Thousands of strange creatures found deep in ocean

Cain Burdeau, AP Google News 23 Nov 09;

NEW ORLEANS — The creatures living in the depths of the ocean are as weird and outlandish as the creations in a Dr. Seuss book: tentacled transparent sea cucumbers, primitive "dumbos" that flap ear-like fins, and tubeworms that feed on oil deposits.
A report released Sunday recorded 17,650 species living below 656 feet, the point where sunlight ceases. The findings were the latest update on a 10-year census of marine life.

"Parts of the deep sea that we assumed were homogenous are actually quite complex," said Robert S. Carney, an oceanographer at Louisiana State University and a lead researcher on the deep seas.
Thousands of marine species eke out an existence in the ocean's pitch-black depths by feeding on the snowlike decaying matter that cascades down — even sunken whale bones. Oil and methane also are an energy source for the bottom-dwellers, the report said.
The researchers have found about 5,600 new species on top of the 230,000 known. They hope to add several thousand more by October 2010, when the census will be done.

The scientists say they could announce that a million or more species remain unknown. On land, biologists have catalogued about 1.5 million plants and animals.

They say they've found 5,722 species living in the extreme ocean depths, waters deeper than 3,280 feet.

"The deep sea was considered a desert until not so long ago; it's quite amazing to have documented close to 20,000 forms of life in a zone that was thought to be barren," said Jesse Ausubel with the Alfred P. Sloan Foundation, a sponsor of the census. "The deep sea is the least explored environment on earth."

More than 40 new species of coral were documented on deep-sea mountains, along with cities of brittlestars and anemone gardens. Nearly 500 new species ranging from single-celled creatures to large squid were charted in the abyssal plains and basins.

Also of importance were the 170 new species that get their energy from chemicals spewing from ocean-bottom vents and seeps. Among them was a family of "yeti crabs," which have silky, hairlike filaments on the legs.

In the mid-Atlantic, researchers found 40 new species and 1,000 in all, said Odd Aksel Bergstad, an oceanographer with the University of Bergen in Norway who was reached by telephone in the Azores islands.

"It was a surprise to me to find such rich communities in the middle of the ocean," he said. "There were not even good maps for the area. Our understanding of the biodiversity there was very weak."

More than 2,000 scientists from 80 countries are working to catalog the oceans' species.

Researching the abyss has been costly and difficult because it involved deep-towed cameras, sonar and remotely operated vehicles that cost $50,000 a day to operate, Carney said.

Once the census is complete, the plan is to publish three books: a popular survey of sea life, a second book with chapters for each working group and a third focusing on biodiversity.

Thousands of Strange Sea Creatures Discovered
Charles Q. Choi, LiveScience Yahoo News 22 Nov 09;

The deep sea is teeming with thousands of species that have never known sunlight, explorers now say.

Revealed via cameras towed deep in the sea, sonar and other technologies, a stunning 17,650 species are now known to thrive in an eternal watery darkness. This menagerie of weird creatures, ranging from crabs to shrimp to worms, somehow manage a living in a frigid black world down to roughly 3 miles (5 km) below the ocean waves.

Most of these creatures have adapted to diets based on meager droppings from the sunlit layer above, while others live on sulfur and methane, or bacteria that break down oil, or the sunken bones of dead whales and other implausible foods.

Scientists have inventoried about 17,650 species deeper than 656 feet (200 meters), the edge of darkness, where sunlight no longer penetrates. This number includes some 5,722 species recorded deeper than the black abyss of 3,280 feet (1,000 meters).

"Typically the deep sea is viewed as something beyond concern, a pit, a desert, a wasteland, but what we have found in our work is that there is an incredible diversity of species there, often with striking adaptations that we as yet don't understand yet," researcher Robert Carney of Louisiana State University, co-leader of the Continental Margin Ecosystems on a Worldwide Scale project, told LiveScience.

Tales from the deep

During their voyages, all part of the decade-long Census of Marine Life project involving thousands of scientists from around the world, explorers discovered a diverse collection of species.

