The ocean floor is riddled with ungodly species that seem to have been created out of our worst collective nightmares. There are demonic-looking fishes that glow and sponges (that do not look like SpongeBob) that devour the ancient remains of other animals. But organisms along the ocean floor are biological carbon sinks that trap carbon dioxide from our atmosphere.
A group of researchers from NRS/Genoscope and IFREMER in France, the University of Geneva, the Norwegian Research Centre, and Bjerknes Centre for Climate Research looked at ocean floor samples from around the world and the DNA they contained. They found that almost two-thirds of the lifeforms represented by the DNA are undiscovered organisms. According to their study, diverse and unknown plankton are sequestering carbon dioxide in the deep sediment, particularly in “hotspots” near Earth’s poles.
These undiscovered plankton are part of the biological carbon pump, a crucial planetary system that transfers carbon from the atmosphere to the seafloor, where it is stored for potentially millions of years. Through this “pump,” plankton and other organisms take in carbon dioxide at the upper levels of the ocean and eventually carry it in their bodily tissues to the seafloor—usually because they’ve died and sank. The new study found, though, that it’s not just dead, sunken plankton down there; there are a whole lot of living, undiscovered critters, too. This carbon is sequestered in the deep darkness, out of the atmosphere where it would absorb heat and contribute to the greenhouse effect.
“For the first time, we can understand which members of plankton communities are contributing most to the biological pump, arguably the most fundamental ecosystem processes in the oceans,” Colomban de Vargas, a researcher at CNRS in France, said in a press release.
The research team created a database from more than 400 samples of deep ocean sediments that were collected between 2010 and 2016. They compared that to approximately 1,300 other previously collected samples, according to their paper, which was published in the journal Science Advances earlier this month. “This provides the first unified vision of the full ocean eukaryotic biodiversity, from the surface to the deep-ocean sediment, allowing marine ecological questions to be addressed for the first time at a global scale and across the three-dimensional space of the ocean, representing a major step towards ‘One Ocean ecology,’” the researchers said in a press release.
Not only did they find diverse plankton in the sediments that help with sequestration, but they were also able to confirm that polar regions are “hotspots” of carbon sequestration and that the plankton DNA in the seafloor sediments can predict the strength of the biological pump (also known as a marine carbon pump).
Scientists have estimated that our ocean absorbs about 40% of the carbon dioxide we produce—and these new findings highlight how important the seafloor ecosystem is to this process.
“Our study further demonstrates that deep-sea biodiversity research is of paramount importance. Huge numbers of unknown organisms inhabit ocean-floor sediments and must play a fundamental role in ecological and biogeochemical processes,” researcher Andrew J. Gooday, Emeritus Fellow at the National Oceanography Centre, Southampton, said in a statement. “A better knowledge of this rich diversity is crucial if we are to protect these vast, relatively pristine ecosystems from the impacts of possible future human incursions and understand the effects on it of climate change.”