Organic matter respiration stoichiometry in the Arctic Ocean is linked to shifts in plankton community composition

Abstract

The global rate of ocean deoxygenation may be influenced by the molar ratio of dissolved oxygen to organic carbon consumed during microbial respiration. However, respiration stoichiometry and its environmental controls are not fully understood due to sparse direct measurements and limited global coverage. Here, we measured surface concentrations of particulate chemical oxygen demand, particulate organic carbon, and particulate organic nitrogen from the Bering Sea (54°N) to the North Pole (90°N). Unlike previous measurements in other regions, the respiration quotient (−O 2 :C) was not primarily associated with sea surface temperature or nitrate availability. Instead, it was more strongly correlated with sea surface salinity, with oxygen isotope measurements (δ 18 O) supporting sea ice formation as a contributor to salinity variability. Based on DNA sampling and short‐read metagenomic sequencing, we found that the relative abundance of heterotrophic bacteria positively correlated with sea surface salinity and the respiration quotient. Additionally, gene modules involved in nitrogen metabolism and lipid synthesis were relatively more common when the respiration quotient was higher. These results suggest that Arctic respiration stoichiometry is linked to shifts in plankton community composition, which may help constrain projections of oxygen demand in a warming ocean.

Bibliographic Information