[Music] the deep sea is a world of extremes so far in this series we've taken a look at the ways in which animals have adapted to survive in the cold dark depths we've explored the ecosystems of this unforgiving realm and seen how communities of life cling to whatever source of energy they can find from vents of superheated water to the carrion of sunken whales but now it's time to dive even deeper and discover a place where life is pushed to its absolute limits for at the bottom of the pacific ocean the sea floor widens into
a gaping abyss of obscurities fish that seem to lack faces sprawling fields of bacteria [Music] and giants that resemble life from another planet let's take a closer look at the hidden world of the mariana trench [Music] the infamous mariana trench sits like a crescent-shaped dent in the floor of the pacific a 2550 kilometer long 69 kilometer wide fracture that plummets down into a pure black void at the bottom it hosts the deepest known location on earth the challenger deep 11 033 meters or 36 200 feet beneath the waves [Music] the trench itself is but one
part of a global network of deep scars that cut across the ocean floor features that formed from a process called subduction in the case of the mariana trench the western edge of the pacific plate was thrust beneath the smaller mariana plate to the west creating the deep fracture molten material then rose through volcanoes near the trench building the nearby mariana islands at its deepest point the mariana trench dips down into a little explored zone of the ocean the hadel zone named after the realm hades the underworld of greek mythology a suitable title for a place
where the conditions of pure darkness acidic freezing water scarce food and immense pressure create a challenging environment for creatures to survive in for much of history it was believed to be a dead zone void of any life at all an impossible frontier and an empty void of perils that could never be reached by any human but in the 19th century this was all about to change the marianas depths were first plumbed in 1875 when the crew aboard the hms challenger cast a weighted sounding line over the side of the vessel and found they needed more
rope they had not expected there to be a location so deep but news of its discovery caught the eye of the ambitious knowing it existed simply wasn't enough and a few dared to venture to the bottom [Music] in 1960 85 years after the challenger deep was discovered on that pioneering voyage two men set out to reach the bottom [Music] jacques piccard and navy lieutenant don walsh sheltered only by a cramped bath escape submersible called the triesta their five-hour descent was fraught with challenges the water pressure near the bottom was nearly a thousand times greater than
atmospheric pressure at sea level during the journey this caused the viewing window to crack limiting their time spent on the sea floor to only 20 minutes even in such a short amount of time what they saw would shock the scientific community life pale shrimp and flounder like fish along with what they described as a dark brown diatomaceous ooze that covered the sea floor pickard described this moment with excitement in a book about the voyage here in an instant was the answer that biologists had asked for the decades could life exist in the greatest depths of
the ocean it could [Music] when james cameron followed in the triesta's footsteps on board the deep sea challenger in 2012 he too saw the sprawling microbial mats bizarre looking filamentous clumps of microorganisms living off chemicals from altered rocks ten thousand nine hundred and twelve meters or thirty five thousand eight hundred and three feet down in a sunless world it is these bacteria that support more complex creatures for without sunlight larger animals must instead rely on the energy produced by bacteria undergoing chemosynthesis the deep sea equivalent to photosynthesis [Music] the footage you're seeing now was taken
by an unmanned japanese submersible called kaiko in 1996 having reached a depth of 10 897 meters it marked the deepest dive for an unmanned submersible at the time its goal was to sample bacteria from the mats that picard and walsh had observed nearly 40 years earlier they found that a number of these bacterial species appeared to be obligately barophilic meaning they thrived under high environmental pressures proving that the idea that life could only exist in more moderate conditions was flawed but in 1998 kaiko returned to the challenger deep and stumbled upon more complex life hirondelia
gigas a gigantic amphipod species this discovery posed a bit of a mystery the extreme pressures of the deep sea cause calcium carbonate that makes up the shells of amphipods and many marine animals to dissolve more readily in water leaving their soft bodies vulnerable as such amphipods are not usually found below about five thousand meters or sixteen thousand four hundred feet and yet here in caicos lights was a giant amphipod retaining even its tough exoskeleton it has since been found that they protect their shells using a form of aluminium armor using chemicals in their gut to
extract aluminium ions from the sea floor mud while they forage for food in their role as detrivores these amphipods occupy a key role in the ecosystem they act as a cleanup crew possessing enzymes that are able to digest even wood in more recent times remote submersibles have caught yet more oddities of the mariana trench in their headlights among the most abundant inhabitants are the holothurians sea cucumbers like the remarkable sea pig with its ring of feeding tentacles that it uses to sift through the mud and grab onto food some scientists believe that pickard's fish was
in fact a sea cucumber for it is thought that fish are unable to survive where the pressure is so great that it would dissolve the bones of any vertebrates the deepest known fish thrives at depths of 8 000 meters or 26 200 feet still two kilometers above the challenger deep the mariana snail fish discovered in 2014 yet given the scientific name sudola paris sui to commemorate sub-lieutenant herbert swire from the hms challenger [Music] but snailfish and amphipods are not the only oddballs found in the trench gigantic xenophianophores grow to be 20 centimeters in diameter yet
consist of only a single cell predatory tunicates called sea squirts anchor their bodies to the sides of canyons in weight of passing prey while deep sea hatchet fish use bioluminescence to blend in with their surroundings while only glimpses of these otherworldly organisms have been recorded their abundance goes to show that life will always find a way to survive even when faced with the intense challenge of living at the heart of the ocean's underworld [Music] despite all the expeditions and the footage that's been gathered we have still only just begun to dip our toes into the
hidden world of the mariana trench [Music] it is likely that many new species await discovery and will help us piece together the puzzle of how animals can survive such extremities researching the marianas microorganisms could lead to vital breakthroughs in biomedicine and biotechnology and shed light on the story of life's emergence on planet earth but even the furthest depths are within reach of human-driven destruction already has plastic been found in a place we scarcely understand who knows what vital discoveries might vanish before we come to understand their importance this portion of the video is sponsored by
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