Characterizing organic carbon at Escanaba Trough

The global ocean is a significant carbon sink, absorbing about a third of all atmospheric carbon dioxide (CO²) emissions (Gruber et al., 2019). Much of that carbon is photosynthesized—that is, converted into organic matter—and may eventually reach the seafloor, where it becomes part of the sediments. Globally, the top one meter (3.3 feet) of the seafloor contains two and a half times as much carbon as all atmospheric CO² (Atwood et al., 2020). However, relatively few studies have looked at organic carbon cycling in deep-sea settings, largely due to the difficulty of conducting research there.

In a new study, USGS researchers characterized carbon-containing compounds in sediments from Escanaba Trough, a hydrothermal system where mineral-rich fluids vent from the seafloor and precipitate, forming active chimneys, inactive sulfide mounds, and hydrocarbon-rich sediments, which can contain metals, critical minerals, and petroleum. The venting fluids also feed chemosynthetic organisms that create energy from hydrothermal chemicals rather than light, giving rise to entire deep-sea ecosystems in the cold, dark depths.