JUMBO DUMBO: A very large specimen of a rare primitive finned octopod — nicknamed "Dumbos" because they flap a pair of large ear-like fins to swim, like the cartoon flying elephant — was discovered at roughly 3,280 to 9,840 feet (1,000 to 3,000 meters) during a 2009 voyage to the Mid-Atlantic Ridge led by Michael Vecchione, director of the National Oceanic and Atmospheric Administration's Fisheries National Systematics Lab at the Smithsonian. The jumbo Dumbo was estimated to be about six feet long (2 meters) and, at roughly 13 lbs. (6 kg), the largest of only a few specimens of the species ever obtained. Altogether, nine species of gelatinous "Dumbos" were collected on the Mid-Atlantic Ridge, including one that may be new to science. Scientists were surprised to find such a plentiful and diverse assemblage of these animals, which rank among the largest in the deep sea.

OIL WORM: After a robotic arm lifted a solitary worm from a hole in the floor of the Gulf of Mexico in what looked like ordinary surroundings, crude oil streamed from both the animal and the open hole. The "wildcat" tubeworm had hit a gusher and was dining on chemicals from decomposing oil, a find made at 3,250 feet (990 meters) at a 2007 voyage.

SEE-THROUGH CUCUMBER: An odd transparent sea cucumber, Enypniastes, was seen creeping forward on its many tentacles at about 3/4 inch (2 cm) per minute while sweeping detritus-rich sediment into its mouth. At the end, it bloomed into a startling curved shape and swam away to find another meal, which scientists recorded on video at roughly 1.7 miles deep (2,750 meters) on a 2007 voyage in the Northern Gulf of Mexico.

YETI CRAB: The "yeti crabs" — crabs with furry claws that resemble stories of the yeti, or abominable snowman — were discovered in 2005 south of Easter Island in the South Pacific, living on hydrothermal vents at a depth of roughly 7,200 feet (2,200 meters) along the Pacific-Antarctic Ridge by researchers affiliated with the Biogeography of Deep-Water Chemosynthetic Ecosystems project. "Presumably their furry claws are farming spaces for microbes," Carney explained.

WHALE BONE EATER: The Antarctic's first recorded whalebone-eating worm, Osedax, was discovered on at roughly 1,640 feet (500 meters) during a 2009 voyage to a range of New Zealand seamounts. Scientists attached whalebone snacks to two vehicles and parked them 1800 and 2060 feet (550 and 630 meters) deep near Smith Island by the West Antarctic Peninsula. When they raised the parked vehicles 14 months later, they found new species of Osedax they crowded onto the parked vehicles. Seventeen species had been reported on other fallen whales in such places as the shallow northeast Atlantic off Sweden, the northeast Pacific off California and the northwest Pacific off Japan. A mat of chemosynthetic microbial fauna and the small marine worm Ophryotrocha, which eats bacterial mats, also covered the parked vehicles.

Startling diversity

Scientists said the work is expensive and dangerous (read more about the voyage here), but the diversity of creatures has proven startling.

The deep sea "is the Earth's largest continuous ecosystem and largest habitat for life. It is also the least studied," said researcher Chris German of Woods Hole Oceanographic Institution, co-chair of Biogeography of Deep-Water Chemosynthetic Systems project.

A sample of sediment yields more new species than known species, researchers said. And interest in the newfound creatures goes beyond pure scientific marvel.

"There's a lot of interest in bioprospecting there — pharmaceutical companies are really very interested in what deep-sea fauna have to offer, as they often produce unusual compounds," explained Paul Snelgrove, an oceanographer from Memorial University of Newfoundland in Canada.

Climate change, changes in ocean acidity, and "evidence of pollutants creeping deeper and deeper into the ocean" are all ways in which the newfound deep-sea creatures could be vulnerable to human-induced changes, Snelgrove and other researchers said.

From eternal darkness springs cast of angels and jellied jewels
Frank Pope, Times Online 23 Nov 09;

Beyond the reach of the last tendrils of sunlight, far beneath the waves, lies the planet’s largest — and strangest — habitat. Although long thought too extreme for any form of life, a decade-long exploration has revealed a startling range of exotic new species and alien ways to eke out a living in the perpetual darkness.

Sea angels, jewel squid, helmet jellies and a 2m-wide octopod that flies with ear-like fins are among more than 17,000 new species discovered during 210 expeditions undertaken to explore the deep ocean for the international Census of Marine Life.

More than 300 scientists from 34 nations have crammed themselves into deep-diving submersibles or piloted robots from research vessels on storm-racked seas far above, while automated drones have weaved through undersea chasms never seen by Man. Sediment cores, trawls and dredges have scoured for clues about the nature of the deep.

