Comprehensive Model of Annual Plankton Succession Based on the Whole-Plankton Time Series Approach

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Comprehensive Model of Annual Plankton Succession Based on the Whole-Plankton Time Series Approach

Jean-Baptiste Romagnan 1,2 *, Louis Legendre 1,2 , Lionel Guidi 1,2 , Jean-Louis Jamet 5 , Dominique Jamet 5 , Laure Mousseau 1,2 , Maria-Luiza Pedrotti 1,2 , Marc Picheral 1,2 , Gabriel Gorsky 1,2 , Christian Sardet 3,4 , Lars Stemmann 1,2

1 Sorbonne Universités, UPMC Univ Paris 06, UMR 7093 LOV, F-75005, Paris, France, 2 CNRS, UMR 7093 LOV, F-75005, Paris, France, 3 Sorbonne Universités, UPMC Univ Paris 06, UMR 7009 BioDev, F-75005, Paris, France, 4 CNRS, UMR 7009 BioDev, F-75005, Paris, France, 5 Université du Sud Toulon- Var, PROTEE EBMA, 83000, La Garde, France

* romagnan@obs-vlfr.fr

Abstract

Ecological succession provides a widely accepted description of seasonal changes in phy- toplankton and mesozooplankton assemblages in the natural environment, but concurrent changes in smaller (i.e. microbes) and larger (i.e. macroplankton) organisms are not includ- ed in the model because plankton ranging from bacteria to jellies are seldom sampled and analyzed simultaneously. Here we studied, for the first time in the aquatic literature, the suc- cession of marine plankton in the whole-plankton assemblage that spanned 5 orders of magnitude in size from microbes to macroplankton predators (not including fish or fish lar- vae, for which no consistent data were available). Samples were collected in the northwest- ern Mediterranean Sea (Bay of Villefranche) weekly during 10 months. Simultaneously collected samples were analyzed by flow cytometry, inverse microscopy, FlowCam, and ZooScan. The whole-plankton assemblage underwent sharp reorganizations that corre- sponded to bottom-up events of vertical mixing in the water-column, and its development was top-down controlled by large gelatinous filter feeders and predators. Based on the re- sults provided by our novel whole-plankton assemblage approach, we propose a new com- prehensive conceptual model of the annual plankton succession (i.e. whole plankton model) characterized by both stepwise stacking of four broad trophic communities from early spring through summer, which is a new concept, and progressive replacement of eco- logical plankton categories within the different trophic communities, as recognised traditionally.

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