressure that you and I are sitting in right now. It is the kind of number that is easy to say and very difficult to actually imagine. At that pressure, water behaves slightly differently than it does at the surface. The density changes. Sound travels through it at different speeds. The body of any organism not specifically adapted to those conditions would be crushed instantly and completely.
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imagine. At that pressure, water behaves slightly differently than it does at the surface. The density changes. Sound travels through it at different speeds.
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And yet, in every other hadal zone where
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And yet in every other Hadal zone where scientists have looked, life exists. Not despite the pressure, but alongside it and in some cases because of it. What lives in the Diamantina Deep right now tonight as you are listening to this is
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genuinely unknown. Not unknown in the way that we suspect one or two species might have been missed. Unknown in the sense that no systematic biological survey of the deepest zone has been conducted.
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Whatever is down there has been living in that darkness under that pressure, in that cold for an enormous stretch of time, completely undisturbed by human curiosity.
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The organisms there, if they follow the pattern seen in other Hadal systems, have likely been evolving in isolation for millions of years, shaped by conditions specific to this fracture zone, this ocean basin, this particular corner of the deep earth. There is
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something about that idea that takes a moment to settle. We are not talking about a distant planet or a hypothetical environment. We are talking about a place on this earth reachable in principle from a port in Western Australia that contains life we have
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never seen. Life that has never been photographed, never been named, never been described in a scientific paper.
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Life that exists entirely outside the boundary of human knowledge. Not because it is rare or faint or difficult to detect in principle, but simply because we have not yet gone to look. That is the central tension of the dearantina
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deep. It is not a mystery in the sense of something lost or hidden. It is a mystery in the simpler, quieter sense of something that has simply not been looked at yet. And the longer you think about what might be down there, the more
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interesting the question becomes to understand why the Diamantina might hold life unlike anything found anywhere else. It helps to understand something about how the deep ocean is structured, how pressure and temperature and darkness change as you descend, and what
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that means for the creatures that have made their lives in those layers. Because the water column above the Diamantina Deep is not empty. It is a series of worlds stacked on top of each other, each one colder and darker and
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more pressurized than the last. Each one home to organisms that could not survive in the layer above or below.
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And at the very bottom of all of it, in the Hadal zone below 6,000 m, something is waiting that no human being has ever looked in the eye. That is where we are going next to understand the Diamantina
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deep as a place. You first have to understand what made it, and that means going back a very long way.
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Not to the 1960s when a converted Australian frigot lowered its echo sounder into the water and recorded a number that nobody quite expected.
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Further back than that, back to a time when the seafloor that now sits at the bottom of this deep was still being formed, still cooling, still hardening into the old oceanic crust it would carry for the next 100 million years.
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The Diamantina fracture zone is part of a system of geological features that formed as the great tectonic plates of the southern hemisphere began to rearrange themselves after the break up of the superc continent Gonduana. The Indo-Australian plate carrying the land
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masses of India and Australia began moving northward over geological time driven by the slow churning of the mantle beneath it. As it moved, it did not slide cleanly or simply. tectonic plates rarely do. Instead, different sections of the plate moved at slightly
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different rates in slightly different directions, and the boundaries between those sections became zones of shearing and fracturing, places where the crust was pulled apart and offset along what geologists called transform faults.
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Transform faults are not the same as the subduction zones that create the deepest trenches in the Pacific. In a subduction zone, one plate dives beneath another and the trench forms at the leading edge of that descent. The Mariana trench, the
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Java trench, the Tonga trench, these are all products of subduction. The Diamantina fracture zone was made differently. It formed along a transform fault system, a lateral shearing boundary. And the result is not a single clean trench, but a long complex series
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of parallel ridges and depressions running roughly east to west across the seafloor. The fracture zone stretches for approximately 2,500 km in that eastwest direction, which is a remarkable distance. If you placed it over a map of the continental United
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States, it would reach from the Atlantic coast well past the Mississippi River. What this structure means in practical terms is that the topography of the diamantina fracture zone is not simple.
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It is not a neat V-shaped groove in the seafloor. It is a corrugated complicated landscape of ridges and troughs and escarments where the seafloor rises and falls by thousands of meters over relatively short horizontal distances.
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The walls of the deepest sections are steep and fractured, composed of old basalttic crust that has been deformed and offset by millions of years of geological stress. Mapping this kind of terrain is genuinely harder than mapping a straightforward subduction trench
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because the sonar returns from irregular angled surfaces are more difficult to interpret cleanly. The complexity that makes the Diamantina geologically interesting is also part of what makes it logistically difficult to study. The oceanic crust at the bottom of the
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Diamantina Deep is old in a way that is worth dwelling on for a moment.
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Estimates place it at somewhere between 80 and 100 million years old. To put that in some kind of perspective, that crust was forming while dinosaurs were still alive. It was created at a mid ocean spreading ridge where magma wells
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up from the mantle and solidifies into new seafloor and then it was carried northward by the movement of the Indo-Australian plate over the following tens of millions of years until it arrived at its current position. Old oceanic crust is denser than young crust
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which is part of why it sits so deep. It has had a very long time to cool, to compact, to accumulate sediment, and to develop whatever chemical and mineral character it now has. That old crust is covered in most of the Diamantina region
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by a layer of sediment. In the deeper sections, that sediment is primarily salicious ooze composed largely of the tiny skeletal remains of microscopic organisms, datms, and radolarans that once lived in the sunlit waters far above. and slowly sank after they died.
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Over millions of years, this material accumulates in layers, and those layers preserve a record of the biological and chemical history of the overlying ocean.
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Sediment calls from parts of the fracture zone have been collected and analyzed, and they tell a story of sustained biological productivity in the waters above, which means there has been a slow but continuous rain of organic material falling toward the deep floor
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for a very long time. That rain of organic matter is in most deep sea systems the foundation of the food web.
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It is what had ecosystems are built on. Now at 8,000 m, the pressure pressing down on that seafloor is approximately 800 atmospheres. The figure is worth sitting with for a moment because it is one of those numbers that the mind tends
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to accept without really processing. One atmosphere is the pressure of the air around you right now. It is what you have always lived in and your body is built to function within it. 800 atmospheres is 800 times that. At that
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pressure, the compressibility of seawater itself becomes measurable. Water is generally treated as incompressible for most practical purposes. But at 8,000 m, it is noticeably denser than it is at the surface. The speed of sound through it changes. The behavior of gases dissolved
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in it changes. Everything about the physical environment at that depth is different from what we experience as normal. And yet life in every comparable environment that has been examined has found a way to persist. The reason pressure does not simply kill everything
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is that life at depth is not trying to resist the pressure from the outside. It has adapted to exist within it.
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The cells of hadal organisms are filled with fluid at the same pressure as their environment. They are not hollow spaces waiting to be crushed. They are structures that have evolved over millions of years to function at 800 atmospheres the way your cells function
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at one. The proteins in their bodies, the enzymes that drive their chemistry, the membranes that surround their cells, all of these have been shaped by natural selection to work under conditions that would destroy a surface organism instantly.
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It is not magic. It is just evolution given enough time and enough isolation. The isolation part is important and it connects directly back to the geology.
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The Diamantina fracture zone sits in the eastern Indian Ocean, separated from the Pacific Hadal systems by the entire Australian continent and the shallow seas around it and separated from other Indian Ocean deep zones by mid ocean ridges and the general circulation
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patterns of the deep water. The fracture zone is not a connected corridor to anywhere. It is in geological terms a closed system. Water enters from the surrounding ocean, but the topographic barriers created by the ridges within the fracture zone mean that the deepest
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sections are relatively isolated from one another and from the broader deep ocean circulation. This kind of isolation maintained over tens of millions of years is exactly the condition under which distinct species evolve. It is the same logic that
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explains why the animals of Australia are so different from those of Africa or South America. separation, time and different local conditions produce different life. The fracture zone's complexity also means that different sections of it exist at different depths
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and therefore under different conditions. The deepest point at approximately 8,047 m is not representative of the entire system. There are sections of the fracture zone that sit at 4,000 m, at 5,000, at 6,000. Each of those depth ranges corresponds to a different
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pressure regime, a different temperature, a different oxygen level, and potentially a different community of organisms.
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A thorough biological survey of the Diamantina would not be a single lander drop at the deepest point. It would be a series of deployments across the full depth range of the system, building a picture of how life changes as you
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descend from the abyssal plane into the Hadal zone. That kind of survey has not been done. Not even close. There is another consequence of the fracture zone's geological character that is worth mentioning, and it has to do with
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the walls themselves. The steep escarpments of the Diamantina fracture zone expose old oceanic crust directly to the water column. In some fracture zones, this exposure creates conditions for a particular kind of chemical reaction called serpentinization, where seawater interacts with certain
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iron and magnesiumrich rocks and produces hydrogen gas as a byproduct. Serpentinization is interesting to biologists because hydrogen is an energy source. Certain chemoliththotrophic microorganisms bacteria and archa that live on chemical energy rather than sunlight can use hydrogen to fuel their
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metabolism. This is the same basic principle that underlies the extraordinary ecosystems found at hydrothermal vents. Though fracture zone serpentinization tends to be lower temperature and lower energy than a true vent system.
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Whether the walls of the Diamantina fracture zone support any chemolithotrophic communities is genuinely unknown. The chemistry of the exposed rock surfaces there has not been studied in any systematic way. It is possible that there are microbial communities clinging to those ancient
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basaltt walls that derive their energy from the rock itself independent of anything happening in the sunlit waters above. That would be remarkable. It would also be entirely consistent with what has been found in other geological settings where old oceanic crust is
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exposed to seawater. The temperature at the bottom of the diamantina deep is approximately 1 1/2 to 2°.
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This is cold but not dramatically different from other hadal environments. The deep ocean is uniformly cold across most of its extent because the bottom water of the world ocean is formed primarily in polar regions where surface water chilled by contact with cold air
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becomes dense enough to sink to the seafloor and spread outward. In the Indian Ocean, this bottom water is supplied largely by Antarctic bottom water, a dense, cold, well oxygenated water mass that forms along the continental margins of Antarctica and
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flows northward along the seafloor. As it travels northward into the Indian Ocean, it gradually mixes with other water masses and changes its character.
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By the time it reaches the latitude of the Diamantina fracture zone, it has been modified somewhat from its original Antarctic composition. The oxygen content in particular tends to be lower in the Indian Ocean deep than in comparable Pacific depths, a consequence
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of the Indian Ocean's more restricted circulation and the longer time the deep water spends isolated from the surface before it is refreshed.
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That lower oxygen content is one of the factors that makes the Diamantina biologically distinct from Pacific hadal zones and it is one of the reasons that simply transplanting expectations from the Mariana Trench to the Diamantina deep would be a mistake. What the
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geology ultimately gives us is a setting, a very specific, very unusual, very old setting. A long fracture in old oceanic crust running east to west across the floor of the eastern Indian Ocean dropping at its deepest point to
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more than 8 km below the surface under 800 atmospheres of pressure at near freezing temperatures covered in salicious ooze and old sediment walled by ancient basaltt isolated from other deep systems by thousands of kilome of ocean and the geological barriers of mid
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ocean ridges That is the stage. It has been set for tens of millions of years.
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Whatever organisms have found their way into this environment and adapted to its specific conditions have had an enormous amount of time to become something genuinely their own. The geology does not tell us what lives there. It cannot.
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But it does tell us something important about the conditions that life would have to navigate. And it tells us that those conditions are specific enough and isolated enough that whatever has adapted to them is unlikely to be identical to what has been found
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anywhere else. The fracture zones complexity, the old crust, the particular chemistry of the Indian Ocean deep water, the long isolation, these are not just background details. They are the forces that would have shaped every organism in the Diamantina deep
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over millions of years of evolution. They are the reason that when someone finally does lower a camera to the bottom of this place, what appears in the frame may be something that no one has ever seen before and that does not
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match any description in any scientific catalog. But before we can talk about what might live there, it helps to understand what the journey downward actually looks like. Cuz the deep floor of the Diamantina is not reached in one
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step. It is reached through a series of layers. Each one a distinct world. Each one filtering the light and warmth and oxygen of the surface into something progressively more extreme. The water column above the diamantina deep is not
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simply a column of water. It is a stack of environments and understanding those environments is part of understanding why the bottom is what it is. If you start at the surface of the Indian Ocean above the Diamantina deep on a calm day
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somewhere southwest of Perth, the water looks blue and ordinary. There might be a swell running a few white caps. The kind of open ocean that stretches to every horizon without any feature to break it. Beneath the hull of a ship, it
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looks like nothing in particular. There is no visible sign that the seafloor below is among the deepest places on the planet. The surface gives nothing away.
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But drop something into that water and watch it sink and the story changes almost immediately. The first 200 m or so below the surface make up what oceanographers call the fotic zone or the sunlit zone. This is where
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photosynthesis happens. Sunlight penetrates well enough here to support phytolanton. the microscopic algae and cyanobacteria that form the foundation of almost every marine food web on Earth. The water in the Indian Ocean sunlit zone is warm at the surface
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somewhere around 25 to 28° C in the lower latitudes, though at the latitude of the Diamantina.
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Further south and closer to the influence of the Southern Ocean, surface temperatures are cooler, perhaps 15 to 18° C, depending on the season. This is where fish school, where zup plankton graze, where dolphins and seabirds operate. It is the part of the ocean
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that most people picture when they think of the sea. It is also a relatively thin skin stretched across an enormous depth.
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200 m sounds like a lot until you remember that the Diamantina floor is more than 8,000 m down. The sunlit zone is less than 3% of the total depth.
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Below 200 m, the light begins to fail. Not all at once, but gradually. The blue darkening into a dimmer blue, then into something closer to indigo, and then into a darkness that is not quite complete, but is close enough to it.
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This is the Messopelagic Zone, sometimes called the Twilight Zone, which runs from roughly 200 to 1,000 m.
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Temperatures here drop significantly. By 500 meters in the Indian Ocean, the water temperature might be somewhere around 8 to 10° C. And it continues to fall as you descend. There is still a faint trace of light at the shallower
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end of this zone. Enough that some organisms have evolved extremely sensitive eyes to detect it. But by the time you reach 900 or 1,000 m, even that trace is gone. Bioluminescence becomes the dominant form of light here. Many of
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the animals in the twilight zone produce their own cold blue green light, using it for communication, for camouflage against the faint surface glow above, for attracting prey or for confusing predators, lantern fish, hatchet fish, siphonophores that trail luminescent
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tentacles for meters through the water. It is a strange, dim, flickering world, and it is far more densely populated than most people realize.
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One of the more significant features of the Indian Ocean's water column sits within and just below the Mesopagic zone. It is called the oxygen minimum zone, and in the Indian Ocean, it's particularly pronounced. As organic material sinks from the sunlit zone
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above, it is decomposed by bacteria. And that decomposition consumes oxygen. In parts of the ocean where the water is not well circulated and refreshed from above, this bacterial consumption can deplete dissolved oxygen to very low levels across a substantial depth range.
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In the Indian Ocean, the oxygen minimum zone is one of the most severe in any ocean with dissolved oxygen concentrations dropping to levels that most fish and larger invertebrates cannot tolerate. It typically sits somewhere between roughly 200 and 1,000
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m, though its exact boundaries shift with location and season. What this means biologically is that the Indian Ocean's midwater is not simply a gradient of increasing pressure and darkness. It has an additional filter built into it, a layer where the
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chemistry itself becomes hostile to many forms of life. Organisms that live above this zone and organisms that live below it are effectively separated by a chemical barrier as real as any physical wall. This is one of the reasons that
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the Indian Ocean's deep fauna may be structured differently from what you find in the Pacific where oxygen minimum zones exist but tend to be less extreme.
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Below 1,000 m, you enter the bathopagic zone, the midnight zone from 1,000 to 4,000 m. There is no light here at all.
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Not even the faintest trace from the surface. The only light that exists is biological. Temperatures continue to fall, leveling off somewhere around 2 to 4° C across much of this depth range.
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Pressure at 1,000 m is already about 100 atmospheres. 100 times the pressure at sea level. At 2,000 m, it is 200 atmospheres. At 4,000 m, it is 400.
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These are not abstract numbers. 400 atmospheres means that every square cm of surface area is bearing a force equivalent to roughly 4 metric tons pressing down on it. The organisms that live here have not merely tolerated this pressure. They have built their entire
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biochemistry around it. Their cell membranes, their enzymes, their proteins, all of it has been shaped by evolution to function correctly under conditions that would instantly crush or disable the biology of any surface creature. The food supply in the
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midnight zone is thin and irregular. There is no photosynthesis down here. No primary production. Everything that lives here depends on what sinks from above. Marine snow, the gentle continuous rain of organic particles, dead cells, feal pellets, shed mucus,
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fragments of organisms drifts downward through the water column from the sunlit zone. By the time it reaches 2 or 3,000 meters, much of its organic content has already been consumed by bacteria and midwater organisms. What arrives at depth is often just the remnant, the
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least digestible fraction. Some larger food falls also occur. The bodies of dead whales, giant squid carcasses, fish that die and sink. These create intense temporary pulses of nutrition in an otherwise food poor environment.
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Organisms in the midnight zone have evolved to be extraordinarily efficient with energy, often moving slowly, having very low metabolic rates, and being capable of surviving long periods between meals. Some deep sea fish in this zone have been estimated to eat
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only a few times a year. Below 4,000 m is the abyssopelagic zone, the abyss, running from 4,000 to 6,000 m. By this point, the water temperature is close to its minimum, hovering around 1 1/2 to 2° C. Pressure is between 400 and 600
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atmospheres. This is the open water above the abyssal plane, the broad, relatively flat expanses of seafloor that cover much of the deep ocean. The abyssopelagic zone is sparssely populated compared to the zones above it, but it is not empty. Sea cucumbers
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drift slowly through the water. Certain species of deep sea fish patrol these depths. Amphipods, the small crustaceans that are among the most successful animals in the deep ocean, are present here in numbers that would surprise most people. They're tough, adaptable, and
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seem almost indifferent to the extremes of pressure and cold that define this environment. And then below 6,000 m, the Hadal zone begins. The word Hadal comes from Hades, the Greek underworld. It is an appropriate name. The Hadal zone is
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defined not just by depth, but by a particular kind of geography. It refers specifically to the water column and seafloor within deep trenches and elongated depressions that extend below 6,000 m. These are places where the seafloor drops away from the surrounding
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abyssal plane, creating enclosed or semi-encclosed basins with their own distinct physical and biological character.
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The diamantina deep with its maximum depth of approximately 8,047 m sits firmly in the hadal zone. The water column from 6,000 m down to the floor, a descent of more than 2 km below the already extreme abyss is a place of
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intensifying pressure, near freezing temperatures, near total darkness, and a food supply that is even more attenuated than in the zones above. At 8,000 m, the pressure is approximately 800 atmospheres. To put that another way, if you took a sealed air fil container to
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that depth, the pressure would compress it to roughly 1/800th of its original volume. The enzymes that drive biochemical reactions in most organisms begin to malfunction under this kind of pressure. Because pressure distorts the shapes of protein molecules, and protein
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shape is essential to protein function. Organisms that live in the hadal zone have evolved specific molecular adaptations to compensate for this. One of the most wellstudied is the accumulation of a molecule called trimethylamine oxide or TMAO in the
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tissues of hadal fish. TMAO acts as a piselite, a molecule that stabilizes proteins against pressure induced distortion.