An expedition to the mid-Atlantic ridge this year by Russia, Brazil, South Africa and Uruguay, discovered what is thought to be a new species related to the octopus, nicknamed the “Jumbo Dumbo” for its passing resemblance to the fictional flying elephant.

“If it came up in a trawl it would just be a lump of jelly, but photograph it from a submersible, and it’s very beautiful and graceful,” said Odd Aksel Bergstad of the University of Bergen, the leader of that cruise. “We know very little about how they live. They’re predators but we don’t know what they feed on or how they reproduce. At least one of the nine kinds we found is probably a new species.

“Because it provides an oasis of topographical relief in the centre of the ocean, we found a high concentration of animals on the Mid-Atlantic Ridge.”

Much life in the deep relies on death in the sunlit waters above. While most food comes from the falling remains of tiny marine organisms, occasionally the biggest animals on the planet crash to the seabed. Seventeen species of “zombie bone-eating worms” — otherwise known as Osedax — survive on the rare bounty of a sunken whale.

In the deep, unidentified species are often the norm, not the exception. One cruise yielded 680 specimens of fly-like copepod, only seven of which could be identified.

“The abyssal fauna is so rich in species diversity and so poorly described that collecting a known species is an anomaly,” said Dr David Billett of the National Oceanography Centre, Southampton. “Describing for the first time all the different species in any coffee cup-sized sample of deep-sea sediment is a daunting challenge.”

“New species aren’t news for deep- ocean scientists, they’re a problem,” agreed Dr Robert Carney of Louisiana State University, one of the leaders of the census. “The figure of 17,000 species is just what’s made the logbooks, it’s what we can deal with. If you want the real figure you can multiply that by a hundred or a thousand.”

The eternal darkness has forced life to find sources of energy other than sunlight. Discovered in the 1970s, deep-sea hydrothermal vents use microbial life to help them to feed from chemicals in the scalding hot water. Less well known is a tubeworm known as Lamellibrachia, found in the Gulf of Mexico, that lives by prospecting for oil.

Like a miniature drill rig, the tubeworm has a short section protruding from the seabed but a long, fragile tube beneath that it uses to probe for petroleum, allowing it to thrive anywhere below 500 metres deep.

Scientists say that study of life within the seabed is vital for determining the viability of schemes to combat climate change by fertilising areas of the ocean to encourage the growth of carbon-consuming microscopic plants.

The census divided the survey into five separate zones: the continental margins, where the shallow shelves fall away to the deep ocean; the mid-Atlantic ridge, a section of the oceanic mountain range that snakes through all oceans but the Arctic; the abyssal plains that separate the two; seamounts, lone underwater mountains and volcanoes thought to number 100,000 but of which only 100 have been sampled in detail; and finally the specialised communities of hydrothermal vents and cold seeps.

Only the “hadal depths”, ocean trenches that plunge as deep as Everest is high, remained out of reach of detailed survey.

Information from the census will be used to inform efforts to protect the diversity and abundance of deep-sea species. Fishing the depths relies on bottom-trawling that can destroy fragile habitats before their existence is even realised. The offshore oil and gas industry is drilling in ever deeper water, and plans to mine rich mineral deposits on the seafloor are in prospect.

Dr Carney worries most about the prospect of the deep sea being used as a dumping ground, despite a current ban. “The question of what we are going to do with all our high-level radioactive waste is unanswered,” he said. “Ignorance is our main enemy. Before anyone starts to consider the deep ocean as a wasteland, we need to know what’s there.”

The Deep-Sea World Beyond Sunlight: Explorers Census 17,650 Ocean Species Between Edge of Darkness and Black Abyss
ScienceDaily 22 Nov 09;

Census of Marine Life scientists have inventoried an astonishing abundance, diversity and distribution of deep sea species that have never known sunlight -- creatures that somehow manage a living in a frigid black world down to 5,000 meters (~3 miles) below the ocean waves.

Revealed via deep-towed cameras, sonar and other vanguard technologies, animals known to thrive in an eternal watery darkness now number 17,650, a diverse collection of species ranging from crabs to shrimp to worms. Most have adapted to diets based on meager droppings from the sunlit layer above, others to diets of bacteria that break down oil, sulfur and methane, the sunken bones of dead whales and other implausible foods.

