Calanus Copepods Are as Important as Marine Snow in Arctic Vertical Carbon Flux

Abstract

The vertical transport and storage of atmospheric carbon through the biological carbon pump (BCP) follows multiple pathways. The lipid pump is a recently recognized BCP process driven by the seasonal vertical migration of copepods utilizing carbon‐rich lipid reserves during extended overwintering periods at depth where they release carbon through respiration and mortality. Previous estimates for the Arctic suggest that the lipid pump carbon (LPC) flux exports similar amounts of carbon as the sinking particulate organic carbon (POC) in the gravity pump. However, concurrent sampling is necessary for accurate comparisons between the BCP pathways. Here, we used in situ imaging to simultaneously observe the distributions of Calanus copepods and marine snow within seven Arctic subregions. The calculated LPC flux ranged from 0.77 to 4.15 g C m ⁻²  y ⁻¹ which was comparable to the range of POC flux estimates, confirming the importance of the lipid pump in Arctic vertical carbon flux. We found that average LPC flux is double that of POC flux in deep basin subregions, implying that deep habitats where diapausing copepods reside are critical for Arctic carbon storage. This study provides a foundation for improved understanding of the BCP pathways in a changing Arctic and offers methodological advancements for expanding the monitoring of the lipid pump.