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The deeper a hadal fish lives, the higher its TMAO concentration tends to be. This has an interesting practical consequence. At a certain depth, around 8,000 m or so, TMAO concentrations in fish tissues become so high that they begin to create their own osmotic
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problems, essentially limiting how deep fish can survive. This is one reason why the deepest fish ever recorded, a snail fish observed at approximately 8,336 m in the IUSawara trench in 2023 may be close to the absolute depth limit for
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vertebrate life. What this means for the diamantina is that its floor at just over 8,000 m sits right at the boundary of where fish can survive. Whether any fish have managed to colonize the deepest sections of the diamantina is
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genuinely unknown. The chemistry of the Indian Ocean deep water with its somewhat lower oxygen levels compared to Pacific had zones adds another variable. It is possible that the combination of extreme pressure and reduced oxygen at the Diamantina deep creates conditions that are more
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limiting for fish than the equivalent depth in the Mariana Trench. It is also possible that Indian Ocean adal fish have adapted to lower oxygen in ways that Pacific species have not. No one has looked. There is no footage, no
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collected specimen, no Edna sample from the had depths of the Diamantina to answer the question. The floor itself when you finally reach it is covered in sediment. In the case of the Diamantina, sediment cores from the broader region
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suggest a mixture of salicious ooze formed from the accumulated skeletal remains of tiny silica secretreting organisms called radolarans and datms that sink from the productive waters above and fine clay. This sediment layer is soft and deep built up over millions
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of years of slow accumulation. It is also in hadal systems generally surprisingly rich in organic material.
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The funnel geometry of a deep depression tends to concentrate sinking particles. Material that drifts down through the water column and lands near the edges of the depression can slide down the walls and accumulate on the floor. This concentrating effect means that had
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sediments often contain more organic carbon than the surrounding abyssal plane, which in turn supports higher densities of organisms, particularly microbes, than you might expect given how remote and extreme the environment is. The temperature at the bottom of the
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Diamantina is close to 1 1/2 to 2° C, as mentioned, cold, but stable. The deep ocean does not experience seasons in the way the surface does. The temperature at 8,000 m in the Indian Ocean today is almost certainly within a fraction of a
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degree of what it was 100 years ago or a thousand years ago. The darkness is absolute and permanent. The pressure is constant. In some ways, the Hadal zone is one of the most stable environments on Earth. Change happens there, but it
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happens slowly over geological time scales driven by shifts in deep ocean circulation, by changes in the productivity of the surface waters above, by occasional geological events.
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For organisms adapted to this stability, even small changes can be significant. Each of these layers, the sunlit zone, the twilight zone, the midnight zone, the abyss, the hadal, is populated by communities of organisms that are specifically adapted to its conditions
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and largely unable to survive in any other layer. A lantern fish from the mesopelagic zone would not survive at 4,000 m. A rattail fish from the abyssal plane could not function at 8,000 m. And whatever organisms live on the floor of
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the Diamantina deep are adapted to conditions that exist nowhere else on the surface of the planet. They are in a very real sense isolated by the layers above them just as surely as they are isolated by distance from other hadal
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systems. The water column is not just the path to the deep. It is a series of barriers. Each one filtering out organisms that cannot handle what comes next. until only the most specialized, the most pressure adapted, the most
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biochemically unusual life forms can exist in the space that remains at the bottom. This layered structure is part of what makes Hadal biology so interesting and part of what makes the Diamantina so compelling as an unexplored system.
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The conditions that exist on its floor have been shaped not just by depth and pressure, but by the specific character of the Indian Ocean's water column above it, including the pronounced oxygen minimum zone at mid depths, the particular temperature profile, the
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organic flux from the surface waters, which are themselves influenced by the Indian Ocean's distinct circulation patterns. The Diamantina's floor is not just deep. It is deep in a specific way in a specific ocean with a specific history of water flowing over it and
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organic material raining down into it over millions of years. And the organisms that have colonized it and adapted to it have done so under exactly those conditions. Not the conditions of the Mariana Trench, not the conditions of the Kerdc, but these conditions here
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in the eastern Indian Ocean in this long narrow fracture in old oceanic crust. To understand what might live there, it helps to look at what we actually know about Hadal biology in the systems that have been studied. Because while the
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Deamantina remains almost entirely unknown, other deep trenches have been visited, sampled, and cataloged. And what has been found in those places tells us something important about what the Diamantina might be hiding. So let us go back to the beginning of what we
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actually know about the Diamantina deep. Not the biology, not the speculation, but the simple act of measuring it.
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Because before anything else could happen, someone had to find it. The ship was H M A S Diamantina, an Australian Royal Australian naval vessel with a history that stretched back to the Second World War. She had been built
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as a riverclass frigot, one of the workh horses of the wartime Allied fleet, designed for convoy escort and anti-ubmarine patrol in the cold waters of the North Atlantic.
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After the war, the Diamantina was converted for a very different purpose. Her weapons were removed, her internal spaces were reconfigured, and she was recommissioned as a survey vessel tasked with the slow, methodical work of mapping the seafloor around the
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Australian continent and the surrounding ocean. It was unlamorous work by the standards of wartime naval service, but it was important. The seafloor beneath the Indian Ocean was in 1960 still largely a mystery. The broad outlines were known, but the details, the ridges, the
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fracture zones, the deep depressions remained poorly charted. In 1960, during one of these survey voyages, the Diamantina was operating in the eastern Indian Ocean, southwest of the Australian continent, in a region that even today sees relatively little ship
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traffic. Using an echo sounder, a technology that works by sending a pulse of sound down through the water and measuring how long it takes to return from the seafloor, the crew recorded a depth reading that was significantly deeper than the surrounding seafloor.
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The position was approximately 35° south latitude, 105° east longitude. The depth recorded was approximately 8,047 m. It was one of the deepest soundings ever recorded in the Indian Ocean. Echo sounding by 1960 was a reasonably mature technology. The basic principle had been
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in use since the 1920s and naval and oceanographic vessels had been using it to profile the seafloor for decades. But it was not perfect. The speed of sound in seawater varies with temperature, salinity, and pressure. and early echo
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sounders used fixed assumptions about that speed when calculating depth from the travel time of the pulse. This meant that the raw depth readings from early surveys often needed correction and the exact depth of the Diamantina deep has been refined over time as better data
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and better correction methods became available. The figure of 8,047 m is the most commonly cited value, though some sources give slightly different numbers depending on which corrections were applied and which survey is being referenced. What is not in doubt is the general scale of it.
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This is a place that extends more than 8 km below the ocean surface. The ship gave the feature its name and the name stuck. The Diamantina deep in the Diamantina fracture zone measured by HMA S Diamantina.
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There is something quietly satisfying about that. A piece of geography named for the vessel that found it. The way so many features of the deep ocean carry the names of the ships that first sounded them. What happened after that
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initial discovery is where the story becomes in a certain sense frustrating. Subsequent voyages did return to the region. Australian and international survey vessels refined the baimetric picture of the diamantina fracture zone over the following decades. Building a more detailed map of the ridges and
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troughs and the general topography of the area. The technology improved. Multi-beam sonar systems, which send out a fan of acoustic beams rather than a single pulse and can map a wide swath of seafloor in a single pass, replace the
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older single beam echoers and allowed for much higher resolution mapping. The picture of the Diamantina fracture zone became somewhat clearer, but the biological question was largely left alone. The surveys that followed the Diamantina's initial sounding were focused on bethimemetry, on the shape of
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the seafloor, not on what lived on it or in the water above it. No biological sampling equipment was deployed into the deepest sections of the depression. No cameras were lowered to the 8,000 m floor. No sediment cores were taken from
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the Hadal zone. The depth was measured and recorded. And then in terms of biological science, the Diamantina deep was essentially set aside. To understand how unusual this is, it helps to compare it to the Challenger Deep in the Western
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Pacific, which is the deepest known point in any ocean at approximately 10,900 m in the Mariana Trench. The Challenger Deep was first sounded in 1875 by HMS Challenger during the famous Challenger expedition that is often credited as the
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founding voyage of modern oceanography. Since then it has been visited repeatedly. Jacqu Picar and Don Walsh descended to the bottom in the Biscoff Triest in 1960. The same year hmas Diamantina was recording its depth sounding in the Indian Ocean. James
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Cameron made a solo dive there in 2012. The Five Deeps expedition visited in 2019. Numerous unmanned landers have been deployed, collecting sediment, filming organisms, measuring water chemistry. The Challenger Deep has been visited by crude submersibles more than a dozen times and by uncrrewed systems
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many more times than that. The Diamantina Deep has had zero crude descents, not one. No submersible, crude or uncrrewed, has been sent to its floor with the specific purpose of biological investigation. The depth has been measured. The general shape of the
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fracture zone has been sketched. And that is essentially the sum of what direct human exploration has contributed to our knowledge of the Dantina Deep since 1960. This is not an obscure footnote. The Diamantina deep is one of the deepest points in the entire Indian
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Ocean which covers roughly 70 million km and is the third largest ocean on Earth.
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It is a major geographical feature by any reasonable standard and yet it has received less dedicated scientific attention than many far shallower and less remarkable parts of the seafloor.
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The gap in our knowledge was formally acknowledged in the context of the Nippon Foundation and GEBCO Seabed 2030 project, an international initiative launched with the goal of producing a complete highresolution map of the entire global seafloor by the
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year 2030. When the project began assembling existing baimetric data to identify where the largest gaps were, the Diamantina region was identified as one of the least mapped deep zones in any ocean. The data coverage was sparse, the resolution was low, and the deepest
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sections of the fracture zone remained poorly characterized even in terms of basic shape and depth, let alone biology.
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Seabed 2030 has made progress since then. Vessels contributing data to the project have improved the coverage of the broader region. But mapping the shape of the seafloor and actually exploring what lives on it are two entirely different things. A multi-beam
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sonar survey can tell you that there is a depression 8 km deep at a particular location. It cannot tell you whether that depression is home to species of fish or crustation or worm that no biologist has ever seen. Those are
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questions that require a different kind of expedition entirely. One that brings cameras and sampling equipment down into the dark. The contrast with other Hadal systems is striking when you lay it out plainly.
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The Mariana Trench has been visited dozens of times. The Kerdc Trench northeast of New Zealand has been the subject of multiple dedicated biological expeditions, including the work of Alan Jameson and his colleagues at Newcastle University, who have deployed freefall
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landers there repeatedly and collected remarkable biological samples. The Tonga Trench has been studied. The Puerto Rico trench in the Atlantic has been sampled.
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The Java Trench, which is actually the deepest point in the Indian Ocean at approximately 7,290 m, was visited by the Five Deeps expedition in 2019 and had cameras and landers deployed into it. Even the relatively obscure Malloy Deep in the
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Arctic Ocean, which is only about 5,500 m deep, has received more dedicated biological attention than the Diamantina.
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The Diamantina is deeper than the Java Trench. It is deeper than the Puerto Rico trench. It is one of the 10 deepest points in any ocean. And it has been from a biological standpoint almost entirely ignored. Part of this comes
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down to a simple matter of numbers. The total number of dedicated Hadal biological expeditions, meaning voyages that specifically targeted depths below 6 or 7,000 m with equipment designed to collect biological samples is genuinely small. Fewer than 30 such expeditions
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have taken place since the year 2000. The Hadal zone as a whole is chronically underststudied relative to its scientific importance. When the total pool of expeditions is that small, the allocation of those expeditions to specific targets matters a stormously
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and the Diamantina has simply not made the list. There is also the matter of location.
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The Diamantina Deep sits roughly 1100 km southwest of Perth in the Southern Indian Ocean. Getting a research vessel there requires a multi-day transit from the nearest port. The southern Indian Ocean is not a calm place. It sits in
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the latitudes that sailors historically called the roaring 40s where westerly winds blow almost continuously and sea states can be severe.
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Operating sensitive deep sea equipment in those conditions adds complexity and risk to an already logistically demanding kind of expedition. This is not an insurmountable obstacle. Research vessels operate in the southern ocean regularly and the Diamantina region is not as extreme as some of the waters
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further south, but it adds to the cost and the difficulty in ways that make funding bodies and expedition planners hesitate. and funding is the core of it.
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A focused biological expedition to the Diamantina deep, the kind that would deploy multiple landers at different depths within the fracture zone, collect sediment cores, run bait cameras, and gather water column samples for environmental DNA analysis would cost somewhere in the range of 1 to3 million
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US depending on the vessel, the equipment, and the duration. That is not an astronomical sum by the standards of large scientific infrastructure. It is comparable to the cost of a modest piece of laboratory equipment at a major research university.
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But in the world of deep sea biology, where funding is scarce and competition for ship time is fierce, it is enough to keep the dear mantina at the bottom of the priority list year after year. The result is a situation that is, when you
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think about it carefully, genuinely strange. We live in an era when space telescopes can photograph galaxies billions of light years away. When satellites can map the surface of Mars to a resolution of a few cm. when private companies are
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launching rockets into orbit on a routine basis. And yet, one of the deepest places on our own planet, in our own ocean, remains essentially unexplored in any biological sense. The number 8,047 m has been sitting in the scientific
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literature since 1960. We know the depth. We have known it for 65 years. We just do not know what is down there.
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There is something almost philosophical about that. We're very good at measuring things from a distance. Sounding the depth of the ocean with an acoustic pulse is in some ways a remote measurement. A number derived from the travel time of a soundwave, not from
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direct observation. We got the number. We wrote it down. We named the feature after the ship that found it. And then we moved on to other things, leaving the actual interior of that place untouched and unexamined.
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The Diamantina deep has been known to science for 6 and a half decades. And in that time, it has received less biological investigation than many tide pools on the Australian coast. There are undergraduate research projects with more comprehensive data sets than what
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exists for the Hadal zone of the Diamantina. That is not an exaggeration. It is simply the state of things. What makes this particularly interesting from a scientific standpoint is that the Diamantina is not just deep. It is geologically and oceanographically
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distinct from the had systems that have been studied. It sits in a different ocean with different water chemistry, different circulation patterns, different sediment characteristics, and a geological history that is entirely its own. The organisms that have colonized its floor, if any have, have
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done so under conditions that differ in meaningful ways from the conditions in the Marana or the Keradec or the Tonga.
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Whatever has evolved there has had a long time to diverge from its relatives elsewhere, shaped by the specific pressures of this specific place. to understand why that matters and why the biology of an unexplored Hadal zone is not just an interesting curiosity but a
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genuinely significant scientific question. It helps to look at what has been found in the Hadal systems that have been studied. Because the story of Hadal biology over the past few decades is one of repeated surprise. Repeated discovery of things that were not
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expected. Repeated demonstration that the deep trenches of the world are not barren deserts but complex living ecosystems. Each one with its own character and its own cast of inhabitants. And that story is the best evidence we have for what the Diamantina
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might be hiding. The best place to start that story is the Marana trench because the Mariana is the most studied hadal system on Earth and it sets the baseline against which everything else is measured. The Mariana sits in the
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western Pacific Ocean east of the Marana Islands and its deepest point, the Challenger Deep, reaches somewhere around 10,985 m depending on the survey. That depth is extraordinary.
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But what has made the Mariana scientifically valuable is not just its depth. It is the fact that researchers have gone back there repeatedly with increasingly sophisticated equipment.
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And each time they have come back with something new. And the cumulative picture that has emerged from those expeditions is one of a place far more alive than anyone initially expected.
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For a long time, the assumption about hadal zones was fairly simple. The pressure is crushing. The temperature is just above freezing. There is no light.
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Food is scarce. Surely the thinking went. Only the most minimal forms of life could persist in such conditions. a few bacteria, perhaps some hardy invertebrates clinging to the sediment.
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The deep trenches were imagined as biological wastelands, extreme environments that life had barely managed to colonize. That assumption turned out to be wrong in almost every particular. One of the organisms that dismantled that assumption most dramatically is a small crustaceian
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called Honda gigas. It is an amphipod, a shrimplike creature belonging to a group that is found throughout the ocean from the surface to the very deepest points.
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Here gigas is specifically aal species found in the Marana and several other deep Pacific trenches and it is not rare. It is abundant.
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Traps baited with fish and lowered to the floor of the Challenger Deep have come back packed with these animals.
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Sometimes hundreds of them crowding around the bait within hours of it reaching the bottom. They are small, typically a few cm long, pale and translucent with specialized adaptations that allow their cell membranes to remain flexible under pressures that
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would destroy the membranes of surface dwelling organisms. They have been found at depths exceeding 10,000 m. They are in their way extraordinary animals and they are just one species among many that have been documented in the hadal zone. Polyat worms are another hadal
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staple. These are segmented worms, bristled and often quite elaborate in their body plans and they appear in hadal sediments with remarkable regularity.
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Some species are deposit feeders, moving through the sediment and processing organic material. Others are predatory.
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They have been found in the Marana, in the KerdC trench northeast of New Zealand, in the Japan trench, in the Puerto Rico trench in the Atlantic. They seem to be a reliable component of hadal communities wherever sampling has taken
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place. Holyurans, which are sea cucumbers, also appear frequently in Hadal footage. These soft-bodied echinoderms move slowly across the seafloor, ingesting sediment and extracting organic matter. And they have been photographed in multiple trenches at depth exceeding 6,000 m. Some species
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appear to be quite large, even atal depths. Their pale, elongated bodies drifting slowly above the mud in bait camera footage. And then there are the snail fish. If there is a single group of organisms that has most captured the
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public imagination in recent biology, it is the snail fish, the family liparid. These are softbodied fish, not particularly dramatic to look at, pale and somewhat tadpole-shaped without the elaborate bioluminescent lures or the terrifying teeth of some deep sea
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species. They look honestly a bit unfinished, but they are remarkable for one simple reason. They hold the depth record for fish. In 2023, a snail fish of the species Pseudo Leperis belly was observed and recorded at a depth of
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8,336 m in the Izuara trench south of Japan, breaking the previous record. The Mariana's own snail fish, pseudoliperous swiri, has been documented at depths exceeding 8,000 m as well. These are vertebrates, animals with spines and skulls and fins and organs, living and
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apparently thriving at pressures that would collapse the body cavities of most fish entirely. They managed this through a combination of adaptations, including high concentrations of a compound called tramothylamine oxide or TMAO, which stabilizes proteins under pressure. The deeper the fish, the more TMAO in its
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tissues. And researchers have found that this relationship holds across species, suggesting a kind of chemical ceiling on how deep fish can go, somewhere around 8,500 m. beyond which the TMAO concentration required would itself become physiologically problematic. It is a fascinating constraint, a chemical
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limit written into the biology of vertebrates. And it means that whatever lives at the very deepest points of the hadal zone is almost certainly not a fish in the conventional sense. What all of these organisms share is a dependence
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on what oceanographers call marine snow. It sounds almost pretty the name and in a way the phenomenon is marine snow is the continuous slow fall of organic particles from the surface ocean downward through the water column. Dead phytolankton zup plankton fecal pellets
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shed mucus fragments of large organisms all of it drifting slowly downward taking days or weeks to reach the deep sea floor. By the time it arrives at Hadal depths, it has been partially consumed and decomposed by organisms in
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the layers above. So what reaches the bottom is a sparse, degraded trickle of energy. But trenches and deep depressions have a geometric advantage.