Five of the Census' 14 field projects plumb the ocean beyond light, each dedicated to the study of life in progressively deeper realms -- from the continental margins (COMARGE: Continental Margins Ecosystems) to the spine-like ridge running down the mid-Atlantic (MAR-ECO: Mid-Atlantic Ridge Ecosystem Project), the submerged mountains rising from the seafloor (CenSeam: Global Census of Marine Life on Seamounts), the muddy floor of ocean plains (CeDAMar: Census of Diversity of Abyssal Marine Life), and the vents, seeps, whale falls and chemically-driven ecosystems found on the margins of mid-ocean ridges and in the deepest ocean trenches (ChEss: Biogeography of Deep-Water Chemosynthetic Systems).

Edward Vanden Berghe, who manages OBIS (Ocean Biogeographic Information System), the Census' inventory of marine life observations, notes that, unsurprisingly, the number of records in the database falls off dramatically at deeper depths -- a function of the dearth of sampling done in the deep sea.

However, Dr. Vanden Berghe reports that OBIS today records 5,722 species for which all recorded observations are deeper than 1,000 meters (~.62 miles) and 17,650 species for which all recorded observations are deeper than 200 meters, the depth where darkness stops photosynthesis.

Scientists working on the deep-sea Census number 344 and span 34 nations.

By the time the 10-year Census concludes in October, 2010, the five deep-sea projects will have collectively fielded more than 210 expeditions, including the first ever MAR-ECO voyage in October-November this year, to explore the Mid-Atlantic Ridge south of the Equator, a scientific collaboration between Russia, Brazil, South Africa and Uruguay.

Each voyage is hugely expensive and challenged by often extreme ocean conditions and requirements that have kept the remotest reaches of Neptune's realm impenetrable until recently.

While the collective findings are still being analyzed for release as part of the final Census report to be released in London on October 4, 2010, scientists say patterns of the abundance, distribution and diversity of deep-sea life around the world are already apparent.

"Abundance is mostly a function of available food and decreases rapidly with depth," says Robert S. Carney of Louisiana State University, co-leader (with Myriam Sibuet of France) of the Census project COMARGE, studying life along the world's continental margins.

"The continental margins are where we find the transition from abundant food made by photosynthesis to darkened poverty. The transitions display the intriguing adaptations and survival strategies of amazing species," says Dr. Carney.

Abundance in the deep sea requires one or more of the following:

* Swift current, which increases an animal's chance of encountering food;
* Long-lived animals, populations of which grow numerous even on a meager diet;
* Abundant food in higher layers that either settles to the depths or to which deep animals can migrate;
* An alternative to photosynthesis of food, such as chemosynthetic production.

"In the bathy- and mesopelagic zones -- the largest 3D deep-sea living space -- animals either have to cope somehow with food scarcity or migrate long distances up to find food," says MAR-ECO project leader Odd Aksel Bergstad of University of Bergen. "Because it provides an oasis of topographical relief in the center of the ocean, we found a high concentration of animals on the Mid-Atlantic Ridge."

"Distribution is pretty straightforward for animals in the deep sea," says Dr. Carney. "The composition of faunal populations changes with depth, likely a consequence of physiology, ecology and the suitability of seafloor habitat condition for certain animals."

"Diversity is harder to understand. Although the mud on the deep sea floor appears monotonous and poor in food, that monotonous mud has a maximum of species diversity on the lower continental margin. To survive in the deep, animals must find and exploit meager or novel resources, and their great diversity in the deep reflects how many ways there are to adapt."

Meeting an unfamiliar Dumbo, and other tales from the deep

Specific discoveries, some beautiful and all pushing back the frontiers of the unknown, illustrate the results of voyages by the five Census projects exploring the dark deep sea.

