Fueling a deep-sea ecosystem: Surprisingly productive microbes are a key source of food in the abyss

Date: June 11, 2018

Source: Phys Org
Author: Woods Hole Oceanographic Institution

Miles beneath the ocean’s surface in the dark abyss, vast communities of subseafloor microbes at deep-sea hot springs are converting chemicals into energy that allows deep-sea life to survive—and even thrive—in a world without sunlight. Until now, however, measuring the productivity of subseafloor microbe communities—or how fast they oxidize chemicals and the amount of carbon they produce—has been nearly impossible.

A new study by Woods Hole Oceanographic Institution (WHOI) scientists has unveiled that these microbe-based ecosystems are surprisingly productive and play an important role supporting life higher up the food chain in the food-starved deep ocean. They estimate that worldwide, deep-sea hydrothermal  microbial communities can produce more than 4,000 tons of organic  each day, the building block of life. That is roughly the same amount of carbon in 200 blue whales—making these ecosystems among the ocean’s most productive on a per volume basis. The study appears in the June 11, 2018, issue of Proceedings of the National Academy of Sciences.

“We found that microbial communities living below the seafloor at vents can generate similar amounts of carbon as the well-known animal communities above seafloor, like the tube worms, which are known to be as productive as rainforest ecosystems,” said Stefan Sievert, a microbiologist at WHOI and senior author of the study. “The significant amounts of carbon these organisms produce daily provide an important source of food and energy for other organisms in the deep sea, where there’s generally a lot less carbon available.” As carbon from decomposing marine life sinks from surface waters to the deep, bacteria and other microorganisms chomp away at it until it withers away to marine gristle. “What’s coming down from the surface to these depths isn’t all that much, and not very digestible to deep-sea life,” said Jesse McNichol, who conducted this work as a Ph.D. student at WHOI and is the first author of the study.

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