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Their shape acts like a funnel. Organic material that settles onto the sloping walls is channeled toward the deepest point, concentrating food at the bottom.
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This is one reason Hadal zones are not the barren wastelands they were once imagined to be. The trench geometry itself creates a local enrichment, a subtle accumulation of energy at the very bottom that supports higher organism densities than the surrounding
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abyssal plane. This funneling effect has been documented in multiple Hadal systems and is now considered a fundamental feature of Hadal ecology. It means that the deepest point of a trench or depression is not the most hostile point for life, but in some ways the
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most provisioned. The pressure is highest there, yes, and the temperature is cold and the darkness is absolute.
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But the food supply, such as it is, is better than on the flat abyssal plains nearby. That is a counterintuitive fact that took decades of observation to establish, and it matters for understanding what the dearantina might hold.
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Now here is where the geography becomes important. The organisms found in one Hadal system are not necessarily found in another. This is one of the most significant findings of comparative Hadal biology over the past two decades and it has direct implications for the
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Diamantina. When researchers began sampling multiple trenches systematically and comparing their forers, they found that the degree of overlap was surprisingly low. The Kerdc Trench, which runs northeast of New Zealand, and the Tonga Trench, which runs roughly parallel to it a few
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hundred km to the north, are geographically close by ocean standards. They're in the same general region of the southwestern Pacific, and yet their amphipod communities are distinct.
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Species found in abundance in one are absent or rare in the other. The same pattern holds when you compare the Keradec to the Marana or the Mariana to the Japan trench. Each system has its own assemblage. Each has species that
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appear to be endemic to that particular depression found nowhere else in the ocean. This is the principle of Hadal endemism and it makes intuitive sense once you understand the isolation involved. Hadal zones are separated from one another by vast stretches of abyssal
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seafloor at depths that are too shallow for true Hadal specialists and too deep for many abyssal species.
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The organisms that evolve to thrive at 8 or 9,000 m under the specific conditions of a given trench are not easily dispersed to another trench on the other side of an ocean basin. The mid ocean ridges, the abyssal plains, the
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different water masses and temperature regimes between ocean basins all act as barriers. Over millions of years, populations in separate hadal systems diverge. They accumulate genetic differences. They develop distinct physiological adaptations suited to their particular environment. They become eventually different species. The
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Kerdc Trench, which is one of the better studied Hadal systems, has been found to have a remarkably high proportion of endemic amphopod species. Studies published in the 2010s found that a significant fraction of the amphopod species collected from the Kerdc were
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not found in other trenches. Similar patterns have been documented for polyets and other invertebrate groups in various hadal systems.
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The snail fish of the Marana are different from the snailish of the Kerdc which are different from those found in the Japan trench. The lipid family has in a sense colonized the hadal zone multiple times in different ocean basins
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producing distinct species each time through a process of parallel evolution under similar but not identical conditions. What this means for the dearantina is not hard to see. The dear mantina deep sits in the Indian Ocean separated from the Pacific had systems
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by the vast Indo-Pacific ridge systems and by thousands of kilome of open ocean. Its geological history is distinct. Its water chemistry is distinct in ways that the next section will explore in more detail. Whatever colonized the Diamantina's deepest
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sections did so under Indian Ocean conditions using whatever source populations happen to be present in the southeastern Indian Ocean and those populations have been evolving in isolation under the specific pressures and temperatures and food supply conditions of this particular fracture
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zone for an extremely long time. The fracture zone itself is built on oceanic crust that is 80 to 100 million years old. The deep depression has existed in some form for tens of millions of years.
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That is an enormous span of time for populations to diverge, for adaptations to accumulate, for new species to emerge from ancestral forms.
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The honest scientific expectation based on everything known about hadal endemism and the factors that drive it is that the diamantina deep harbor species that are found nowhere else on earth not as a dramatic speculation but as a straightforward extrapolation from
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wellestablished biological principles. If every other Hadal system that has been examined carefully has turned out to have endemic species and if the Diamantina is more geographically and oceanographically isolated than most of those systems, then the probability that it also has endemic species is high. The
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question is not really whether unique organisms live there. The question is what they look like, how many there are, and how they have solved the specific challenges of their environment.
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Some educated guesses are possible based on what has been found in analogous systems. Amphopods are almost certainly present. They are found in every hadal zone that has been sampled. They're extraordinarily pressure tolerant and they are highly diverse at the species
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level. The amphipods of the diamantina would likely be distinct from those of the kerdc or the marana, possibly significantly so. Polyiti worms are another reasonable expectation.
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Holyurans, given their presence in virtually every deep sea environment that has been photographed, seem likely as well. Whether liparid fish are present is an interesting question. The snailfish depth record of 8,336 m is close to the diamantina's depth of
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8,047 m, which means the diamantina's floor sits within the known depth range of hadal fish. If the Indian Ocean has its own lineage of hadal lipids, which is plausible given the pattern of independent colonization seen in other ocean basins, the Diamantina could be
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home to a fish species that has never been observed. That is not a certainty.
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It is a possibility that the biology supports. What is closer to a certainty is that the Diamantina's microbial world is unique. But that is a subject that deserves its own careful attention because the microbial dimension of Hadal biology is in many ways the most
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surprising and the least appreciated part of the story. The large animals, the amphipods and the snailish and the sea cucumbers are what capture the imagination. They are visible, recognizable, relatable in their way. But the foundation of the Hadal ecosystem, the base of the food
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web, the organisms responsible for processing the organic matter that accumulates at the bottom are microscopic.
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And the microbial communities of Hadal sediments have turned out to be far more complex, far more active, and far more diverse than anyone expected. The Diamantina sediments composed primarily of celicus ooze and deep sea clay would support microbial communities shaped by
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the specific chemistry and organic input of the southeastern Indian Ocean. Communities that have likely been evolving in that environment for millions of years without any human awareness of their existence.
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Understanding what those communities look like and how they function would require going there. And to understand why going there matters even beyond the biology of large animals, it helps to look at what microbial research in other Hadal systems has already revealed. To
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understand why the Diamantina deep is biologically distinct from the Hadal zones of the Pacific, it helps to spend a moment with the water itself. Not just the pressure, not just the depth, but the actual movement and chemistry of the
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water that fills this part of the Indian Ocean. Because the deep water of the Indian Ocean behaves differently from the deep water of the Pacific, and those differences matter enormously for what can live at the bottom. The deep basins
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of the world's oceans are not filled with stagnant water. They are slowly, continuously flushed by a global circulation system driven primarily by density differences caused by temperature and salinity.
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Cold, dense water formed near the poles, sinks and spreads outward along the seafloor, gradually moving through deep basins over time scales of centuries to millennia.
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This process, sometimes called thermaline circulation, is what keeps the deep ocean oxygenated enough to support life. Without it, the deep basins would eventually become enoxic, depleted of dissolved oxygen, and most animal life as we understand it would not be possible there. In the Indian
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Ocean, this deep flushing is primarily accomplished by Antarctic bottom water. This is very cold, very dense water formed in the southern ocean near Antarctica where surface water chills to near freezing, becomes heavy and sinks.
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From there, it spreads northward along the seafloor, gradually filling the deep basins of the Indian Ocean. The process is slow. The water moving along the floor of the southeastern Indian Ocean today may have last been at the surface
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near Antarctica decades or even centuries ago. As it travels northward, it warms slightly, mixes with surrounding water masses, and gradually loses some of its original character.
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What matters for the Diamantina is that the Indian Ocean's deep circulation is more restricted than the Pacific's. The mid ocean ridge systems of the Indian Ocean, including the southwest Indian ridge, the southeast Indian ridge and the central Indian ridge, divide the
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ocean floor into a series of deep basins separated by topographic barriers. Water can flow between these basins, but only through gaps and passages at certain depths. This means that deep water renewal in the Indian Ocean is slower and less efficient in some
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regions than in the Pacific where the vast size of the basin and different ridge configurations allow somewhat freeration.
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The practical consequence of this is that dissolved oxygen levels in parts of the Indian Ocean deep are lower than in comparable Pacific environments. The Indian Ocean is well known among oceanographers for having one of the most pronounced oxygen minimum zones of
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any ocean. This is a layer of water typically sitting somewhere between about 200 and 1,000 m depth where dissolved oxygen drops to very low levels because biological consumption of oxygen in that zone outpaces the resupply from circulation.
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The Indian Ocean's oxygen minimum zone is particularly intense in some regions including parts of the eastern Indian Ocean near the Australian margin. Below the oxygen minimum zone, oxygen levels recover somewhat in the deep water, but the overall oxygen inventory in the
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Indian Ocean deep is generally lower than in the North Pacific or South Pacific at equivalent depths. For the Diamantina deep specifically, the dissolved oxygen concentration at the very bottom is not well characterized.
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That is one of the fundamental gaps in our knowledge. We do not have reliable measurements of the water chemistry at 8,000 m in the Diamantina. What can be inferred from the broader regional oceanography is that the oxygen levels
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are likely adequate to support animal life since Antarctic bottom water which supplies the deepest Indian Ocean basins is relatively well oxygenated when it forms.
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But how much oxygen persists after traveling through the restricted circulation of the southeastern Indian Ocean to reach the Diamantina's floor is genuinely uncertain. The temperature at the bottom of the Deamantina deep is estimated to be somewhere around 1 and
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12 to 2° C. This is consistent with what Antarctic bottom water typically carries into deep Indian Ocean basins and it is broadly similar to temperatures found in deep Pacific trenches.
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The Mariana Trench bottom water temperature is roughly in the same range around 1 to 2° C. So temperature alone does not sharply differentiate the Diamantina from Pacific Hadal environments. But temperature is only one variable among many. And the
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combination of temperature, pressure, oxygen availability, salinity, and sediment chemistry together shapes the biological community in ways that no single parameter captures. The salinity and chemical composition of the water filling the Diamantina also has a distinct Indian Ocean character. The
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Indian Ocean tends to be slightly saltier than the Pacific in its surface waters partly because evaporation exceeds precipitation over much of its area and this influences the density structure and mixing of the water column. At depth, the differences are
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smaller, but they are real and they affect the physiological environment that organisms must adapt to. Even small differences in iron concentrations in the ratio of particular dissolved minerals can matter for biological processes at the cellular level, particularly for organisms living at
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extreme pressure where membrane chemistry is already under stress. One of the more interesting aspects of the Diamantina's geological setting, is that it sits within a fracture zone rather than a simple subduction trench. The walls of the Diamantina fracture zone
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expose sections of old oceanic crust and upper mantle rock that have been tectonically uplifted and tilted over millions of years.
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These exposed rock surfaces composed partly of basaltt and partly of ultramafic rocks like peridotist can support chemoliththotrophic microbial communities. Chemithroofs are organisms that derive energy not from organic matter or sunlight, but from chemical reactions involving inorganic compounds, often minerals. They have been found
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colonizing exposed rock surfaces at mid ocean ridges and in other tectonically active deep sea environments.
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Whether similar communities exist on the walls of the Diamantina fracture zone is unknown, but the geological setting is not unlike environments where such communities have been discovered elsewhere. The sediment at the bottom of the diamantina is thought to consist
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primarily of salicious ooze and deep sea clay. Salicious ooze is composed largely of the silica based skeletons of microscopic organisms primarily datoms and radolarans that lived in the surface waters above and sank to the seafloor after dying. The presence of celicious
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ooze indicates that the overlying surface waters are biologically productive at least enough to generate a steady rain of organic particles sinking toward the deep. This is important for the Hadal food web because the organisms living at 8,000 meters depend almost
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entirely on this sinking organic material often called marine snow as their energy source. The fracture zone's elongated shape may also act as a topographic funnel, concentrating organic particles that drift in from the surrounding seafloor, just as has been
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documented in Pacific trenches. But the specific character of the organic material raining down over the Diamantina is different from what falls over the Marana or the Kerma deck. The biological communities in the surface waters of the southeastern Indian Ocean
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are distinct from those of the tropical Pacific. Different species of phytolanton, different zup plankton communities, different seasonal patterns of productivity shaped by the Indian Ocean's monsoon-driven circulation.
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What sinks is a product of what lives above. And so the food supply reaching the deer mantina's floor has a distinct Indian ocean flavor in a literal chemical sense. The ratio of different organic compounds, the types of fatty
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acids, the bacterial communities already working on the particles as they sink. All of this varies by region. and the organisms adapted to processing that particular food supply over millions of years would be shaped by its specific chemistry. There is another
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oceanographic feature worth noting. The Indian Ocean has only one opening to the north through the relatively shallow passages of the Arabian Sea and Bay of Bengal region and its southern boundary opens freely into the southern ocean.
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This semi-encclosed configuration means that the Indian Ocean's deep water does not exchange as freely with global circulation as the Pacific's does. Water that enters the deep Indian Ocean basins tends to stay there longer before being replaced. This longer residence time
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means that any chemical signals introduced into the deep water, whether from biological processes, sediment interactions or geological sources, have more time to accumulate and influence the environment. It is another way in which the Indian Ocean deep is not
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simply a copy of the Pacific Deep. The Java Trench, which is the deepest point in the Indian Ocean at approximately 7,290 m, has received more scientific attention than the Diamantina. Partly because it is a subduction trench associated with the geologically active
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Sunda Ark and partly because the Five Deeps expedition visited it in 2019. The biological samples and observations from the Java Trench have given scientists their first real look at Indian Ocean Adal fauna. And what was found was consistent with the
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expectation that the Indian Ocean Adal zone is biologically distinct from the Pacific. Snailfish were observed at around 7,192 m. Amphipods were collected. Holtherans were photographed. But the Java trench is not the Diamantina.
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It sits in a different part of the Indian Ocean under different surface water conditions within a different geological setting and at a somewhat shallower maximum depth. The species found there may or may not be present in the Diamantina and the Diamantina's
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greater depth, different sediment type and different regional oceanography would be expected to produce at least some differences in the biological community. The OB trench and the Vimma trench, two other Indian ocean deep features, received limited sampling by Soviet research vessels during the
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midentth century, primarily in the 1950s through 1970s. Those expeditions collected amphipods and polyets and documented some of the basic biological presence in Indian Ocean hadal environments. But the work was constrained by the technology of the era and was never followed up
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systematically. The dearantina was not among the sites visited even in those early surveys. It has remained outside the itinerary of every hadal biological program that has operated in the Indian Ocean. What this means is that we do not have a microbial
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baseline for the diamantina. We do not have a sediment chemistry profile for the deepest sections. We do not have oxygen measurements from the bottom. We do not have photographs of the seafloor.
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We do not know what the sediment surface looks like, whether it is smooth or biotubated, whether it shows signs of active biological reworking, whether there are visible organisms moving across it. We know the depth approximately and we know the broad
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regional oceanographic context and from that context we can make educated inferences. But the specific environmental parameters that would allow a biologist to predict with confidence what organisms might be present, those parameters are simply not measured. This is not a trivial gap. In Hadal biology,
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the environmental details matter enormously. The difference between a sediment oxygen level of 3 ml per liter and 1 ml per liter can mean the difference between a rich macroal community and a much simpler one. The difference between a
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particular type of clay sediment and solicious ooze affects which microbial communities dominate the bottom which in turn affects the food available to larger organisms.
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The specific pressure at a given depth affects which pressure adapted enzymes function and which do not, which shapes which organisms can survive there at all. Without knowing these parameters for the diamondina, we are working from analogy and inference, and analogy only
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goes so far when the system in question is genuinely novel. There is something quietly humbling about this. The Diamantina Deep is not hidden in any dramatic sense. It is not obscured by ice or jungle or political barriers. It
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sits in open international waters. Its coordinates are known. Its depth has been recorded for over 60 years. But the specific oceanographic conditions at its floor. The basic environmental facts that any ecologist would want to know before making predictions about the life
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there remain uncharacterized. It is a known unknown in the most straightforward sense of that phrase. We know that we do not know. We just have not yet gone to find out. Part of what makes this situation so interesting from
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a scientific standpoint is that the Indian Ocean Deep is not simply an understudied version of the Pacific Deep. It is a genuinely different environment shaped by different circulation patterns, different geological history, different surface productivity, and different isolation from other deep basins.
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The organisms that have evolved in Indian Ocean had hadal conditions have done so under a distinct set of selective pressures and the results of that evolution are not predictable simply by analogy with the Marana or the Kerdc. They have to be observed directly
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which brings the story naturally to the question of what has actually been observed in and around the Disantina region. Because while no dedicated Hadal expedition has ever reached the deeper sections of the Damantina fracture zone, there have been research voyages in the
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broader region and some of them did collect biological samples from the shallower parts of the fracture zone and the surrounding seafloor. Those samples are fragmentary. They are from the margins rather than the depths and they raise as many questions as they answer.
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But they are what exists and they offer at least a partial picture of the biological world that surrounds the deep even if the deep itself remains out of reach. The Australian research voyages that ventured into the broader Diamantina fracture zone during the
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1970s and 1980s were not for the most part dedicated deep sea biological expeditions. They were multi-purpose surveys. The kind of scientific work that covers a lot of ground without going especially deep into any single question. Cyro, the Commonwealth
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Scientific and Industrial Research Organization, operated several research vessels in the southeastern Indian Ocean during this period and some of their transcts passed through or near the fracture zone. When biological sampling was conducted, it typically involved troll nets deployed at depth, sediment
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corers dropped to the seafloor, and water column sampling at various depths. These are standard tools of oceanographic survey work, and they produced real data, just not data from the deepest part.
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The depths sampled during these voyages were in most cases in the range of 2,000 to 4,000 m. That is deep by most standards. It is dark, cold, and under considerable pressure. But it is not the Hadal zone. It is the abyssal zone, the
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broad mid-range of the deep ocean. And the organisms found there are a different community from the ones that would inhabit the 8,000 m floor of the Dantina itself.
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The troll samples recovered from these depths included fish from the family macroe which are commonly known as rat tails or grenine.
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Rat tails are among the most abundant deep sea fish in the world and finding them in the diamantina region is not surprising. They're generalists of the abyss present in deep water across all oceans and their presence in the
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fracture zone tells us that the basic conditions for large-bodied fish life exist in the region. But it does not tell us much about what might be happening 6,000 m deeper. Kuskils from the family of Fidi were also recovered
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in some of these trolls. This family is notable in Hadal biology because some of its members have been recorded at extreme depths in other oceans. The snail fish that have become famous for their record-breaking depth tolerance are lipids, not a fides, but cuskals are
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also capable of surviving at considerable depth. and some species have been collected from hadal zones in the Pacific. Finding aides in the shallower sections of the Diamantina fracture zone is at least consistent with the possibility that related or
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adapted species might exist deeper in the system. It is a suggestive data point, not a conclusion, but it is the kind of thing that a hadal biologist would notice. Crustations appeared in the trolls as well. Various species of
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deep sea amphipods, isopods, and other small crustations were collected from the abyssal sections of the fracture zone. Amphipods in particular are one of the most reliable indicators of what a hadal zone might support because they are the dominant macroal organisms in
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most studied halal systems and because they are known to be extremely diverse at the species level across different deep basins. The amphipods recovered from the diamantina region in these surveys were not identified to species level with a kind of careful taxonomic
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attention that would allow meaningful comparison to hadal amphipod fauna from other oceans. The samples were collected, the organisms were noted and the work moved on. That is the nature of multi-purpose survey science. You cover the territory and note what is there
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without necessarily having the time or resources to analyze everything in depth. Echinoderms were also present.