On two 2009 voyages to the Mid-Atlantic Ridge by MAR-ECO explorers:

* At 2,000 to 2,500 meters (~1.25-1.5 miles): A bizarre, elongated orange animal identified as Neocyema -- only the fifth specimen of the fish ever caught and never before on the Mid-Atlantic Ridge;
* At 1,700 to 4,300 meters (~1-1.9 miles): Coryphaenoides brevibarbis, with tiny bones in its ear, known as otoliths, that have growth bands countable like tree rings to reveal the fish's age. Comparison of age with size shows its growth rate and thus the amount of food in the neighborhood. Called the rat-tail, the fish lives on crustaceans it catches just above the seafloor.
* At 1,000 to 3,000 meters (~.6-1.9 miles): NOAA researchers led by Mike Vecchione of the Smithsonian Institution collected a very large specimen of a rare, primitive animal known as cirrate or finned octopod, commonly called "Dumbos" because they flap a pair of large ear-like fins to swim, akin to the cartoon flying elephant. The jumbo Dumbo netted by Census explorers was estimated to be nearly two meters (~6 feet) long and, at 6 kg (~13 pounds), the largest of only a few specimens of the species ever obtained. Altogether, nine species of gelatinous "Dumbos" were collected on the Mid-Atlantic Ridge, including one that may be new to science. Scientists were surprised to find such a plentiful and diverse assemblage of these animals, which rank among the largest in the deep sea.

On the October-November 2009 voyage to the Mid-Atlantic Ridge by Russian, Brazilian, South African and Uruguayan MAR-ECO explorers:

* At 1,000 meters (~.6 miles): an "indescribable" catch of "invertebrates of all colors, including corals, sea cucumbers and sea urchins. It's hard to believe that such exuberance of life exists a kilometer deep into the ocean."

On a 2007 voyage in the Gulf of Mexico by COMARGE explorers:

* At 990 meters (~.6 miles): A solitary tubeworm (formally known as Lamellibrachia), in what looked like ordinary surroundings. After a robotic arm lifted the worm from a hole in the Gulf floor, however, crude oil streamed from both the animal and the open hole. The "wildcat" tubeworm had hit a gusher and was dining on chemicals from decomposing oil.
* At 2,750 meters (~1.7 miles) in the Northern Gulf of Mexico: an odd transparent sea cucumber, Enypniastes, was videorecorded creeping forward on its many tentacles at about 2 cm (~.8 inches) per minute while sweeping detritus-rich sediment into its mouth. At the end, it blooms into a startling curved shape and swims away to find another meal

On a just-ended 36-day voyage to the Cayman Trough in the Caribbean, the setting of the 1989, fictional film The Abyss, ChEss explorers were poised to explore the deepest hot-springs on Earth: only to be thwarted by the arrival of tropical storm Ida. Neverthless:

* Working at depths of greater than 4,000 meters (~2.5 miles): Chris German of Woods Hole Oceanographic Institution, ChEss co-chair, and colleagues from the US, UK and Japan found evidence for chemically enriched plumes in the water column signaling the presence of seafloor hot vents hundreds of meters deeper still. Funded by NASA's Astrobiology program, the team used WHOI's new hybrid robotic vehicle, Nereus, first as a free-swimming autonomous underwater vehicle (AUV) and then as a tethered, battery powered remotely operated vehicle (ROV) to track the plume to its source and begin to investigate the seafloor. Bad weather forced the team to break off only hundreds of meters from their target -- a search that will now be resumed by ChEss using the UK's AUV Autosub 6000 and ROV Isis in 2010.

On a 2009 voyage to a range of New Zealand seamounts, a CenSeam team found:

* At 1,000 meters (~.6 miles) and below: abundant vibrant coral gardens in an area of seamounts eerily nicknamed "the Graveyard," where the speed of currents provides ideal habitat for these animals that feed on suspended food. The scientists, who also explored the nearby Andes seamounts, discovered diverse communities living amid the cold water corals, including invertebrates like sponges and seastars and a species of worm that lives within the branches of bamboo corals (Family Isididae), modifying how the corals grow.

On a 2009 voyage to the Antarctic and Southern Ocean a CeDAMar team trapped deep-sea life:

* At about 500 meters (~.3 miles): the Antarctic's first recorded whalebone-eating worm, Osedax. Seventeen species had been reported on other fallen whales in such places as the shallow northeast Atlantic off Sweden, the northeast Pacific off California and the northwest Pacific off Japan. CeDAMar scientists attached whalebone snacks to two vehicles and parked them 550 and 630 meters (~.34-.39 meters) deep near Smith Island near the West Antarctic Peninsula. When they raised the parked vehicles after 14 months, they found the same creatures in the Southern and Antarctic Oceans. Analyzing the populations crowded onto the parked vehicles they found new species of the whalebone-eating genus Osedax. A mat of chemosynthetic microbial fauna and the small marine worm Ophryotrocha that eats bacterial mats covered the raised vehicles.

