AbstractThe impact of climate change on diversity, functioning and biogeography of marine plankton remains a major unresolved issue. Here, niche theory is applied to plankton metagenomes of 6 size fractions, from viruses to meso-zooplankton, sampled during theTaraOceans expedition. Niches are used to derive plankton size-dependent structuring of the oceans south of 60°N inclimato-genomicprovinces characterized by signature genomes. By 2090, assuming the RCP8.5 high warming scenario, provinces would be reorganized over half of the considered ocean area and quasi-systematically displaced poleward. Particularly, tropical provinces would 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.