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Sea cucumbers, brittle stars, and sea urchins were recovered from sediment trolls and grabs at various depths within the fracture zone. Holtherans, the sea cucumbers are particularly relevant here because they are one of the most characteristic organisms of hadal sediment environments. In
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wellstudied trenches like the Mariana and Kerdc, herurans are among the most commonly photographed large animals on the seafloor, often seen moving slowly across the sediment surface, ingesting it as they go and extracting organic matter from it. Their presence in the
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shallower sections of the Diamondina fracture zone suggests that the regional Holyan fauna is present and active. And it raises the straightforward question of whether holyan species adapted to greater depth might exist in the deeper sections of the same system.
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What the sediment cause from the region added to this picture was a different kind of information. The cause showed sediment composition and what they revealed was a prevalence of salicious ooze in portions of the fracture zone particularly in areas influenced by the
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productivity of the overlying surface waters. Cissicius ooze is made up primarily of the silica based skeletons of datoms and radolarans tiny photosynthetic and heterotrophic plankton that live in the sunlit surface layer and when they die sink slowly to
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the bottom. The presence of this material in the sediment is an indicator that the surface waters above the diamantina region are biologically productive enough to generate a meaningful rain of organic particles downward.
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This matters for the Hadal zone because most of the energy available to organisms at 8,000 m comes from exactly this process. Marine snow, the slow continuous fall of organic material from above. If the surface productivity is sufficient to produce salicious ooze in
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the sediment record, that is a reasonable indication that the deep floor of the diamantina is not entirely starved of food. Forominapera were also abundant in the sediment cores.
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Ferominaphera are single-sellled organisms with shells and they are found in enormous numbers in deep sea sediments across all oceans. Their presence in diamantina region cores is not surprising. But the species composition of forominiferral assemblages can tell paleocanographers quite a bit about the history of water
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temperatures and circulation patterns in a region. Some of this work was done on the cause collected during the CSRO voyages and it contributed to the broader understanding of Indian Ocean Paleocanography for the purposes of understanding present-day biology in the deep. Foram
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minifera are also relevant because they are among the organisms that do persist at hadal depths. Living forum and ephera have been collected from the floors of multiple trenches and some species appear to be specifically adapted to extreme pressure conditions. It is worth
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pausing here to be clear about what all of this amounts to. The biological samples from the Diamantina region collected in the 1970s and 1980s are real data. They are not nothing. They established that the broader fracture zone supports a diverse abyssal fauna,
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that the sediment conditions are consistent with biological activity, and that the regional oceanographic setting is productive enough to supply organic material to the deep. In that sense, they are encouraging. They suggest that the Diamantina is not a biological
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desert in its shallower sections. And by reasonable extrapolation, they make it plausible that the deeper sections are inhabited as well. But they are samples from the entrance, not the interior. The difference between 4,000 m and 8,000 m in the ocean is not just a matter of
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degree. It is a categorical shift in the conditions of life. The pressure at 4,000 m is roughly 400 atmospheres. At 8,000 m, it is closer to 800. That doubling of pressure is not trivial. It changes which proteins can maintain
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their structure, which enzymes can function, which cellular membranes remain fluid rather than rigid. Organisms adapted to 4,000 m cannot simply extend their range to 8,000 m.
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The fauna of the abyssal zone and the fauna of the dal zone are distinct communities shaped by different selective pressures over long evolutionary time scales. So the rat tails and cusk eels and holtherans recovered from the shallower sections of
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the diamantina fracture zone are neighbors of the deep not inhabitants of it. They tell us something about the neighborhood. They do not tell us who lives at the bottom of the street. No Hadal lander has ever been deployed to
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the 8,000 m zone of the Diamantina deep. This is the central fact that shapes everything else about what we know and do not know. A hadal lander is a relatively simple device in concept. A weighted frame carrying instruments and
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bait. Dropped freely from the surface, allowed to sink to the bottom under gravity, left there for a period of allows to collect data and samples, and then released to float back up by dropping its ballast weight. The acoustic release mechanism that triggers
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the ballast drop is controlled from the surface ship. Modern landers of this type can carry bait cameras, sediment corers, water samplers, and environmental sensors. They are the primary tool by which had biology has been advanced over the past two decades
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and they have been deployed successfully in the Marana trench, the Kerdc trench, the Tonga trench, the Izu Aasawara trench and in 2019 the Java trench in the Indian Ocean. Not one of them has been sent to the Diamantina.
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There is no great mystery about why in one sense. The Diamantina is far from any major research port. The logistical cost of reaching it and operating there is significant and the scientific community that focuses on Hadal biology is small and its funding is limited. But
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the absence of even a single lander deployment at the deepest point of the Dear Mantina after more than 60 years since its depth was first recorded is still a striking fact when you sit with it for a moment. This is one of the
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deepest places in the Indian Ocean. It has been known to science since 1960 and we have never dropped a camera to its floor. What this means in practical terms is that the biological picture we have of the Diamantina deep is assembled
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from inference, analogy, and samples taken from depths that are genuinely different from the Hadal zone itself.
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The inference is reasonable. The analogy is grounded in real science. This samples are real data, but the actual floor of the Diamantina, the sediment surface at 8,047 m, the water column in the final 2,000 m of descent, the
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specific organisms that move through the dark at that depth. Those things have not been seen, not even once. There is something that feels almost counterintuitive about this, especially in an era when remote sensing satellites can image the surface of Mars at
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resolutions of a few cm and when the genomes of thousands of species have been sequenced and cataloged. The diamantina deep is on Earth. It is in the ocean. It is reachable with technology that exists and has been demonstrated to work. And yet it sits
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there unvisited at its deepest point, its floor unseen, its inhabitants unknown. The samples we have from the broader region are a glimpse through a window into a room that is adjacent to the one we actually want to enter. They tell us
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the building is occupied. They do not tell us what is inside the room at the end of the hall. What those samples do hint at though is that the biological world surrounding the Diamantina Deep is active and diverse enough to make the
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deep itself worth investigating. The rat tails and cusk eels of the abyssal sections suggest a functional food web operating in the water column and on the seafloor above the hadal zone. The holothorans and crustations recovered from sediment trolls indicate
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that the seafloor at intermediate depths supports communities capable of processing organic material. The salicious ooze and ferominifheral sediments point to surface productivity sufficient to maintain a supply of marine snow falling through the water column toward the bottom. These are the
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conditions that in other hadal systems support the communities of amphipods, snailfish, polyates and holtherans that have been documented in trenches like the Marana and the Keradec. The Diamantina has all of the surrounding context. It has the regional biology,
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the sediment type, the surface productivity, the geological structure. What it lacks is the direct observation.
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And in Hadel biology, direct observation is the only way to know what is actually there. Because the hadal zone is strange enough that extrapolation from neighboring depths routinely produces surprises. Every time a lander has been sent to a new Hadal system, it has found
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something that was not fully predicted. New species, unexpected abundances, behaviors that were not anticipated from what was known about related organisms in shallower water. The history of Hadal exploration is a history of being surprised by what is down there even
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when the general outlines were expected. This pattern of surprise, the consistent finding that each hadal system contains something that was not predicted from the surrounding environment or from analogous systems elsewhere is one of the strongest arguments for exploring
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the Diamantina specifically. Not just because it is deep, but because it is isolated, geologically distinct and situated in an ocean whose hadal biology remains almost entirely unknown.
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Whatever lives at the bottom of the Dear Mantina deep has had millions of years to diverge from its relatives in other oceans, adapting to the specific pressure temperature chemistry and food supply of that particular environment. The longer a population has
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been isolated, the more distinct it becomes. And the diamantina has been isolated for a very long time. This is the question that the fragmentaryary samples from the 1970s and 1980s raise without answering. They confirm that the biological world around the deep is real
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and active. They confirm that the sediment conditions are consistent with life. They confirm that the fracture zone is not a dead zone. But they leave the deepest section entirely uncharacterized. A blank space at the bottom of a system that is otherwise, at
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least in outline, biologically plausible. And the question of what fills that blank space, what specific organisms have evolved in the dark at 8,000 m in the Indian Ocean, what they look like, how they function, and whether they're found anywhere else on Earth. That
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question opens into the broader scientific puzzle of hadalendomism. The tendency of deep trench systems to produce life that exists nowhere else.
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Hadalendemism is one of those concepts that sounds technical at first, but becomes genuinely striking once you understand what it actually means. The word endemism simply refers to species that are found in one specific place and nowhere else. Island endemism is
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familiar enough. the Darwin finches of the Galapagus, the lemurs of Madagascar, creatures that evolved in geographic isolation and became something that the rest of the world does not have. Had endemism works on the same principle, but the islands in question are not
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patches of land surrounded by ocean. They are patches of extreme depth surrounded by shallower seafloor. That is for the organisms living at 8,000 m just as impossible as open water is to a land animal. The reason for this is
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pressure. Life in the hadal zone is not simply life that tolerates pressure. It is life that has been rebuilt at the cellular and biochemical level to function under conditions that would kill anything adapted to shallower water. Cell membranes, enzyme
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structures, the basic machinery of metabolism, all of these have to work differently at 800 atmospheres than they do at one. The adaptations required to survive at Hadal depth are not minor adjustments. They are fundamental reorganizations of how biology operates.
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And those reorganizations take millions of years of evolutionary pressure to produce. Once a lineage has made those changes, it cannot simply migrate across abyssal plains at 3 or 4,000 m and colonize a new trench. The intermediate depths are in a real physiological sense
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hostile to hadal organisms. The pressure is too low. The temperature and chemistry are wrong. The food supply is different. A creature that has evolved to thrive at 8,000 m is in important ways a prisoner of its depth. This is
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why studied Hadal system show such high rates of endemism. Work done in the Kerdc Trench which reaches about 10,000 m in the southwestern Pacific found that a substantial proportion of the amphipod species collected there were not found in the Mariana Trench. Despite the fact
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that the Mariana is only a few thousand km away in geological terms and contains what appears to be a similar environment, the species doing the same ecological job in each trench, scavenging organic material from the sediment, processing marine snow, occupying the top of the
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local food web in terms of mobile invertebrates are different species. They look similar in some ways. They occupy similar niches, but they are genetically and morphologically distinct. the products of long isolation in separate deep systems. Snail fish are
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perhaps the most striking example of this pattern. The family lipid day has produced hadal adapted species independently in multiple trench systems. A process biologists call convergent evolution. In the Mariana Trench, the dominant hadal snail fish is pseudo lipus sware, which was formerly
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described only in 2017 and has been filmed at depths exceeding 8,000 m. In the Atakama trench in the eastern Pacific, a different species, Paraliparis Selti, occupies a similar role. In the Japan trench, yet another distinct snailish lineage has been
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documented. These fish are related, all members of the same broad family, but they are not the same species. Each trench system has over millions of years produced its own version of the deep adapted snail fish shaped by the
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specific conditions of that particular environment. If there is a lipid lineage in the Diamantina deep and the presence of the family in the broader Indian Ocean makes this genuinely plausible, it would almost certainly be distinct from the snail fish found in any Pacific
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trench or in the Java trench to the north. It would be its own thing shaped by the Indian Ocean's particular chemistry and the Diamantina's geological character. Amphipods tell a similar story. Here on Delaya Gigas is the iconic Hadal amphipod of the Marana
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Trench, a crustation roughly 3 cm long that has been found in extraordinary densities near bait deployments at full ocean depth. It is a highly specialized organism with biochemical adaptations including the production of specific enzymes that stabilize cell membranes
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under extreme pressure. But herea gigas is not the only hadal amphipod. Not even close. The genus Honda alone contains multiple species found in different trench systems. And the broader community of hadal amphipods includes representatives from several other genera.
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In the kerdc trench researchers have identified amphipod species that do not appear in the Mariana and vice versa.
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The pattern is consistent. Isolation produces divergence. and divergence produces endemism. What makes the diamantina particularly interesting in this context is the degree of its isolation and the age of that isolation. The diamantina fracture zone formed as the Indoian plate moved
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northward pulling apart from the Antarctic plate along a transformed fault system. This process began tens of millions of years ago and the deep depression that became the Diamantina has been geologically present in some form for a very long time. The seafloor
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in the region is old oceanic crust somewhere around 80 to 100 million years old though the fracture zone itself reached something like its current configuration more recently than that.
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The point is that the diamantina has been a deep isolated system for long enough that whatever colonized it in the early stages of its formation has had an enormous amount of time to evolve in isolation. Tens of millions of years of
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separation from Pacific had systems separated by mid ocean ridges and the particular circulation patterns of the Indian Ocean is more than enough time to produce species that are found nowhere else on Earth. So what might actually be down there? This is the kind of question
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where it is important to be honest about the difference between informed speculation and actual knowledge because we genuinely do not know. But informed speculation grounded in what has been found in analogous systems is not nothing. It is a way of understanding
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what the scientific stakes of exploration actually are. Giant amphipods are a reasonable expectation. The term giant is relative in the deep sea where the word gets applied to organisms that would be merely large by surface standards. But in hadal zones,
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amphipods have been documented reaching lengths of 30 cm or more. A phenomenon sometimes called deep sea gigantism that is thought to result from cold temperatures, high pressure, and the particular metabolic conditions of the had environment.
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Lissianasoid amphipods, the broad group that includes the Hadal scavengers found in multiple trench systems, would be plausible inhabitants of the diamantina.
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Whether they would be the same species as those found elsewhere, a related but distinct species or something genuinely unusual in terms of body plan or behavior is impossible to say without looking. Holyurans, the sea cucumbers are another strong candidate. These
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softbodied dinoderms have been found in virtually every huddle system that has been sampled with cameras or landers.
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They are remarkably successful at depth, moving slowly across the sediment surface and processing organic material through their digestive systems. In some hadal environments, holyans make up the majority of the visible macroal biomass on the seafloor. Different trench systems have different holyan
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assemblages and some species are known only from single trench systems. The diamantina with its salicious ooze and clay sediments and sufficient marine snow input from the productive waters above would be a plausible environment for holyan communities. Whether those
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communities would include species already described from elsewhere or species entirely new to science is one of the open questions. Policate worms are perhaps less dramatic to think about than fish or crustations, but they are biologically important and consistently
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interesting when sampled from hadal depths. These segmented marine worms occupy a wide range of ecological roles in deep sea communities, including predation, deposit feeding, and tube building. Had polyets from different trench systems have shown high rates of endemism in the limited studies that
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have been done. Some are free living moving through the sediment. Others construct tubes anchored to hard substrate.
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The fracture zone walls of the Diamantina with their exposed rock surfaces and complex topography might support polyat communities that look quite different from those on the flat sediment of the deepest floor. There's also the question of foraminifera, the single-sellled organisms with shells
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that have been found in sediment cores from the Diamantina region. Forominaphera are not charismatic in the way fish or crustaceians are but they are biologically significant and scientifically valuable. Some hadal foraminaphera particularly the xenophores are among the largest
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single-sellled organisms known. Siringamina fragilissima a zenaphor found in the Atlantic can reach diameters of nearly 20 cm.
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Xenophire for have been photographed in the Mariana trench and in other deep systems. They aggregate sediment particles into elaborate structures and create microhabitats used by other small organisms.
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Whether xenopheres or related giant ferominifera are present in the diamantina is unknown, but the sediment type and depth are consistent with their presence elsewhere. And then there is the possibility of fish. This is perhaps the most attention-grabbing category for
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understandable reasons because fish are large enough and familiar enough that the idea of an undescribed fish species in the Indian Ocean Adal zone feels genuinely remarkable. But the precedent is there. Pseudoliperous swir the Mariana snailfish was not formally
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described until 2017. Despite the fact that the Mariana Trench has been studied since the 1950s, the hadal snailfish found in the Atakama Trench was described only in 2023.
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These are not obscure microorganisms. They are fish visible to cameras large enough to be noticed and they were still unknown to science until very recently because the expeditions needed to find them simply had not been undertaken at sufficient frequency or depth. The
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Indian Ocean Hadal zone is even less studied than those Pacific systems. If the Diamantina harbors a lipid fish adapted to its specific depth and chemistry, that fish has had no opportunity to be discovered because no camera has been there to see it. What
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makes this particularly interesting from a biological standpoint is not just the novelty of new species for their own sake. Though that is genuinely valuable for the global catalog of biodiversity.
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It is what those species would tell us about the mechanisms of deep sea evolution.
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Every new hadal species that is described and studied adds a data point to the picture of how life adapts to extreme pressure. how biochemical systems are reorganized to function at depth and how populations diverge when separated by geological barriers over
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geological time scales. The Diamantina isolated in the Indian Ocean, geologically distinct from Pacific trench systems and separated from even the better studied Indian Ocean Adal sites like the Java Trench by significant distance and different water mass characteristics represents a
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potentially independent experiment in Hadal evolution. What life did in the Diamantina given its particular set of conditions and its particular history of isolation might look different in important ways from what life did in the Marana or the Kerdc or the Atakarma.
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And those differences if they exist and if they can be documented would be scientifically meaningful.
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The principle at work here is alipatric speciation. the process by which populations of the same ancestral species, separated by a geographic barrier, diverge over time into distinct species because they are no longer interbreeding and because the selective pressures in their separate environments
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push them in different directions. In the deep sea, the barriers are not mountain ranges or rivers. their mid ocean ridges, differences in water mass chemistry, and the physiological impossibility of crossing intermediate depths. The Diamantina sits on one side
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of those barriers, separated from Pacific had systems by the entire width of Australia and the eastern Indian Ocean ridge systems and separated from the northern Indian Ocean Hadell sites by distance and by the particular circulation patterns that govern deep
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water movement in the region. Whatever colonized the Diamantina in the deep past has been in the relevant biological sense alone there ever since. The longer a system has been isolated, the more divergent its life becomes. This is one
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of the clearest patterns in evolutionary biology. Visible in islands, in mountain lakes, in cave systems, and in deep sea trenches, the Diamantina has been isolated for a very long time. The divergence that time allows for is the scientific prize waiting at the bottom
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of 8,047 m of dark water. And it is a prize that cannot be collected by inference or analogy. It can only be collected by going there, dropping equipment to the floor, and looking at what comes back.
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The science of hadal endemism built on the evidence from trenches that have actually been explored makes a strong case that the diamantina contains something genuinely its own. Something that evolved in that specific dark, cold, pressurized environment and nowhere else. Which brings the question
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naturally around to the practical reality of why that has not happened yet and what it would actually take to change it. The answer when you sit with it for a moment is not a dramatic one.
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There is no single reason the Diamantina deep has gone unstudied for so long. No political dispute, no failed expedition, no tragedy that closed off access. The explanation is quieter and in some ways more frustrating than any of those
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things. It is a combination of distance, cost, competing priorities, and the chronic reality that deep sea biology has always had to make its case in a world where scientific funding is finite and the ocean is very, very large. Start
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with the geography because it shapes everything else. The Diamantina Deep sits roughly 1,100 km southwest of Perth, which is itself one of the most isolated major cities on Earth. Perth is not a hub in the way that Tokyo or San Diego or Southampton
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are hubs. Cities with long histories of deep sea research infrastructure, permanent oceanographic institutions, and fleets of specialized vessels within easy reach. Western Australia has a research capacity and Casiro has conducted important work in Australian waters over the decades. But the
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southeastern Indian Ocean is a long way from anywhere, even by the standards of oceanography, which is already a field accustomed to working in remote places.