Diversity and abundance in mud: the living skin of the abyss

On the abyssal floor, the deep mud contains biodiversity that escapes detection by video and photography since most of the animals are only a few millimeters in size and hide among the sediment particles.

"Some scientists have likened deep mud's biodiversity to that of tropical forests. In college I was taught that high biodiversity is a function of habitat diversity -- many nooks and crannies. It is, however, hard to imagine anything as monotonous, nook-less and cranny-less as deep-sea mud," says Dr. Carney.

Sometimes, the vast majority of creatures collected in mud from the abyssal plains are new to science, says CeDAMar expert David Billett of UK's National Oceanography Centre.

Of some 680 specimens of copepods collected on a recent CeDAMar cruise (DIVA 2) to the southeastern Atlantic, for example, only seven could be identified; 99 percent were new to science. And among hundreds of species of macrofauna (animals about the size of an earthworm) collected in different areas, 50 to 85 percent were unrecognized.

"The abyssal fauna is so rich in species diversity and so poorly described that collecting a known species is an anomaly," says Dr. Billett. "Describing for the first time all the different species in any coffee cup-sized sample of deep-sea sediment is a daunting challenge."

Far rarer than new species in the mud is the capture of a new species of sea cucumber, and rarer still a new genus. However, Dr. Billett and colleagues from the National Oceanography Centre and the Shirshov Institute, Moscow, accomplished this feat this year around the Crozet Islands after steaming for a grueling six days south from South Africa.

One of the new sea cucumbers was yellowish-green, a rare find as virtually all others found in the global seas are whitish grey or purple.

However, what startled researchers most was finding that the most abundant sea cucumber around the Crozet Islands -- thousands of specimens at abyssal depths -- was a species never seen anywhere else before, now dubbed Peniagone crozeti.

"The distribution of species in the deep sea is full of mysteries," says Dr. Billett. "In addition to the boundaries caused by underwater topography, ridges and seamounts, there are unseen, and as yet unexplained, walls and barriers that determine supplies of food and define the provinces of species in the deep sea."

"There is both a great lack of information about the 'abyss' and substantial misinformation," says Dr. Carney.

"Many species live there. However, the abyss has long been viewed as a desert. Worse, it was viewed as a wasteland where few to no environmental impacts could be of any concern. 'Mine it, drill it, dispose into it, or fish it -- what could possibly be impacted? And, if there is an impact, the abyss is vast and best yet, hidden from sight.'

"Census of Marine Life deep realm scientists see and are concerned."

Expensive, dangerous work

"The deep sea is the Earth's largest continuous ecosystem and largest habitat for life. It is also the least studied," says Dr. German.

Sampling at great depths depends on high tech instruments (such as remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), and submarines) or "traditional" equipment (trawls, cores, dredges) that need several kilometers of cable to reach the seabed. For example, 12 km (~7.5 miles) of cable was needed to trawl recently down to 4,800 meters (~ 3 miles) depth on the Porcupine Abyssal Plain in the Northeast Atlantic.

Earlier this year, CenSeam scientists aboard New Zealand-based Research Vessel Tangaroa underlined the grueling nature of the challenge of obtaining samples, maps and unprecedented underwater footage of the Graveyard and the Andes seamounts in the South Pacific.

The work was performed with a Deep-Towed Imaging System (DTIS), a technology developed and refined by growing experience over rugged, unfamiliar seamounts and ridges, yielding steadily better results.

Says Mireille Consalvey of the New Zealand National Institute of Water and Atmospheric Research, CenSeam project manager, "Every deployment is a trip into the unknown, with often seasick scientists struggling to work amid high winds and 10 meter swells."

"It can be a tough environment down there. I recall once the abject fear when our video imaging system snagged for 40 minutes on a rock face -- the slow, scary process of recovering it, and the shared worry that our valued recording equipment would arrive at the surface battered and bent. Thankfully, the recorder survived the ordeal better than many of us and yielded brilliant new footage of this remote realm."

One final note about life in the abyss: not all intruders from the lighted world are ROVs or submarines. A southern elephant seal tagged by Census project TOPP recently dove down 2,388 meters (~1.5 miles) from the surface. At that depth, water pressure is roughly equal to 240 times the air pressure at sea level. The human eardrum can rupture at 10 meters.

Adapted from materials provided by Census of Marine Life.