Institut de Biologie de l'École Normale Supérieure ENS . CNRS UMR8197 . Inserm U1024 Directeur : Pierre Paoletti

In Brief

The drivers of ocean plankton diversity across archaea, bacteria, eukaryotes, and major virus clades are inferred from both molecular and imaging data acquired by the Tara Oceans project and used to predict the effects of severe warming of the surface ocean on this critical ecosystem by the end of the 21st century.

Highlights

• Most epipelagic planktonic groups exhibit a poleward decline of diversity
• No latitudinal diversity gradient was observed below the photic zone
• Temperature emerges as the best predictor of epipelagic plankton diversity
• Global warming may increase plankton diversity, particularly at high latitudes

Summary

The ocean is home to myriad small planktonic organisms that underpin the functioning of marine ecosystems. However, their spatial patterns of diversity and the underlying drivers remain poorly known, precluding projections of their responses to global changes. Here we investigate the latitudinal gradients and global predictors of plankton diversity across archaea, bacteria, eukaryotes, and major virus clades using both molecular and imaging data from Tara Oceans. We show a decline of diversity for most planktonic groups toward the poles, mainly Q9 driven by decreasing ocean temperatures. Projections into the future suggest that severe warming of the surface ocean by the end of the 21st century could lead to tropicalization of the diversity of most planktonic groups in temperate and polar regions.
These changes may have multiple consequences for marine ecosystem functioning and services and are expected to be particularly significant in key areas for carbon sequestration, fisheries, and marine conservation.

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Photo : © Christian & Noé Sardet / Tara Ocean Foundation