The Mariana Trench is full of microbial activityMore evidence that the old saying "life always finds a way" is correct was found at the deepest point of the planet's oceans, the Mariana Trench. Recently in the news because of James Cameron's expedition there, the trench is 2,550 km long (1,580 miles), and it bottoms out (as far as we can tell) at 10.911 km (10,911 ± 40 m) or 6.831 mi (36,069 ± 131 ft).
Mr. Cameron didn't see anything alive when he was there, but that's only because it couldn't be seen with the naked eye. Despite a water pressure equivalent to 1100x the pressure we have at the surface, the bottom of the trench is full of microbes, according to scientists at the University of Southern Denmark in Odense who have taken a closer look at sediment samples.
Interestingly, the biggest challenge for life at these depths is not the pressure but finding enough food, as only about 1 percent of the organic matter near the surface reaches the abyssal plains that cover most of the deep ocean. But trenches like the Mariana can help by acting as a kind of funnel that captures more organic matter and delivers it to the micro-organisms at the bottom.
[Ronnie Glud]'s team compared sediment samples taken from Challenger Deep and a reference site on the nearby abyssal plain. The bacteria at Challenger Deep were around 10 times as abundant as those on the abyssal plain, with every cubic centimetre of sediment containing 10 million microbes. The deep microbes were also twice as active as their shallower kin. (source)
Here's a video by NOAA that shows where the Mariana trench is and what it kinds of look like (in CGI):
Via New Scientist