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A research vessel leaving Perth to work at the Diamantina Deep would need roughly 3 to 4 days of transit just to reach the site, depending on the vessel's speed and the sea conditions, which in that part of the Indian Ocean
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can be genuinely unpleasant. The southern Indian Ocean is not a calm place. It sits at latitudes where the westerly winds, the same winds that made the old sailing routes around the Cape of Good Hope so feared, run almost
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without interruption around the globe. Swells in that region can exceed 4 m on a routine basis during the Southern Ocean's more energetic periods. And even outside the worst months, the conditions are not what anyone would describe as comfortable for precision scientific
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work. Deploying a Hadal lander, a piece of equipment that needs to be carefully lowered over the side of a ship, tracked acoustically as it falls through 8 km of water and then recovered when it releases and floats back to the surface,
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is a delicate operation under ideal conditions. In 4 m swells, it becomes considerably more complicated. The transit time matters financially as well. Research vessels are expensive to operate. A modern oceanographic ship costs somewhere in the range of 20 to
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$40,000 per day when you account for fuel, crew, maintenance, port fees, and the cost of the science team. A dedicated Hadal expedition to the Diamantina, including transit, on-site operations, and return would realistically occupy 3 to 4 weeks of
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ship time. Before a single lander has been built or a single scientist has been paid, you're already looking at a significant portion of a typical research grant budget just to move the ship there and back. This is not unique
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to the Diamantina. It is the arithmetic of oceanography in remote locations. But it does mean that any expedition proposal has to make a very strong scientific case. Not just that the Diamantina is interesting in principle, but that it is more worth the money than
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the other places that are also interesting and perhaps more accessible. The lander equipment itself adds another layer of cost. A freefall Hadal lander capable of operating at 8,000 m is not something you rent from a local supplier. These are specialized
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instruments built to withstand pressures of around 800 atmospheres, equipped with acoustic release systems that allow them to drop their ballast weights and float back to the surface after a program deployment period. They carry bait canisters, highde cameras, sometimes
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sediment corers or water sampling equipment. Building a lander system from scratch costs several hundred,000 at minimum. Institutions that have them, like Newcastle University's Hadal Ecosystem Studies Group, or the teams behind the Five Deeps Expedition, have invested years of engineering work and
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significant funding into developing that capability. Borrowing or chartering access to that equipment for a single expedition is possible, but it adds logistical complexity and cost to an already expensive undertaking. When you add it all together, a focused Hadal
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biological expedition to the Diamantina deep, done properly with multiple lander deployments at different depths within the fracture zone, water column sampling, sediment cing, and enough time on site to actually collect meaningful data would likely cost somewhere between 1 and 3 million US.
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That is not an astronomical sum by the standards of say space exploration or particle physics. But in the world of marine biology and deep sea research, it is substantial. It is the kind of money that requires a dedicated funding
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source, a committed institutional partner, and a proposal that can convince a funding body that the Diamantina is the right place to spend it. And this is where the question of scientific priority becomes relevant.
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The global community of Hadal researchers is not large. There are perhaps a few dozen scientists worldwide who specialize in organisms living below 6,000 m. And the number of active Hadal expeditions in any given year is small.
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Since the year 2000, fewer than 30 expeditions have targeted depths below 7,000 m with biological sampling equipment. Each of those expeditions required years of planning, significant funding, and favorable logistics. The trenches that have received the most attention, the Marana, the Kermadec, the
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Tonga, the Atakama, the Izu Aasawara, are generally the ones that were either historically significant, geographically convenient for major research institutions or the subject of sustained campaigns by well-unded teams. The Mariana Trench has benefited from proximity to research institutions in
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Japan, the United States, and China, all of which have deep sea programs. and the ships to support them. The Kermadec has been studied largely through New Zealand and British expeditions. The Atakama has received attention partly because of its
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unusual chemistry and partly because of its accessibility from South American ports. The Diamantina has none of those advantages. It is far from the major centers of Hadal research. It is not the deepest point in the Indian Ocean, a
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title that belongs to the Java Trench at around 7,290 m, which has received more attention partly for that reason and partly because it is closer to major shipping lanes and research ports in the northern Indian Ocean. The Diamantina is deeper
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than the Java Trench, but it is also more remote and less wellknown outside of specialist circles. In the competition for limited expedition slots and limited funding, it has consistently lost out, not because anyone decided it was unimportant, but because the queue
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is long and the resources are short. There is also a structural issue with how deep sea research funding tends to be allocated. Large international mapping projects like the Nippon Foundation and GEBCO Seabed 2030 initiative which aims to map the entire
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ocean floor to high resolution by 2030 focus primarily on baimetric data meaning the shape and depth of the seafloor rather than biological sampling.
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Seabed 2030 has identified the Diamantina region as one of the least mapped deep zones in any ocean, which is genuinely useful information. Better maps would help future biological expeditions plan their lander deployments more precisely, knowing where the deepest pockets are and what
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the topography of the walls looks like. But mapping and biology are different scientific enterprises funded through different channels. and the existence of a mapping effort does not automatically generate a biological one. The diamantina may eventually get better maps. Whether those maps lead to an
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expedition that actually drops a camera to the floor depends on a separate set of decisions by a separate set of funders. Australia's CSIRO, the Commonwealth Scientific and Industrial Research Organization, has conducted deep sea work in Australian waters over many decades. And some of
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that work has touched on the broader Diamantina fracture zone region. But CSIRO's priorities are necessarily broad. It covers fisheries, climate, mineral resources, coastal management, and a wide range of other scientific domains. And the deeper dal biology of a
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remote fracture zone is one small item on a very long list. The institution has the scientific expertise and the ship capacity to mount such an expedition, but it would require targeted funding and a specific programmatic commitment that has not materialized for the
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dearantina specifically. It is worth being clear about what this situation is not. It is not negligence.
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It is not a failure of scientific imagination. The researchers who work in hadal biology are well aware that the Diamantina deep is unstudied. They know it is likely to contain unique species.
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The scientific case is not in dispute among the people who understand the field. The gap is between the scientific case and the practical reality of getting an expedition funded, equipped, and deployed to a location that requires weeks of ship time and specialized
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equipment that most institutions do not have sitting in a warehouse waiting to be used. Deep sea biology as a field is chronically underfunded relative to its scientific importance. The ocean covers 71% of Earth's surface. The Hadal zone alone, depth below 6,000 m, covers an
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area larger than the entire surface of Europe. The number of scientists, ships, and dollars dedicated to understanding that environment is genuinely small.
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There is something quietly sobering about that proportion. We live on a planet that is mostly ocean and the deepest parts of that ocean, the parts most likely to contain organisms found nowhere else on Earth are the parts we
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understand least and invest in least. The Diamantina is one example of this, but it is far from the only one. The OP trench, the Vimma trench, the horizon deep in the Tonga system, the Puerto Rico trench in the Atlantic, all have
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received only fragmentaryary biological attention. The Diamantina stands out partly because of its depth and partly because its geological distinctiveness makes the case for unique biology particularly strong. But it sits within a broader pattern of underexploration that applies to much of the Hadal world.
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None of this means the situation is static. Had research has expanded significantly over the past 15 years.
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The five deeps expedition between 2018 and 2019 demonstrated that a privately funded initiative could reach the deepest points of all five oceans within a single campaign using a full ocean depth crude submersible and a purpose-built support vessel. That
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expedition visited the Java Trench as the Indian Ocean's representative site, not the Diamantina, but it showed what is possible when the resources and the will are aligned. The development of cheaper, more deployable lander systems by university research groups has
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lowered the barrier to entry for Hadal biological work, at least somewhat. Environmental DNA sampling, which involves filtering water at depth to collect genetic material shed by organisms in the water column, offers a way to detect species presence without
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physical capture. And EDNA methods are becoming more practical for deep sea applications. These developments mean that a dearantina expedition, when it eventually happens, will have better tools available to it than the expeditions of the 1970s and 1980s that
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sampled only the shallower margins of the fracture zone. The logistical challenges are real, but they are not insurmountable. They are the kind of challenges that have been overcome in other remote locations when the scientific motivation was strong enough
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and the funding was found. The dear Mantina is waiting in the most literal sense for someone to decide it is worth the effort. And the scientific evidence drawn from the analogous hadal systems around the world suggests that when that
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decision is finally made, the return on the investment is likely to be significant. But the technology that would actually make it happen and what a well equipped modern expedition to the Diamantina would actually look like in practice is
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worth thinking about carefully because the tools available now are genuinely different from anything that existed when the deep was first measured. So let us think about what that technology actually looks like in concrete terms because it is easy to say that the tools
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exist without explaining what they are or how they work. The image most people carry of deep sea exploration is probably something like a crude submersible. A small pressurized sphere with port holes descending slowly through the dark with a pair of lights
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illuminating a narrow cone of water ahead of it. That image is not wrong, but it is only one piece of a much larger toolkit. And for a place like the Diamantina Deep, the crude submersible is actually not the first instrument you
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would reach for. The workhorse of modern Hadal biological research is the freef fall lander. It is a deceptively simple device and concept though sophisticated in execution. The basic idea is this.
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You build a frame typically made from syntactic foam and aluminum that is negatively buoyant when loaded with weights. You attach your scientific instruments to it. Bait cameras, sediment corers, water samplers, hydrophones, whatever the mission requires. You drop it over the side of
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the ship and it sinks. It sinks freely without a cable, which is what makes it practical at extreme depths. A cable long enough to reach 8,000 m would weigh more than the lander itself and would create enormous drag and handling
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problems. The freef fall approach sidesteps all of that. The lander descends at roughly 1 m/s, which means it takes somewhere between 2 and 3 hours to reach the floor of the diamantina deep from the surface. It sits there for
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a predetermined period, which might be anywhere from a few hours to a full day, collecting data and footage and samples.
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Then an acoustic signal is sent from the ship, a specific frequency that triggers a release mechanism on the lander. The ballast weights drop away and the now positively buoyant frame rises back to the surface on its own. The ship tracks
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it by acoustic pinger and retrieves it when it surfaces. That is the core system. The variations are in what you attach to it. A bait camera lander does exactly what it sounds like. It carries a camera pointed to bait canister,
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usually filled with mackerel or similar oily fish, and records whatever comes to investigate. In wellstudi hadal systems, the footage from these cameras has been extraordinary.
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In the Mariana trench, bait cameras recorded Honda Giga's amphipods, arriving in enormous numbers within minutes of the bait reaching the floor, swarming it in dense clouds that look almost like a living fog. In the Kerdc Trench, snailfish were recorded at
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depths exceeding 7,000 meters, moving with an unhurried, almost leisurely grace through water that would crush an unprotected human body in an instant.
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In the Tonga Trench, a new species of snail fish was recorded in 2023 at 8,336 m, which currently stands as the deepest fish observation ever made. All of that footage came from freeful bait camera systems. None of it required a crude
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submersible. None of it required a cable reaching to the floor. It required a ship, a lander, an acoustic release, and someone willing to deploy the equipment and wait. The Newcastle University Hadal Ecosystem Studies Program known as Hades has been one of the leading groups
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developing and deploying these land systems over the past two decades. Their work in the Pacific has produced some of the most detailed biological data sets ever collected from Hadal depths and their lander designs have been refined through dozens of deployments in some of
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the most hostile environments on the planet. The equipment is proven. The methodology is established. the scientific protocols for processing samples, sequencing DNA from collected organisms, identifying species from video footage, and analyzing sediment cores are all well-developed. What the
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Hades program and groups like it have demonstrated is that systematic Hadal biological work is genuinely possible with the right equipment and the right ship support, even in remote locations.
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The Five Deeps expedition, which ran from 2018 into 2019, was a different kind of operation. It was privately funded by the American explorer and businessman Victor Vesco, and its goal was to reach the deepest point of each of the world's five oceans in a crude
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submersible. The vessel used was the DSV limiting factor built by Triton submarines and it was designed from the outset to withstand full ocean depth pressure, meaning it could theoretically descend to any point in any ocean on Earth. The pressure hole was a titanium
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sphere 90 mm thick, housing a pilot and one observer with a suite of external cameras, lights, and sampling tools. The support ship DSSV Pressure Drop carried the submersible and also deployed lander systems ahead of each crude dive to
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survey the target area and confirm the location of the deepest point. When the Five Deeps team reached the Indian Ocean in 2019, the site they targeted was the Java Trench, which is the deepest point in the Indian Ocean at approximately
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7,290 m. The Java Trench is a subduction trench located south of the Indonesian archipelago. Geologically very different from the Diamantina, but it was the Indian Ocean's deepest confirmed point at the time, and it was the logical target for a record focused
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expedition. During the Java Trench dives, the team observed snail fish at approximately 7,192 m, collected amphipod samples using the lander system, and photographed holothurans moving across the sediment floor. The footage was striking, partly for what it showed, and partly for how
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ordinary some of it looked. A fish moving slowly across a pale sediment plane, a sea cucumber trailing itself across the bottom, amphipods scavenging in the dark.
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life doing what life does at a depth that would have seemed completely uninhabitable to biologists a century ago. The Diamantina deep at 8,047 m is deeper than the Java Trench by roughly 750 m. That difference matters biologically because pressure increases
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with depth and the organisms that survive at 8,000 m are operating under conditions even more extreme than those at 7,000 m. But it does not make the Diamantina inaccessible to the same technology. The DSV limiting factor was rated for full ocean depth. The lander
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systems used by Hades and similar programs have been deployed to depths exceeding 10,000 m in the Mariana Trench. The equipment can reach the floor of the Diamantina. The question has never been whether the technology is capable. It is whether the technology
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gets pointed in that direction. One of the most promising developments in Hadal research over the past decade is environmental DNA sampling or edna.
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The principle is straightforward. Every living organism sheds biological material into the water around it. Skin cells, mucus, feces, fragments of tissue. All of these contain DNA. And that DNA persists in the water column for a period of time before degrading.
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If you filter a large volume of water at depth and then sequence the DNA collected on the filter, you can identify which organisms were present in that water, even if you never saw them, never captured them, never photographed
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them. The technique has been used successfully in freshwater ecosystems for years, detecting rare fish species in lakes and rivers from water samples alone. Its application to deep sea environments is more recent and more technically demanding because the volumes of water needed are larger, the
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DNA concentrations are lower, and the equipment has to withstand extreme pressure while collecting the sample.
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But the methodology is advancing quickly. A well-designed EDNA sampling package deployed on a lander to the floor of the Diamantina could in principle return a genetic snapshot of the biological community present there, including organisms that never approached the bait camera and were
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never captured in a net. The implications of that are significant. One of the persistent limitations of bait camera surveys is that they are selective. They show you the organisms that are attracted to bait, which in hadal systems tends to mean amphopods
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and scavenging fish. Organisms that are not scavengers, holtherans grazing on sediment, polycate worms living in the substrate, microbial communities coating mineral surfaces do not necessarily appear in bait camera footage at all.
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Sediment cores capture some of these organisms, but cores are small and the extraction process can damage delicate fauna. Edna sampling offers a way to get a broader picture of what is present. A kind of biological census of the water
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column, a near bottom environment that does not depend on any particular organism choosing to swim toward a piece of mackerel. For a place like the Diamantina where we have essentially no baseline biological data at all, an Edna survey would be an extraordinarily
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valuable first step. Autonomous underwater vehicles or AUVs add another layer of capability. These are untethered robotic vehicles that follow pre-programmed missions, diving to depth, collecting data, and returning to the surface on their own.
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They are primarily used for mapping and water column surveys rather than biological sampling. But their ability to cover large areas systematically makes them useful for understanding the physical environment of a place like the Diamantina fracture zone, which is not a
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simple bowl, but a complex elongated depression with varied topography. An AUV survey of the fracture zone could identify the precise location of the deepest sections, map the slope angles of the walls, and measure water column properties like temperature, salinity,
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oxygen concentration, and turbidity at multiple depths and positions. That kind of environmental mapping is the foundation on which biological sampling decisions are made. You want to know where to put the lander, and a good AUV survey tells you that. Putting all of
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this together, a realistic modern expedition to the Diamantina Deep would probably look something like this. A research vessel of sufficient size to carry lander systems and potentially an AUV would transit from Fremantle, the port closest to the site, spending
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roughly 4 to 5 days reaching the target area. An initial AUV survey of the fracture zone would be conducted to refine the baimetric picture and identify the deepest accessible points.
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Multiple lander deployments would follow, each targeting different depths within the fracture zone from the abyssal margins down to the deeper sections near 8,000 m. Each lander deployment would carry bait cameras running continuously during the bottom time. Sediment corers to capture the top
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layers of sediment and the organisms living in them. Water samplers to collect water at multiple depths for Edna analysis and possibly hydrophones to record any acoustic activity in the deep environment. The total time on site might be 10 to 14 days, allowing for
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multiple deployments at each target depth and some redundancy in case of equipment issues. The cost of such an expedition, including ship charter, equipment, personnel, and post expedition sample analysis, would likely fall somewhere between 1 and 3 million US, depending on the vessel used and the
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scope of the biological program. That is not a trivial sum, but it is within the range that has been achieved by university consortia, national science agencies, and private foundations for other Dale expeditions.
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The five deeps expedition cost considerably more partly because of the crude submersible and the purpose-built support ship. A lander focused biological survey of the Diamantina would not require that level of infrastructure. It would require a capable research vessel, proven lander
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systems, a small team of Hadal biologists and technicians, and the logistical will to get to a remote location in the southeastern Indian Ocean and spend 2 weeks working there.
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The scientific case for doing it is not subtle. Every wellstudied Hadal system that has been examined with modern biological tools has produced new species. The KerdC trench surveys of the past decade have described new amphipods, new polyates, new holyan
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species. The Mariana Trench continues to yield new microbial strains with each new sampling campaign.
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The Java trench visited seriously for the first time in 2019 immediately produced snailfish observations and amphipod collections that added to the Indian Ocean hadal biological record.
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The Diamantina deep is deeper than the Java trench. Geologically distinct from any Pacific had system and has been isolated in the Indian Ocean for tens of millions of years. The probability that it contains organisms not found anywhere else is not a speculative hope. It is a
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straightforward inference from everything we know about how Hadal biodiversity works. There is also a practical dimension to new Hadal species that goes beyond pure taxonomy.
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Pophilic bacteria, organisms that require high pressure to function, have already attracted significant interest from biotechnology researchers because the enzymes they produce are stable under conditions that would denature ordinary proteins.
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Pressure stable diodoir polymerases, for instance, have potential applications in industrial biochemistry. Novel microbial strains from unstudied hadal systems represent a largely untapped library of biochemical novelty.
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And the diamantina's distinct geological and chemical environment makes it plausible that its microbial communities would differ meaningfully from those already sampled in Pacific trenches.
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That is not the primary reason to study the deep, but it is a real dimension of the scientific value. What is perhaps most striking when you lay all of this out is how achievable it is. The Diamantina Deep is not waiting for some
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future technology that has not been invented yet. It is not waiting for a breakthrough in material science or propulsion or robotics. The instruments that could reach its floor and return biological data to the surface already exist. They have been used in other
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oceans. They have worked. The gap between what we know about the dear mantina and what we could know is not a gap in capability.
