Restructuring of plankton genomic biogeography in the surface ocean under climate change

The impact of climate change on diversity, functioning and biogeography of marine plankton remains a major unresolved issue. Here environmental niches are evidenced for plankton communities at the genomic scale for six size fractions from viruses to meso-zooplankton. The spatial extrapolation of these niches portrays ocean partitionings south of 60 degrees N into climato-genomic provinces characterized by signature genomes. By 2090, under the RCP8.5 future climate scenario, provinces are reorganized over half of the ocean area considered, and almost all provinces are displaced poleward. Particularly, tropical provinces expand at the expense of temperate ones. Sea surface temperature is identified as the main driver of changes (50%), followed by phosphate (11%) and salinity (10%). Compositional shifts among key planktonic groups suggest impacts on the nitrogen and carbon cycles. Provinces are linked to estimates of carbon export fluxes which are projected to decrease, on average, by 4% in response to biogeographical restructuring. The authors define the global environmental niches of plankton from nano- (viruses) to meso-zooplankton (small metazoans) using metagenomic data. They assess reorganizations under climate change and the environmental drivers of change, with focus on the impacts on nitrogen and carbon fluxes.