Genomic-to-space measurements reveal large-scale ocean nutrient stress

Global ocean phytoplankton growth and primary production are intimately
linked to nutrient fluctuations from seasonal to millennial time scales.
Rapid recycling compromises the utility of surface nutrient or
phytoplankton stocks for delineating the biogeography of global ocean
nutrient stress. Here, field-measured hydrography and ‘omics biomarkers of
nutritional status are coupled to a satellite remote sensing metric of
cell physiology to mechanistically evaluate monthly to multi-decadal
shifts in global phytoplankton nutrient stress. We observe a clear
biogeography in nutrient stress aligned with variations in the nutricline
depth and distinctly elevated stress in nitrogen- compared to
phosphate-limited waters. Regions where cells are switching to rare forms
of alternative nutrients are most stressed. Temporal modes of stress are
dominated by seasonal changes, but strong signatures of natural climate
cycles are also apparent. Surface ocean warming over the last twenty years
has led to broad increases in nutrient stress with one notable exception.
Southern hemisphere oligotrophic regions experienced declines in nutrient
stress that we attribute to changes in ocean nitrogen fixation. Our
integrated hydrography, genomic, and satellite remote sensing of
phytoplankton physiology has uncovered contemporary changes in global
phytoplankton nutrient stress.