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It is a gap in attention and resources which is a different kind of problem and in some ways a more frustrating one because it does not have a technical solution. It has a funding solution. It has a prioritization solution. The
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microbial world of the Diamantina Deep is perhaps the most overlooked dimension of this story, and it deserves its own careful attention. Because even if the larger animals remain unseen for years to come, the microbial life at the floor
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of the deep is almost certainly extraordinary in ways that we're only beginning to understand in other Hadal systems. So let us stay down there for a moment in the sediment in the dark and think about what microbial life in a
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place like the Diamantina deep might actually look like. This is not a small question. It is easy to think of microbes as background noise as the invisible layer that exists beneath the more legible world of fish and crustations and squid. But in hadal
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environments, the microbial community is not background. It is the foundation. It is often the majority of the biomass.
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And in places that have never been sampled, the microbial world is the most certain source of genuine novelty because it is both the most abundant and the least explored.
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What we know about Hadal microbiology comes primarily from the Mariana Trench with additional data from the Kerdc, Tonga, and Japan trenches and a handful of other sites in the Pacific.
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The picture that has emerged over the past two decades is genuinely surprising even to researchers who expected to find life in these places. One of the more counterintuitive findings is that microbial cell densities in Hadal sediments tend to be substantially
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higher than in the surrounding abyssal planes at similar depths. In the Mariana trench, studies published in the early 2010s found that sediment samples from the trench floor contained microbial cell counts up to 10 times higher than sediment samples from the flatter
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abyssal plane surrounding the trench at comparable depths. The reason for this is partly geometric. Trenches and deep fracture zones act as funnels. Organic matter, the constant slow rain of dead plankton, feal pellets, and decaying organisms sinking from the sunlit
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surface tends to concentrate in depressions in the seafloor. The sloping walls of a trench or fracture zone channel this material downward toward the deepest points where it accumulates in the sediment. The deep floor of the dear mantina fracture zone with its
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elongated riftlike depression and steep internal walls would function in exactly this way. Organic material settling from the productive surface waters above would be funneled progressively deeper, concentrating in the sediment at the bottom of the deepest sections.
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That concentrated organic input is food, and microbes are extraordinarily good at exploiting it. The organisms doing this exploiting are not ordinary bacteria.
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The pressure at 8,000 m, approximately 800 atmospheres, is lethal to almost every organism evolved for surface conditions. Proteins denature, membranes lose their flexibility, cellular machinery seizes. The bacteria that thrive in hadal sediments are popiles, a word derived from the Greek for
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pressure. These are organisms that do not merely tolerate high pressure, but actually require it. Many pestphilic bacteria isolated from hadal sediments grow poorly or not at all at surface pressures. They have evolved membrane lipid compositions that remain fluid
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under conditions that would turn ordinary bacterial membranes rigid and nonfunctional. Their enzymes are shaped to work under pressure and in some cases pressure actually enhances their enzyatic activity rather than inhibiting it.
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One of the most studied pophilic bacteria is shaanella. First isolated from sediments in the Marina trench at depths around 10,000 m.
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It has since been found at various hadal sites and has become something of a model organism for understanding how bacteria adapt to extreme pressure. Its genome encodes a range of pressure adaptive features, including specific fatty acid synthesis pathways that
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produce the highly unsaturated lipids needed for membrane fluidity at depth. Studying Shuanella Bentha and its relatives has given researchers a clearer picture of the molecular toolkit required for life at Hadal pressure. And it has also raised the obvious question
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of how much variation exists across different Hadal systems. Because shanella benthica is not the only psophile in the Mariana. It coexists with dozens of other bacterial taxa many of them poorly characterized and the community composition of hadal microbial assemblages varies
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significantly between trenches. The Kerdc trench has a different microbial community from the Marana. The Japan trench has a different community.
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Again, each system has been shaped by its own geological history, its own sediment chemistry, its own organic input from the surface waters above it, and its own isolated evolutionary trajectory. The Diamondina fracture zone sits in the eastern Indian Ocean beneath
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waters that have their own distinct biological productivity patterns, their own seasonal dynamics, and their own organic export characteristics.
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The sediment that has been accumulating on the floor of the Diamantina deep for the past tens of millions of years reflects all of that. Based on the limited sediment data available from the broader region, the deep floor of the
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Diamantina is likely covered primarily in cicius ooze. The fine grained sediment composed largely of the silica skeletons of datoms and radolarans that once lived in the surface waters above.
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Mixed into this would be clay minerals and the remains of other planktonic organisms. This sediment type supports a particular kind of microbial community, one adapted to processing the organic compounds preserved within the ooze. And the specific chemistry of the Indian
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Ocean's deep water with its lower oxygen concentrations compared to equivalent Pacific depths would further shape which microbial metabolic strategies are most successful.
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Oxygen is a critical variable in deep sea microbiology. In well oxygenated hadal sediments, aerobic bacteria dominate using dissolved oxygen to break down organic matter in the most energetically efficient way. But when oxygen is scarce, which it is in parts of the
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Indian Ocean deep due to the particular circulation patterns of that ocean basin, other metabolic strategies come to the four. Anorobic bacteria, organisms that use sulfate, nitrate, iron, or manganese as electron acceptors instead of oxygen, become more important. These different metabolic
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communities produce different chemical byproducts, create different sediment chemistry, and leave different signatures in the geological record.
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The Diamantina's relatively low deep water oxygen levels suggest that its sediment microbial community might include a significant anorobic component which would be distinct from what has been found in better oxygenated Pacific hadal sediments. Then there is the question of the fracture zone walls
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themselves. The diamantina fracture zone is not a simple flat bottom depression. It is a tectonically complex structure with steep walls, exposed rock faces, and varied mineral surfaces.
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Old oceanic crust, the kind that forms the basement of the Diamantina region, contains minerals, including iron and manganese compounds, sulfides, and silicut. Some bacteria are chemolytroofs meaning they derive energy not from organic matter but from the chemical oxidation of minerals. These organisms
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can colonize rock surfaces and live entirely independently of the organic rain from above. In hydrothermal vent systems, chemoliththotrophic bacteria form the base of entire food webs that owe nothing to sunlight. The Diamondina Deep does not appear to have active
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hydrothermal venting, but the exposed mineral surfaces of the fracture zone walls could still support communities of chemolithroofs at lower densities living slowly on the chemical energy available in the rock itself. This is speculative to be clear. No one has sampled the
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walls of the Diamantina fracture zone at depth. No one has measured the mineral chemistry of its exposed rock faces. But the geological setting is consistent with the kind of environment where chemoliththotrophic communities have been found elsewhere. And the
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possibility is worth noting because it represents a form of life that would be completely independent of anything happening at the surface. A microbial community living on the walls of the Diamantina fracture zone at 6,000 or 7,000 m eating rock would be living in a
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world that has been sealed off from the surface biosphere for millions of years. its evolutionary history would be its own. There is also the question of viruses which tend to be overlooked in discussions of deep sea life but which
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are extraordinarily abundant in marine sediments. Viruses in hadal sediments have barely been studied at all. What little data exists from the Mariana Trench suggests that viral abundances in Hadal sediments are high and that viruses play an important role in
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controlling bacterial population sizes and driving genetic exchange between microbial lineages through a process called transduction where viruses accidentally carry genetic material from one bacterial cell to another. In isolated environments like Hadal trenches, this kind of horizontal gene transfer can be an important driver of
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microbial evolution, spreading useful adaptations through a community faster than ordinary mutation alone. The viral community of the diamantina deep sediments like almost everything else about that environment is entirely unknown.
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What is known from the broader study of hadal microbiology is that the microbial communities in these environments are not simple. They're not just a few hardy species clinging to existence in extreme conditions. They are diverse, active, and in some cases surprisingly
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productive. Rates of microbial carbon processing in hadal sediments measured in better studied trenches are higher than would be predicted from the organic carbon input alone, suggesting that the concentrated organic matter in the trench funnel is being processed efficiently by a well adapted microbial
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community. These communities are doing real biogeeochemical work, cycling carbon, nitrogen, sulfur, and other elements in ways that connect the Hadal zone to the broader ocean chemistry. The deep is not a dead end. It is a processing zone, and the microbes are
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running it. For the diamantina, all of this means that even if no fish, no crustation, no worm of any describable kind has ever been collected from its deepest sections, the sediment on its floor almost certainly contains a rich
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and unique microbial world. Unique because the Indian Ocean deep has a different chemistry from the Pacific.
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unique because the Diamantina's geological setting, its sediment type, its organic input, and its water column oxygen profile differ from those of every other hadal system that has been sampled. Unique because isolation over geological time scales produces divergence, and the microbial lineages
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in the Diamantina sediments have had tens of millions of years to evolve in their own direction without any connection to the microbial communities in Pacific trenches. And this uniqueness has practical dimensions that extend well beyond pure science. Pzophilic
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bacteria produce enzymes that are stable under conditions of high pressure and low temperature. These enzymes are structurally different from their surface world counterparts in ways that make them interesting to biotechnology researchers.
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Pressurestable DNA polymerases, enzymes that replicate DNA efficiently under high pressure, low temperature conditions, have been explored as tools for molecular biology applications where conventional enzymes perform poorly.
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Protices, lipaces and other industrial enzymes from pzopilic bacteria have attracted interest for applications in food processing, pharmaceutical manufacturing and bioreediation because their stability under extreme conditions can be useful in industrial processes that involve high pressures or low temperatures. Every new hadal system
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that is sampled potentially yields new microbial strains with novel enzyatic properties. And the diamantina with its distinct chemistry and long isolation is a plausible source of microbial novelty that has never been tapped. There is something quietly remarkable about this.
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the floor of the Diamantina deep. A place 8,047 meters below the surface of the Indian Ocean. A place that no human instrument has ever visited in any meaningful biological sense may contain microbes whose enzymes could eventually find applications in medicine or industry.
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That is not a far-fetched claim. It is an extrapolation from things that have already happened in other Hadal systems.
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The gap between that potential and the current reality, which is that the Diamantina's microbial world is completely unstudied is a gap that exists not because the science is too hard, but because no one has yet found the resources and the will to go there
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and look. It is also worth pausing on what it means to study microbes in a place like the Diamantina, even in the absence of a lander or submersible.
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Environmental DNA sampling, the technique of filtering seawater and sediment for fragments of genetic material shed by living organisms, has opened a new avenue for deep sea biological surveys that does not require physically capturing any organism. A water sampler deployed on a standard
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oceanographic wire could in principle collect water from within the diamantina fracture zone at various depths and the edna extracted from those water samples could be sequenced to reveal which microbial tax are present, how abundant they are relative to each other and
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whether they include lineages not found in other hadal systems. This kind of survey would not replace sediment sampling because the organisms actually living in the sediment are different from those suspended in the water column above it. But it would provide a first
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biological fingerprint of the Diamantina environment at a fraction of the cost and complexity of a full lander deployment. The same Edna approach has been used in other deep sea contexts with striking results. Water column EDNA surveys in the Mariner Trench have
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detected microbial taxer at Hadal depths that were not previously known to exist there and have revealed gradients in community composition across different depth layers that match the physical stratification of the water column. A similar survey in the Diamantina, even a
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relatively simple one, would be the first biological data ever collected from that environment, and it would almost certainly reveal something worth knowing.
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The microbial story of the Diamantina Deep is in a sense the most accessible part of a much larger story of ignorance. The large animals, the fish and amphipods and holurans that might live on the floor of the deep require
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sophisticated lander systems to detect. The microbes can be reached at least partially with equipment that is already aboard most oceanographic research vessels. That makes the absence of any microbial data from the Diamantina even more striking. It is not that the tools
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were unavailable. It is that the Diamantina has simply not been on the agenda. But the surrounding Indian Ocean has been studied at least in part and what those studies have found in nearby regions gives some sense of what the
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dear mantina might be hiding in its waters and on its floor. The biological context of the Indian Ocean deep, the species that have been found in the trenches and abyssal plains that surround the Diamantina fracture zone is the next part of this picture and it is
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a context that makes the diamantina's silence feel all the more conspicuous. So let us look at what the surrounding Indian Ocean has actually produced because the scientific record from nearby regions is not empty. It is thin and in places is very old but it exists
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and it tells a story that the Dear Mantina deep sitting at the center of it cannot yet tell for itself. The most significant recent data point comes from the Java Trench, which holds the title of the deepest point in the Indian Ocean
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at approximately 7,290 m located off the southern coast of the Indonesian archipelago. In 2019, the Five Deeps expedition, the same project that sent the submersible DSV limiting factor to the deepest points of all five oceans, made a crude
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descent into the Java Trench. What they found was not nothing. Snailfish were observed and filmed at approximately 7,192 m. Members of the family liperiday, the same broad family that holds the depth record in the Pacific. Amphipods were collected from bait traps deployed on
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the seafloor. Holyurans, those slowmoving sea cucumbers that seem to turn up at almost every hadal depth where anyone has bothered to look, were photographed moving across the sediment.
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The Java trench, despite being shallower than the Diamantina deep by more than 700 m, is biologically alive in ways that are recognizable from other hadal systems. Life adapted to that pressure, that cold, that darkness. It found a way
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in. What makes the Java trench finding particularly relevant to any discussion of the Diamantina is the geographic relationship between the two systems.
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They are both Indian Ocean hadal environments. They share the same broad oceanographic context. The same deep water circulation patterns driven by Antarctic bottom water. The same general temperature range at depth. The same broad category of organic input from the
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surface ocean above. And yet they are separated by a significant distance and by geological structures that would limit or prevent the exchange of bottom dwelling fauna between them. The snail fish observed in the Java Trench are not the same species as whatever snailish
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might exist in the Diamantina, if any do. The amphipods in the Java Trench bait traps are almost certainly not the same species as whatever amphipods might be crawling across the floor of the Diamantina fracture zone. But the fact
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that these organisms exist in one Indian Ocean Hadal system is a reasonable indicator that the Indian Ocean deep as a whole is capable of supporting Hadal life.
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The Diamantina is not in a biologically hostile corner of the world. It is in the same ocean subject to the same broad conditions and it is deeper.
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Going further back in time, there is a body of work from Soviet research vessels that operated extensively in the southern Indian Ocean during the 1950s, 1960s, and 1970s.
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Soviet oceanography during this period was in some respects ahead of Western efforts in terms of geographic coverage.
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Soviet ships reached remote deep sea regions that western vessels had not prioritized and they did biological sampling using trolls and grab samplers at Abyssell and occasionally Hadal depths. The OB trench and the Vimma trench both located in the southern
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Indian Ocean received some of this attention. The results were published in Soviet scientific literature. Some of which was translated into English and some of which was not. And the data has never been fully integrated into modern global Hadal biodiversity databases.
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What the Soviet work in the OB and Vimma trenches found was broadly consistent with what had biology and other systems had shown.
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Amphipod communities dominated the macroal assemblage at the deepest sampling depths. Polyat worms were present in sediment samples and the overall picture was one of low species richness but high individual abundance particularly for the amphopods.
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This is a pattern seen across hadal systems globally. The deep concentrate certain kinds of life especially scavenging crustations that can exploit the organic material accumulating at the bottom while filtering out others. The Soviet samples were not from the
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Diamantina fracture zone specifically and the deepest sampling depths in those trenches were considerably shallower than 8,47 m. But they established that the southern Indian Oceanadal environment is not a biological void.
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There is also the work done by Australian scientists primarily through CSIRO, Australia's National Science Agency in the southeastern Indian Ocean during the 1980s and 1990s.
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These surveys were not focused on hadal depths. They were broad deep sea surveys aimed at characterizing the abyssal fauna of the region and they operated mostly in the depth range of 2,000 to 5,000 m which is abyssal rather than
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hadal. But the species assemblages they documented a relevant background. Rattail fish members of the family macro day were found to be common at these depths throughout the southeastern Indian Ocean including in waters not far from the Diamantina fracture zone. Deep
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sea sharks including species from the family's etmopter terod and somnioid were recorded at abyssal depths. Various echinoderms, crustations and policates rounded out the picture of a moderately diverse abyssal community in waters that are geographically adjacent to the diamantina system. This matters because
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the abyssal fauna of a region and the hadal fauna of a trench within that region are not entirely disconnected.
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The Hadal zone is fed by the same marine snow that sustains the abyssal plane around it and some species ranges extend across the boundary between Abyssal and Hadal depths. Though most Hadal specialists are confined to the deep, the abyssal communities documented by
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CSIRO surveys in the southeastern Indian Ocean represent the biological world from which Hadal species in the Diamantina fracture zone would have originally derived millions of years ago before the long process of Hadal specialization began. Understanding what lives at 3,000 or 4,000 meters in the
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waters above the Diamantina gives at least a rough sense of the ancestral stock from which whatever lives at 8,000 m might have descended.
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And there is one more piece of context that is easy to overlook. The waters above the Diamantina deep, the sunlit surface ocean and the meopelagic and baopalagic zones above the fracture zone are not biologically empty.
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The southeastern Indian Ocean supports populations of blue whales, the largest animals on Earth, which feed on krill in productive surface waters not far from the Diamantina region. Sperm whales are known to range through these waters as well. And sperm whales are relevant to
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the deep in a very specific way. They dive to extraordinary depths, routinely reaching 1,000 m and in some documented cases exceeding 2,000 m, hunting squid in the deep water column. Their presence in the waters above the Dantina fracture
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zone means that the water column is productive enough, rich enough in prey to support large apex predators, that productivity cascades downward. The organic material produced in the surface ocean, the bodies of phytolanton and zup plankton, the fecal pellets of krill and
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fish, the carcasses of larger animals. All of this sinks and a portion of it reaches the floor of the diamantina deep as marine snow, the fundamental energy source for everything that lives down there. Colossal squid, masonicus hamilton have been recorded in the
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southern Indian Ocean. These are not small animals. Specimens recovered from sperm whale stomachs and from research vessel by catch have measured over 4 m in mantle length and their total length including tentacles is estimated to exceed 10 m in mature individuals. They
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are thought to live primarily in the meopelagic and baipelagic zones of the southern ocean and adjacent regions and the southern Indian Ocean falls within their known range. Colossal squid are not hadal animals. They do not live at 8,000 m, but their presence in the
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broader region is a marker of the biological richness of the water column above the Diamantina. And it reinforces the point that the Indian Ocean deep is not a barren system sitting beneath an empty sea. There is something about this
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pattern of surrounding richness that makes the Diamantina's silence feel almost deliberate, though of course it is not. It is simply the result of where research ships have gone and where they have not. Every time a vessel has operated in the Indian Ocean deep with
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appropriate equipment, it has found something. The Java trench yielded snail fish and amphipods. The Auburn Vimma trenches yielded amphipod communities.
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The southeastern Indian Ocean abyssal plane yielded rattail fish and deep sea sharks. The surface waters above the Diamantina support blue whales and colossal squid. The pattern is consistent. Look carefully. Find something. The Diamantina has not been looked at carefully. Not at its deepest
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point. Not with landers or cameras or sediment corers or Edna samplers. The blank in the record is a blank of effort, not a blank of biology.
