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Tiny organisms’ race to the bottom of the ocean

Paper: Microbial dynamics of elevated carbon flux in the open ocean’s abyss

Authors: Kirsten Poff, Andy Leu, John Eppley, David Karl and Edward DeLong

Cells from blooms of phytoplankton, or tiny plants, can enhance carbon flux all the way down to the deepest parts of the ocean. The authors of this recent study measured the amount of carbon in sinking particles deep in the ocean at a station near Hawaii. Over the course of three years, scientists identified three time periods of unusually high carbon flux, or transport, at this depth, and found that the organisms that made up the sinking particles were significantly different between high flux events and the rest of the time period. The data showed higher abundances of surface-dwelling microorganisms, including phytoplankton, contributing to these particles during high-flux events.

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Antarctic krill and their role in ocean carbon cycling

Antarctic Krill under a microscope. Photo courtesy of Uwe Kils, CC-BY-SA 3.0

Paper: Manno et al. (2020)

The transfer of carbon from the surface ocean to the deep ocean, or carbon export, can strongly influence climate. The main pathway of carbon export in the ocean is through sinking particles, also known as the biological carbon pump. These sinking particles can include plankton biomass, aggregates of cells, and zooplankton feces and molts. Understanding what contributes to carbon export is important in understanding how this may change as temperatures warm due to climate change.

A recent study by Manno et al. found that Antarctic krill in the Southern Ocean may play a significant role in transporting carbon to the deep ocean through their carcasses, fecal material, and most notably their molts, or shedding of their shells. Exoskeletons are not only an important vehicle for carbon export but also provide food to animals living on the seafloor. This is the first study to investigate the contribution of krill molts to carbon export in the Southern Ocean.

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