Global patterns and drivers of C:N:P in marine ecosystems

Abstract The coupling between oceanic carbon-nitrogen-phosphorus (CNP) cycles is a fundamental component of ocean ecosystems. It is now widely recognized that CNP stoichiometry of marine ecosystems is variable through space and time. However, several competing hypotheses have been proposed invoking unique biochemical mechanism and associated environmental drivers to describe the observed patterns. We here quantified the detailed hydrography, plankton genomic diversity, and particulate organic matter to understand the global biogeography of ecosystem CNP stoichiometry across 1370 stations as part of Bio-GO-SHIP. We observed clear latitudinal variability in CNP and show that surface temperature is responsible for much of the stoichiometric variability at high latitudes. Genomic observations allowed us to separate each elemental stress type and revealed that the interaction between nutrient supply rate and N vs. P stress is critical for hemispheric and regional CNP variability. Future climate projections suggest that C:P and N:P ratios will increase at high latitudes, but changes are highly uncertain at low latitudes due to a lack of observations at extreme surface ocean temperature and possible shifts in N vs. P stress. Our observations suggest a systematic regulation of elemental stoichiometry among ocean ecosystems, but future changes are highly uncertain.