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It is worth being precise about what is and is not known from the Diamantina region specifically because it is easy to conflate the broader Indian Ocean record with the Diamantina itself. The troll samples collected by Australian vessels in the 1970s and 1980s from the
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Diamantina fracture zone came from the shallower sections of the fracture zone. The walls and ridges at depths of perhaps 2,000 to 4,000 m, not from the deepest basin. The ratel fish and cuskils recovered in those trolls were from the upper margins of the fracture
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zone, not from anywhere near 8,047 m. The sediment cores that showed salicious ooze and foriniferus were from similar depths. None of this material came from the hadal zone of the diamantina.
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None of it tells us what lies at the bottom. This distinction matters because the difference between 4,000 m and 8,000 m is not just a number. It is a biological boundary. The pressure at 8,000 m is roughly double the pressure
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at 4,000 m. The species that live at 4,000 m in the dear mantina fracture zone cannot survive at 8,000 m. The Adal fauna, if it exists, is a separate community adapted to conditions that species in the shallower troll samples
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would find lethal. What we know from the margins of the Diamantina is not a preview of what lives at the bottom. It is a different story entirely. This is one of the things that makes Hadal biology so conceptually interesting and
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also so practically challenging. The Hadal zone is not simply a deeper version of the abyssal plane. It is a distinct environment with its own selective pressures, its own food dynamics, its own community structure.
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The species that have colonized Hadal depths have done so through evolutionary processes that took millions of years and produced organisms that are in some cases physiologically unrecognizable from their abyssal relatives. Hadal amphipods are larger than their shallower relatives, a phenomenon called
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deep sea gigantism that is related to the cold temperatures and high organic input of hadal environments. Hadal snail fish have bodies that are adapted to function at pressures that would destroy the cell membranes of surface fish. The hadal zone produces specialists and
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those specialists are what the diamantina may be hiding. The Indian Ocean context then gives us a frame but not an answer. It tells us that the Indian Ocean deep supports life that had conditions in this ocean are not
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incompatible with the survival of macroa and that every system examined so far has yielded biological findings. It tells us that the water column above the diamantina is biologically productive and supports a rich community of organisms whose organic remains sink to
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the floor below. It tells us that the geological and chemical conditions of the Diamantina are distinct enough from Pacific Hadal systems that whatever lives there is likely to be different from what has been found in the Mariana or the Kerdc. But it does not tell us
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what is actually on the floor of the Diamantina deep cuz no one has looked.
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The surrounding record keeps producing discoveries. New species from the Java Trench, new amphipod records from the southern Indian Ocean, new microbial data from abyssal sediments in the region. Each of these findings adds a piece to the picture of the Indian Ocean deep as a
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living system. The Diamantina sits at the center of that picture, deeper than any of the surrounding data points, and it contributes nothing to the record because nothing has been collected from it. It is the deepest hole in a map that
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is already full of holes and it has remained that way not because the biology is absent but because the expedition has not happened and yet the surrounding world keeps hinting. The snail fish in the Java trench at 7,192
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m suggest that lipid fish can survive at Indian Ocean hadal depths. If they can survive at 7,192 m in the Java Trench, the question of whether a related species might survive at 8,47 m in the Diamantina is not
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unreasonable. Snailfish have been recorded at 8,336 m in the Mariana Trench. So the depth alone is not a barrier in principle. The Indian Ocean chemistry is different from the Pacific and that difference matters for the specific adaptations required.
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But the evolutionary pathway exists. The family leperidi has demonstrated repeatedly and in multiple ocean basins that it can produce hadal specialists.
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The diamantina is a plausible environment for one. The same logic applies to amphipods to polyates to holtherans.
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Every group of organisms that has successfully colonized dal depths and other systems is in principle capable of colonizing the diamantina if the conditions permit. And the conditions based on what we know from analogous systems appear to permit it. The
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temperature is right. The pressure while extreme is within the range that pophilic organisms can handle. The organic input from the productive surface waters above is sufficient to sustain a food web. The geological setting with its complex topography of
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ridges and basins would provide a variety of microhabitats for different species. Everything we know about hadal biology suggests that the Diamantina should be inhabited. The question is by what and in what numbers and with what degree of uniqueness. That question remains open.
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It will remain open until someone builds the expedition, loads the landers, sails the 1,100 km from Perth, and drops a camera to the floor of the Diamantina Deep. Until then, the surrounding record serves as a kind of circumstantial
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evidence, a body of clues that points toward a conclusion without being able to confirm it. The Indian Ocean Deep is alive. The Diamantina is the deepest part of it. The two facts sit next to each other, and the space between them
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is where the real story waits. What makes that waiting particularly interesting is that the surrounding environment is not just biologically rich in the ways that have been documented. There are also stranger, less well understood signals coming from the waters near the Diamantina.
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Signals that suggest the region's biology may be more active and more complex than even the formal scientific record implies. Those stranger signals are worth spending some time with because they sit in an interesting space between the documented and the merely
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reported and the distinction matters. This is not a region of the ocean that generates dramatic headlines or attracts the kind of breathless speculation that some deep sea locations do. The Diamantina Deep is not famous. It is not the subject of folklore or maritime
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legend in the way that certain other stretches of ocean are. What comes from this region is quieter than that and in some ways more interesting precisely because of its quietness. It is not the stuff of monster stories. It is the
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stuff of notes in log books of observations that researchers and mariners recorded without particular fanfare and which have since sat in archives and databases without much attention.
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The southeastern Indian Ocean taken as a whole is one of the more biologically active stretches of open ocean on the planet.
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This surface waters above the Diamantina region are influenced by the subtropical convergence zone where warmer tropical water meets cooler sub Anantarctarctic water producing conditions that support high primary productivity.
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Phytolankton blooms in this zone can be substantial. The food web built on that productivity extends upward through zup plankton, small fish, squid, and then into the large pelagic predators that make this part of the Indian Ocean notable even to non-scientists.
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Blue whales pass through the region on migration routes that are still not fully mapped. The southeastern Indian Ocean supports one of the larger populations of pygmy blue whales, a subspecies that is slightly smaller than the Antarctic blue whale, but still
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among the largest animals on Earth. Sperm whales are present year round in deeper water. And this matters for the story of the dear Mantina. Because sperm whales are not simply surface animals, they are deep divers. The recorded maximum dive depth for a sperm whale is
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just over 2,000 m based on data from depth recording tags. And there is some evidence from stomach contents that they hunt at even greater depth than their tags have confirmed.
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Sperm whales eat colossal squid and colossal squid are not surface animals. The presence of sperm whales hunting actively in the water column above the Diamantina tells you something about the density of prey at depth in this region.
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These are not animals that travel thousands of kilometers to hunt in empty water. Colossal squid themselves are worth a mention here. Mesonicus Hamiltoni, the colossal squid, is the largest invertebrate on Earth by mass, reaching estimated weights of up to 495
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kg. Based on specimens that have been recovered from sperm whale stomachs and from fishing by catch near Antarctica, they are known to inhabit the southern ocean and the deep waters of the sub Antarctic Indian Ocean.
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The southern diamantina region sits at the northern edge of the colossal squids known range. And while no colossal squid has been confirmed from the diamantina fracture zone specifically, the presence of sperm whales actively foraging in these waters suggests that large
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sephalopods are present at depth. This is not a claim that colossal squid live in the diamantina deep itself. The hadal zone at 8,000 m is almost certainly too deep and too cold even for an animal as adapted to pressure as a large squid.
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But it is a reminder that the water column above the deep is not empty. It is layered with life, including very large life, in ways that are not fully cataloged.
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There are also accounts from fishing vessels and research ships operating in the broader region that describe bioluminescent events of unusual scale.
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Bioluminescence in the deep ocean is common. It is in fact the dominant form of light production in the deep meopelagic and baipelagic zones where an estimated 76% of species produce some form of biological light.
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What makes certain accounts from the southeastern Indian Ocean noteworthy is not the presence of bioluminescence but its reported scale and character. Some vessels have recorded what crew members describe as large, diffuse, glowing patches visible from the surface at
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night, extending over areas of hundreds of square meters, appearing and disappearing over the course of hours.
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These events, sometimes called milky seas, are a documented phenomenon in the Indian Ocean, though they are more commonly reported in the northwestern Indian Ocean near the Arabian Sea. The mechanism behind milky seas is thought to involve massive blooms of
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bioluminescent bacteria potentially vibrio harvei which can produce continuous light across enormous surface areas when conditions favor their growth.
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Whether the events reported near the diamantina region are true milky seas or something else is not established. The accounts are anecdotal. They have not been studied with the instruments needed to characterize what was actually producing the light. It is entirely
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possible that what observers saw were dense concentrations of bioluminescent zup plankton or fish schools near the surface rather than bacterial blooms.
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The point is not that these events are mysterious in a supernatural sense. The point is that they reflect the biological richness of the water column in this region. A richness that expresses itself in ways that are sometimes visible even from the deck of
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a ship at night and which hints at the density of life operating across the full depth range of the water column.
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Below the surface in the deep water column, the signals become harder to interpret. The Australian government operates a network of hydro acoustic monitoring stations as part of the comprehensive nuclear test ban treaty organization's international monitoring system. These stations are designed to
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detect the acoustic signatures of nuclear tests, but they are sensitive enough to record a wide range of underwater sounds, including geological activity, ship noise, marine mammal vocalizations, and sounds of uncertain origin. One of the Australian hydro acoustic stations located on Cape Lewin
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in Western Australia is positioned to monitor a broad arc of the eastern Indian Ocean that includes the Diamantina region.
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The hydro acoustic record from the Indian Ocean is not publicly detailed in the way that say Noah's Pacific hydrophone network data sometimes is.
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But researchers who work with underwater acoustics in the Indian Ocean have noted that the southeastern Indian Ocean produces a complex acoustic environment with contributions from geological sources, citation vocalizations, and what are sometimes categorized as unidentified biological sounds. Low
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frequency sounds in the ocean can travel enormous distances, sometimes thousands of kilome, which makes attribution genuinely difficult.
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A sound recorded near Cape Lewan might originate from a blue whale near the Kirgulan Islands, from a geological event along the Southeast Indian ridge, or from something in the water column above the Diamantina.
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Separating these sources requires careful analysis and often multiple recording stations to triangulate the origin.
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What this means in practical terms is that there is no specific mysterious sound that can be pinned to the Diamantina deep and presented as evidence of unknown biology. That would be overclaiming.
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The acoustic environment of the southeastern Indian Ocean is rich and complex and most of what is recorded in it has plausible explanations.
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But the existence of that complexity is itself informative. It tells you that the water column in this region is acoustically active, that large animals are present and producing sounds, and that the biological environment is not quiet or sparse. The deep below all of
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that activity is connected to it. Organic matter from the productive surface and midwater zones sinks continuously to the floor of the Diamantina. The animals in the water column above contribute to that reign of organic material through their feal
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pellets, their mols, their deaths. The deep is not separate from the world above it. It is fed by it. Sperm whales are particularly relevant here because of their relationship with deep topography.
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Research on sperm whale foraging behavior has found that they tend to concentrate their diving activity near underwater ridges, seammounts, and fracture zones. where upwelling currents and topographic complexity create aggregations of prey. The Diamantina fracture zone with its extreme
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topographic relief, its ridges rising thousands of meters above the surrounding seafloor and its deep basins is exactly the kind of geological feature that attracts deep diving citations.
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Acoustic surveys of sperm whale distribution in the Indian Ocean have found that they are not randomly distributed across the open ocean. They cluster near features. The diamondina fracture zone is a feature where the sperm whales regularly hunt directly
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above the deepest parts of the diamantina has not been studied in detail, but the broader pattern of citation behavior in similar geological settings suggests it is plausible. It is worth being clear about what all of this does and does not tell us. None of the
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accounts from fishing vessels, none of the bioluminescent observations, none of the hydro acoustic complexity constitutes evidence of unknown species in the diamantina deep itself. The hadal zone below 6,000 m is a distinct environment from the water column above
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it. What swims at 500 m or 2,000 m in the water column above the diamantina is not the same as what might live on the floor at 8,047 m. The sperm whales are not diving to the bottom. The
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bioluminescent events are surface and near surface phenomena. The acoustic signals are from the water column, not from the sediment floor. So there is a real and important distinction between saying that the region is biologically rich, which it clearly is, and saying
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that the deep floor itself is inhabited by unknown species, which remains an open question. But the richness of the surrounding environment is not irrelevant to that question. It is in fact one of the reasons that had biologists would expect the Diamantina
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floor to be inhabited. The food supply matters. The organic input that reaches the floor of a hadal zone is a function of the biological productivity of the water column above it and the southeastern Indian ocean is productive.
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The funnelike topography of the diamantina's deepest sections would concentrate sinking organic material as happens in other Hadal systems creating a relatively foodrich environment by Hadal standards. The presence of large active animals in the water column above means that larger, more energy richch
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organic packages, whale falls, squid carcasses, fish remains are also reaching the deep floor with some regularity.
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Whale fools in particular are known to support entire communities of specialized organisms on the deep sea floor, including bone eatating worms of the genus oidax, sulfur reducing bacteria, and a succession of scavengers and decomposers that can occupy a single
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whale carcass for decades. Whether whale falls reach the floor of the Diamantina deep at 8,047 m is not known, but sperm whales do die in the open ocean and their carcasses do sink and the diamantina is directly below waters
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where sperm whales are present. There is also the matter of what happens acoustically at the very bottom of deep ocean trenches and depressions.
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Researchers studying the Mariana Trench have found that the trench acts as an acoustic funnel, concentrating sounds from the water column above and from distant sources.
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Low frequency sounds that would dissipate across a flat abyssal plane are instead channeled and amplified within the trench structure. This has implications for the biology of hadal zones because sound is used by many marine animals for communication, navigation, and prey detection.
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Whether the diamantina deep has similar acoustic properties is not known because no one has deployed hydrophones at the bottom of it. But the geometry of the depression, narrow and elongated with steep walls, suggests that it might concentrate sound in ways that could
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influence the sensory environment experienced by organisms living there. This is speculative, but it is the kind of speculation that is grounded in documented physics rather than imagination. What the region around the Diamantina keeps offering then is a picture of a biologically active and
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physically complex environment that surrounds a central unknown. The surface is full of whales and squid and bioluminescent blooms. The midwater column is acoustically complex and inhabited by an unknown but clearly substantial community of meopilagic and baipelagic organisms. The shallower
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margins of the fracture zone have yielded rattail fish, cuskles, crustations, and ainoderms in the limited trolling that has been done. And at the center of all of this, deeper than any of the surrounding data points, sits the floor of the diamantina deep,
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which has contributed nothing to the biological record because nothing has been collected from it. The picture that emerges is not one of a mysterious void that might harbor sea monsters. It is something more interesting than that and more scientifically meaningful. It is
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the picture of a deep sea ecosystem that almost certainly exists that is fed by a productive overlying ocean that sits in geological isolation sufficient to have produced unique evolutionary trajectories over tens of millions of years and that has simply never been
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examined. The signals from the surrounding environment, the whales, the squid, the bioluminescence, the acoustic complexity are not clues to something supernatural.
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They're indicators of biological richness in a region that extends in principle all the way down to the floor of the deep. They are the context in which the hadal zone of the diamantina exists. And they make the case quietly
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and circumstantially that the floor of the diamantina is not empty. The honest answer to the question of what lives in the diamantina deep is that we do not know. But the honest answer to the question of whether something lives
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there is almost certainly yes, the surrounding environment is too rich, the food supply too consistent, the geological history too long, and the analogies from other hadal systems too clear for the alternative to be plausible. The deep floor of the
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Diamantina is in all probability inhabited by organisms that have never been seen, never been named, and never been studied. what those organisms look like, how they are related to species found in other Hadal systems, what metabolic strategies they use to survive
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at 800 atmospheres of pressure in near freezing water, and what role they play in the broader biogeeochemical cycling of the Indian Ocean deep are questions that remain entirely open. And that is precisely what makes the Diamantina deep so compelling as a scientific target. It
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is not compelling because it is dramatic or because it promises monsters. It is compelling because it is a large geologically distinct biologically isolated hadal system sitting in an ocean that has been undersampled at depth fed by a productive overlying
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ecosystem and surrounded by a growing body of evidence that the Indian Ocean deep supports unique and diverse hadal communities. Every piece of the puzzle points toward the same conclusion. The expedition simply has not happened yet.
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And when it does, the question of what the Diamantina has been hiding for all these millions of years may finally begin to find an answer. What that answer might look like and what a real expedition to the floor of the
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Diamantina Deep would actually involve is where the story turns next. So, let us think about what that expedition might actually look like. Not in the abstract, not as a vague scientific wish, but as a concrete plan, the kind
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that researchers have drafted for other Hadal systems, and that could, with the right funding and the right vessel, be applied to the Diamantina.
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A realistic campaign would probably begin in Fremantle, the port city just south of Perth that serves as the primary departure point for Australian oceanographic research in the eastern Indian Ocean. From there, a vessel equipped for deep sea lander operations
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would need roughly four to 5 days of transit to reach the Diamantina fracture zone, depending on sea conditions and the exact target coordinates.
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The southeastern Indian Ocean is not a gentle ocean. Swells in that region can exceed 4 m even in relatively calm periods, and the weather window for stable deep sea operations is narrower than in some other ocean basins.
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Planning an expedition for the oustral summer roughly November through February would give the best odds of workable conditions, though not a guarantee. The Southern Ocean does not negotiate.
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Once on site, the core tool of the expedition would be freef fall landers. These are relatively simple in concept, but demanding an execution. A lander is essentially a weighted frame carrying scientific instruments, cameras, bait containers, and sampling equipment. It
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is released from the ship and allowed to sink freely to the bottom, which at 8,047 m takes roughly 3 to 4 hours, depending on the descent rate. It sits on the seafloor for a programmed period, typically 12 to 24 hours, recording
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whatever approaches the bait. Then an acoustic signal from the ship triggers a release mechanism that drops the ballast weights and the lander, now positively buoyant thanks to glossphere flotation arrays, rises back to the surface over another 3 to 4 hours. The ship then
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tracks and recovers it. A single lander deployment and recovery cycle takes the better part of 2 days. A 14-day expedition on site could realistically complete five to eight full lander deployments, which is enough to begin building a picture of what lives at the
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bottom. The bait used in hadal lander work is typically mackerel or similar oily fish because the scent disperses well in the near zero current conditions of the hadal floor and attracts scavengers from a distance. Cameras mounted on the lander frame record
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whatever arrives. In wellstudied trenches, the footage from bait camera landers is often striking. Amphipods arrive within minutes of the lander touching down, sometimes in swarms so dense they obscure the bait entirely. Snailfish appear at slightly greater distances, moving in slow, deliberate arcs around
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the frame. Holurans, the sea cucumbers of the deep, move across the sediment in the background, seemingly indifferent to the commotion. Polyat worms emerge from the sediment surface. Occasionally, something larger and less identifiable passes through the frame. In the
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Diamantina, that footage would be entirely new. Every organism that appeared on screen would be at minimum a potential new record for the region, and many would likely be undescribed species. Beyond the bait cameras, a welle equipped expedition would carry
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sediment corers which punch into the seafloor and retrieve a cylinder of sediment that can be analyzed for microbial communities. Mayoa for a minifera and geochemical signatures. A sediment core from the Diamantina deep would tell researchers about the organic
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input history of the site, the composition of the microbial community living in the sediment, and the physical structure of the bottom environment.
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These cores are not glamorous, but they carry enormous scientific information. The microbial data alone from a single wellpreserved core from 8,047 m could support years of laboratory research.
