Genomic evidence for global ocean plankton biogeography shaped by large-scale current systems

Abstract : Biogeographical studies have traditionally focused on readily visible organisms, but recent technological advances are enabling analyses of the large-scale distribution of microscopic organisms, whose biogeographical patterns have long been debated1,2. The most prominent global biogeography of marine plankton was derived by Longhurst3 based on parameters principally associated with photosynthetic plankton. Localized studies of selected plankton taxa or specific organismal sizes1,4–7 have mapped community structure and begun to assess the roles of environment and ocean current transport in shaping these patterns2,8. Here we assess global plankton biogeography and its relation to the biological, chemical and physical context of the ocean (the ‘seascape’) by analyzing 24 terabases of metagenomic sequence data and 739 million metabarcodes from the Tara Oceans expedition in light of environmental data and simulated ocean current transport. In addition to significant local heterogeneity, viral, prokaryotic and eukaryotic plankton communities all display near steady-state, large-scale, size-dependent biogeographical patterns. Correlation analyses between plankto transport time and metagenomic or environmental dissimilarity reveal the existence of basin-scale biological and environmental continua emerging within the main current systems. Across oceans, there is a measurable, continuous change within communities and environmental factors up to an average of 1.5 years of travel time. Modulation of plankton communities during transport varies with organismal size, such that the distribution of smaller plankton best matches Longhurst biogeochemical provinces, whereas larger plankton group into larger provinces. Together these findings provide an integrated framework to interpret plankton community organization in its physico-chemical context, paving the way to a better understanding of oceanic ecosystem functioning in a changing global environment.