There is abundant life at 36,000 feet below the ocean surface, living under the kind of pressure (more than 1,000 times atmospheric pressure at sea level) that would crush human bones down to liquid, according to the first data from a 2010 robotic exploration of the sediments in the Mariana Trench, in the western Pacific Ocean.
Bacterial communities are 10 times more active at the bottom of that trench than in the plains surrounding the trench, according to the findings, published in Nature Geoscience.
“The deep sea trenches are some of the last remaining ‘white spots’ on the world map. We know very little about what is going on down there or which impact the deep sea trenches have on the global carbon cycle as well as climate regulation,” said lead author Ronnie Glud, a biochemist from Nordic Center for Earth Evolution at the University of Southern Denmark.
Earthquakes may be shaking organic matter — dead animals, algae and other microbes — from these plains into the trenches, providing a feast for the bacteria that thrive there, according to the research team.
This makes the bacterial colonies an important factor in the long-term carbon cycle of the ocean, a process that interests scientists studying such topics as climate change.
Glud was joined by researchers from Germany, Japan, Scotland and Denmark. The team used a massive robot to collect sediment in the trench and measure the distribution of oxygen in them, which can be used to deduce microbial activity.
That measurement was done at the bottom of the trench, not in a laboratory.
“If we retrieve samples from the seabed to investigate them in the laboratory, many of the microorganisms that have adapted to life at these extreme conditions will die, due to the changes in temperature and pressure,” Glud said.
That means no threat to oxygen thieves on the surface like us. So, how did this complex team of multi-cellular life spy on the beasties?
One of the team’s methods was to measure the distribution of oxygen into these trench sediments as this can be related to the activity of microbes in the sediments. It is technically and logistically challenging to perform such measurements at great depths, but it is necessary in order to get accurate data on rates of bacterial activity. “If we retrieve samples from the seabed to investigate them in the laboratory, many of the microorganisms that have adapted to life at these extreme conditions will die, due to the changes in temperature and pressure. Therefore, we have developed instruments that can autonomously perform preprogrammed measuring routines directly on the seabed at the extreme pressure of the Marianas Trench”, says Ronnie Glud. The research team has, together with different companies, designed the underwater robot which stands almost 4 m tall and weighs 600 kg. Among other things, the robot is equipped with ultrathin sensors that are gently inserted into the seabed to measure the distribution of oxygen at a high spatial resolution.
“We have also made videos from the bottom of the Mariana Trench, and they confirm that there are very few large animals at these depths. Rather, we find a world dominated by microbes that are adapted to function effectively at conditions highly inhospitable to most higher organisms”, says Ronnie Glud.
On one hand, infection is not an issue, but then I wonder what benefits, in terms of medicine or technology are sitting on the bottom.