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Water column sampling at multiple depths during the transit down and back up would add another layer. Niskin bottles triggered at specific depths collect water samples that can be filtered for particular organic matter, analyzed for dissolved oxygen and nutrient chemistry
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and processed for environmental DNA. The Edna approach is relatively new in Hadal research, but has already proven valuable in other deep sea contexts.
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By filtering water and extracting the genetic fragments shed by organisms passing through, researchers can detect the presence of species without ever physically capturing them. A snail fish that swims through a water mass leaves behind cells, mucus, and genetic
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material that a sensitive eda assay can detect and in some cases identify to species level or at least a family.
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applied to the water column above the Diamantina deep. Edna sampling could reveal the presence of organisms that a bait camera would never attract and that a troll would never catch. It is a way of listening to the water. What would
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the expedition likely find? Here it is worth being careful because the honest answer is that we do not know precisely and part of the value of the expedition is that it would tell us things we cannot predict. But based on what has
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been found in analogous hadal systems, some reasonable expectations can be sketched out. Amphipods are almost certain to be present. They are found in every hadal zone that has been sampled with bait and they are often the numerically dominant macroaer atal
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depths. The species present in the diiamantina would almost certainly differ from those found in the Marana, the Keradec or the Java trench. Research in the Kerdc Trench found that a substantial proportion of its amphipod species were endemic to that system
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found nowhere else on Earth. The Diamantina geologically isolated from Pacific had systems by the mid ocean ridge systems of the Indian Ocean and separated from the Java trench by thousands of kilometers of abyssal plane would have had its own evolutionary
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history. Its amphipods, if present, would likely be distinct. Naming and describing those species would add meaningfully to the global catalog of hadal biodiversity, which currently lists fewer than 400 described hadal species across all ocean trenches and deeps combined. That number
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is almost certainly a severe undercount, but it is what the current literature contains. Snailfish are a more uncertain prospect, but not an unreasonable one.
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The family lip paradai has produced hadal adapted species in the Pacific with pseudo liparis swary recorded at 8,336 m in the Marana trench in 2023 and other lipid species documented in the Kerdc and Tonga trenches. The Java Trench, the
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deepest point in the Indian Ocean at approximately 7,290 m, yielded snailfish observations during the 2019 five deeps expedition. The Diamantina at 8,047 m is deeper than the Java Trench and the Indian Ocean lipid fauna is poorly characterized. Whether a
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snailfish lineage has colonized the Diamantina deep and how it might differ from its Java trench relatives is a genuinely open question. The answer would have implications for understanding how snailfish have dispersed and adapted across the global hadal environment. Polycate worms are
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almost certain to be present in the sediment, though they would require careful sediment sampling to recover.
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Polyats are among the most species rich groups in the deep sea and adal sediments consistently yield new species when examined carefully. They are not charismatic but they are ecologically important as processes of organic material in the sediment and the species
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found in the diamondina would add to a poorly known global fauna. The microbial findings might ultimately be the most scientifically significant.
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Hadal sediments are consistently found to harbor high densities of microbial cells often exceeding those of surrounding abyssal planes due to the concentration of organic matter in the topographic low. The microbial communities in different hadal systems are distinct reflecting the different
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chemical environments, sediment compositions and organic input histories of each site. The Diamantina's sediment composed largely of salicious ooze and clay would support a microbial community adapted to those specific conditions.
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Isolating novel microbial strains from diamantina sediments would be valuable in its own right as basic science. But it also has potential applied dimensions. Pisophilic bacteria, organisms that require or prefer high pressure to function, produce enzymes that are stable under conditions that
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would dene ordinary proteins. Enzymes from hadal bacteria have already attracted interest from industrial biotechnology, particularly DNA polymerises and proteases that remain active under conditions where conventional enzymes fail. A new Hadal microbial community from the Diamantina could yield novel
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enzyatic capabilities. This is not a guarantee and it is worth being clear that the primary scientific value of such an expedition is the basic knowledge it would generate, not any immediate commercial application. But the applied potential is real and has
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been demonstrated in other Hadel systems. The total scientific output of a 14-day Dantina expedition, even a modest one using freefall landers and water column sampling without a crude submersible, would likely include multiple new species descriptions, the first characterization of the microbial
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community at the deepest point in the eastern Indian Ocean, the first Edna profile of the water column above the deep, and the first direct visual record of the hadal fora of the Diamantina system.
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Each of those outputs would represent a genuine first in the scientific literature. The papers that emerge from such an expedition would not be incremental additions to a wellestablished body of knowledge. They would be the beginning of that body of
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knowledge. The cost of such an expedition is worth considering because it is one of the main reasons it has not happened yet. A focused lander campaign using a suitable research vessel with the full suite of sampling equipment and
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a scientific team of perhaps 10 to 15 people would likely run somewhere between 1 and 3 million US depending on vessel day rates, equipment costs, and transit time. That is not a trivial sum, but is not extraordinary by the
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standards of oceanographic research. It is roughly comparable to a moderate size grant from a national science foundation and it is a fraction of the cost of a crude submersible expedition. The five deeps expedition which used the DSV limiting factor to reach the deepest
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points of all five oceans was funded privately by explorer and businessman Victor Visco at an estimated cost of well over $48 million across the full campaign. A Diamantina lander expedition would be far more modest in scale and far more accessible in cost. It is the
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kind of project that could be funded through a combination of national agency support, international collaboration, and potentially private partnership if the right proposal reached the right decision makers at the right time. What is perhaps most striking about the
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Diamantina deep as a scientific target is how straightforwardly compelling the case for exploring it actually is. It is not a speculative or marginal site. It is one of the deepest points in any ocean. It sits in a geologically
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distinct fracture zone that has been isolated from Pacific Hadal systems for tens of millions of years. It is surrounded by a biologically productive ocean and over lane by a water column that supports a rich community of midwater and deep water organisms. Every
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hadal system that has been examined has yielded new species. The Indian Ocean Hadal zone is the least studied of any ocean's deep environment. The technology to conduct a meaningful biological survey of the Diamantina exists and has been used successfully in other
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locations. The scientific return would be high and the cost by the standards of deep sea research is not prohibitive.
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The case, in other words, essentially makes itself. And yet, the expedition has not happened. The Deiamatina Deep sits at 8,047 m in the eastern Indian Ocean as it has for tens of millions of years. And whatever lives on its floor has never
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been observed, never been sampled, never been named. The organisms down there, if they are anything like what analogous systems have produced, are going about whatever it is they do in the cold and the dark and the pressure, entirely
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indifferent to the fact that no human has ever seen them. They have been there long before anyone thought to look, and they will continue to be there until someone finally does. That moment when a lander finally touches down on the floor
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of the Dear Hamantina Deep and a camera begins recording may come sooner than it has in the past. The global momentum behind deep sea exploration has been building. The Five Deeps expedition demonstrated that reaching the deepest points of all five oceans was
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technically achievable. The seabed 2030 project has drawn renewed attention to how much of the seafloor remains unmapped.
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Edna technology has lowered the barrier to biological sampling in remote locations and the scientific community's understanding of Hadal biodiversity has grown enough that the value of sampling new Hadal systems is now much better appreciated than it was a generation
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ago. The Diamantina is in that context an obvious next step. It is the kind of place that once someone finally goes there will make researchers wonder why it took so long and what that first look might reveal in the cold darkness at the
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bottom of one of Earth's least known places is where the story arrives at last. So picture it just for a moment.
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8,047 m of water pressing down in complete darkness. The temperature sitting somewhere just above freezing around 1 and 12 to 2° C. Cold enough to feel like the edge of something. Cold enough that the word cold barely covers it.
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The pressure at that depth is approximately 800 atmospheres. Which means that every square cm of surface down there is bearing a weight equivalent to 800 times what the air above us exerts right now. Wherever you're sitting or lying, whatever the
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temperature is outside your window tonight. Nothing about that place is comfortable by any measure we would recognize. And yet something lives there. Almost certainly something lives there. It has been living there in some form for a very long time. The
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Diamantina Deep was given its name in 1960 when HMAS Diamantina, an Australian riverclass frigot that had been converted for oceanographic survey work, passed over that stretch of the eastern Indian Ocean and measured the depth below it. The number came back at
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roughly 8,047 m, recorded near the coordinates of approximately 35° south, 105° east. The ship moved on. The deep stayed where it was, as it always had. It did not need naming to exist. It did not need a human
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ship passing overhead to be real. It had been there for tens of millions of years before that moment, shaped by the slow movement of the Indo-Australian plate and the fracturing of old oceanic crust along a transform fault system that
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stretches roughly 2,500 km east to west. The name was given by the people who measured it. The place itself belongs to no one. What strikes you sitting with this for a while is that the Diamantina deep is not some obscure footnote in the
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catalog of Earth's geography. It is one of the deepest points in any ocean on the planet. It sits in the Indian Ocean which covers roughly 70 million km and connects the waters of three continents.
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It is not hidden in some far corner of an already remote ocean. It is a significant geographical feature by any standard. And yet, as of right now, no crude vehicle has ever descended into it. No dedicated biological lander has
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ever touched its floor. No camera has ever recorded what moves or rests or filters the water at the bottom of it.
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The organisms that live at 8,047 m in the Diamantina fracture zone, if they are anything like what similar hadal systems have produced elsewhere, have never been seen by human eyes. They have never been named. They exist in a state
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of complete scientific anonymity, not because they are absent, but simply because no one has gone to look. That's a remarkable thing to sit with in the 21st century. We live in an era of satellite imaging capable of resolving
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objects less than a meter across from orbit. We have sent probes to the outer edges of the solar system and received back images of Pluto's surface. We have mapped the surface of Mars in higher resolution than we have mapped the floor
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of the Indian Ocean. The Seabed 2030 project, a collaboration between the Nippon Foundation and the General Baimetric Chart of the Oceans, identified the Diamantina region as one of the least mapped deep zones in any ocean. And the project's goal of mapping
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the entire seafloor to meaningful resolution by the end of this decade is still very much a work in progress. The ocean covers roughly 71% of Earth's surface. Less than 25% of the seafloor has been mapped to high resolution. The
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Diamantina is not an anomaly in that context. It is a symptom of something much larger. The fact that the deep ocean as a whole remains the least explored environment on the planet we live on. But knowing that does not make
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the Diamantina feel less extraordinary. If anything, it makes it feel more so because the Diamantina is not just unmapped. It is biologically unknown.
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And there is a difference between those two things. A place can be unmapped and still have its basic nature understood, still fit within a framework of what we know about similar environments.
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The Diamantina does not fit neatly into that kind of reassurance. Its geological structure is distinct from the subduction trenches of the Pacific. its oceanographic conditions, including lower dissolved oxygen levels, warmer deep water than Pacific equivalents, and a restricted deep water circulation
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pattern shaped by the Indian Ocean's mid ocean ridge systems create an environment that does not map cleanly onto what we have learned from the Marana or the KerdC or the Tonga trenches. Whatever biological community has evolved in the Diamantina deep has
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done so in its own specific conditions over its own specific time scale in isolation from the hadal forasers of other oceans. Every hadal system that has been studied has turned out to be distinct. The amphipod communities of the Kerdc trench are different from
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those of the Marana. The snail fish observed in the Java trench during the 2019 five deeps expedition were different from those recorded at 8,336 m in the Mariana in 2023. The principle of alipatric speciation where population separated by geographical barriers
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evolve independently over time applies with particular force in hadal environments because the barriers are absolute. A species adapted to the chemistry and pressure of one trench cannot simply migrate to another.
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The deep ridges and abyssal planes between her dal zones are impossible in any practical biological sense for organisms that require hadal conditions to survive.
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The diamantina has been isolated from Pacific hadal systems for tens of millions of years. Whatever has evolved there has had tens of millions of years to diverge. The currently described catalog of Hadal species, meaning organisms documented from depths below
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6,000 m, contains fewer than 400 described species in total. That number is almost certainly a severe undercount.
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It reflects not the actual diversity of Hadal life, but the extremely limited sampling effort that has been directed at Hadal environments globally. Fewer than 30 expeditions since the year 2000 have targeted depths below 7,000 m with biological sampling equipment. The
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Diamantina deep at 8,047 m has contributed zero to that catalog from its deepest sections. Zero species described from the bottom of one of the deepest places in the Indian Ocean. The number is not a reflection of biological poverty. It is a reflection of the
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absence of any attempt to look. Tonight, right now, while you are wherever you are and the world above the surface is doing whatever it is doing, the Dantina Deep is exactly as it has always been.
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The water at the surface above it in the southeastern Indian Ocean, roughly 1,100 km southwest of Perth, is dark and cold and moving with whatever swells are running tonight. Below the surface, the light fades within the first 200 meters.
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By a thousand meters, it is gone entirely, replaced by the occasional pulse of bioluminescence from organisms moving through the mesopelagic and bathopagic layers. By 4,000 m, the water is close to its final temperature, and the pressure has long since passed any
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threshold a human body could survive without protection. By 6,000 m, you are in the hadal zone. that narrow category of depth that represents less than 2% of the ocean floor by area, but which contains some of the most biologically
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interesting environments on the planet. And then another 2,000 m further down, the floor of the Diamantina.
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Whatever is down there is going about its existence with complete indifference to the fact that no one has named it.
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That is not a poetic exaggeration. It is simply true. The organisms in the Hadal zones of the world's oceans did not begin existing when humans discovered them. The snailish that was filmed at 8,336 m in the Mariana Trench in 2023
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did not come into being at the moment of filming. It was already there. Its ancestors were already there. The same logic applies to whatever is living at the bottom of the Diamantina.
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It has a history that predates human awareness of it by an enormous margin. It has adapted over generations too numerous to count to exactly the conditions it lives in. 800 atmospheres of pressure, near freezing temperatures, complete darkness, a slow rain of
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organic particles from the water column above. Whatever chemical gradients exist in the sediment and along the fracture zone walls, that is its entire world and it functions in that world with whatever biology it has developed to do so. There
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is something quietly humbling about that, not in a dramatic existential crisis kind of way, but in a simpler, more grounded sense. We tend to think of Earth as a known place. We have been living on it for a very long time. We
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have named its mountains and its rivers and its ocean basins. We have measured the height of Everest and the depth of the Challenger Deep and the temperature of the Sahara in August. We have a strong intuition that the planet has
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been figured out, at least in its broad outlines. And then you think about the Diamantina and that intuition softens a little because here is a place that is not at the edge of the world in any metaphorical sense. It is in the middle
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of an ocean that borders three continents. It has been known to exist in the sense of having a recorded depth measurement since 1960. And it is biologically speaking essentially a blank. Not a partial picture, not a rough sketch, a blank. The ocean as a
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whole is like this to a degree that is genuinely difficult to absorb. The deep sea is the largest living space on Earth by volume and it is also the least known. The Diamantina is one expression of that, a particularly striking one
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because of its depth and its geological distinctiveness, but not a unique exception. There are other hadal zones that have received little or no biological attention. There are bissell plains stretching for thousands of kilome that have never had a sediment
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core taken from them. There are mid ocean ridge systems where the hydrothermal vent communities which can be extraordinarily rich in life have never been directly observed. The Diamantina sits within this larger context of oceanic unknowing and it is
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worth holding that context in mind because it means that the Diamantina is not a curiosity. It is a reminder of how much of the world we share with organisms we have never encountered.
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What a future expedition to the Diamantina might find is of course genuinely uncertain. Science does not guarantee discoveries on a schedule. A lander dropped to the floor of the Diamantina might return footage that is sparse or difficult to interpret or that
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raises more questions than it answers. That is how science often works, especially in environments as poorly understood as this one. But based on what analogous hadal systems have produced, a reasonable expectation would include new amphipod species, given that
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amphipods are the most consistently abundant macro in hadal sediments and that every wells sampled had zone has yielded undescribed species. It would likely include new polyat worms which are among the most species rich groups in deep sea environments. It might
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include lipid fish, the snail fish family that has independently colonized multiple Adal zones and that has proven remarkably adaptable to extreme depth.
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Though whether they reach the deeper sections of the Diamantina would depend on conditions we do not yet know. And it would almost certainly include a microbial community unlike any previously characterized, shaped by the specific sediment chemistry, pressure, and temperature regime of the
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Diamantina's floor. Each of those findings would be a first. Not an incremental addition to a long list, but an actual first. The first species described from the deepest point of the eastern Indian Ocean. The first microbial profile of a hadle sediment in
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the Diamantina fracture zone. The first visual record of any organism living at 8,047 m in this part of the world. Those firsts matter, not just as novelties, but as scientific baselines.
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You cannot understand howal ecosystems vary across the global ocean without sampling them. You cannot build a complete picture of deep sea biodiversity without including the places that have not yet been included.
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The Diamantina is a gap in that picture and it is a significant one. The momentum toward filling that gap has been building slowly but genuinely. The five deeps expedition completed between 2018 and 2019 demonstrated that reaching the deepest points of all five oceans
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was technically achievable with modern equipment. The DSV limiting factor, the full ocean depth submersible used in that campaign, visited the deepest point of the Indian Ocean at the Java Trench in 2019, descending to approximately 7,192 m and recording snail fish and amphipods
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in the process. The Diamantina at 8,047 m is deeper than the Java Trench and would require the same class of equipment to reach with a crude vehicle.
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But a crude descent is not the only option. And in many ways, a carefully designed lander campaign using freeful systems with bait cameras, sediment corers, and water samplers would produce more biological data per dollar spent than a crude dive. The technology is
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available. The scientific case is clear. The cost is real, but not prohibitive. What has been missing so far is the convergence of funding, institutional will, and expedition planning that would put a research vessel over the Diamantina with the right equipment
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aboard. That convergence may come. It may come in the next few years as interest in Indian Ocean deep sea biology grows and as the global mapping effort draws more attention to how little is known about this region. It
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may come from an Australian institution given the Diamantina's proximity to Perth and the historical connection through HMAS Diamantina's original survey.
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It may come from an international collaboration perhaps involving Cesuro or a European oceanographic institution or a private expedition following in the footsteps of the five deeps. However it comes, the moment it does, the Diamantina will stop being a blank and
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start being a place with a record. The organisms living there will stop being hypothetical and start being named. The floor of the deep will stop being imagined and start being seen. Until that happens, the Diamantina continues to exist exactly as it does right now.
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8,047 m deep, cold, pressurized, dark, and full of whatever life has made its home there over the course of geological time. The water above it moves. The marine snow drifts down through the layers, slowly, carrying the organic remnants of surface life into the deep.
Speaker A
The organisms on the floor, whatever they are, do whatever they do. They have been doing it for a very long time. They will keep doing it whether anyone comes to look or not. But it would be something, wouldn't it, to finally look.
Speaker A
Thank you for spending this time with life beyond scene. If you have a thought about what might be living at the bottom of the Diamantina Deep, or if you found something in tonight's narration that stayed with you, please leave it in the
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comments. This channel runs on curiosity and your thoughts genuinely shape where we go next. If you enjoyed this, a like goes a long way and subscribing means you will be here for the next journey.
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Wherever you are tonight, whatever the temperature is, whatever hour it is where you're sitting, thank you for listening. Sleep well.
Topics:Diamantina Deephadal zoneIndian OceanDiamantina Fracture Zonedeep sea explorationocean trenchHMAS Diamantinahadal biologyunexplored ocean
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