Differences in physiology explain succession of mixoplankton functional types and affect carbon fluxes in temperate seas

• Published in: Progress in oceanography Vol. 190; p. 102481
• Main Authors: Leles, Suzana Gonçalves, Bruggeman, Jorn, Polimene, Luca, Blackford, Jerry, Flynn, Kevin J, Mitra, Aditee
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-01-2021
• Subjects: Carbon cycling; Ecological model; Ecosystem functioning; Mixotrophy; Plankton; Protists; Seasonal succession; Protists; Plankton; Seasonal succession; Mixotrophy; Carbon cycling; Ecosystem functioning; Ecological model
• ISSN: 0079-6611; 1873-4472
• DOI: 10.1016/j.pocean.2020.102481

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•Mixoplankton functional types (MFTs) have different seasonal patterns.•Functional differences affect the diverse roles of mixoplankton in carbon fluxes.•MFTs differ based on whether they possess or acquire photosystems and cell size.•Model results show the importance of mixotrophy both during summer and late winter conditions.
Different hypotheses have been proposed explaining plankton community assembly and how changes in biodiversity can impact ecosystem function. Mixoplankton (photo-phago-trophs) are important members of the plankton, butscience lacks a clear understanding of their role in plankton succession. Here, we used a modelling approach to evaluate the seasonalities of mixoplankton functional types (MFTs) and to test the hypothesis that functional differences affect their roles in key carbon fluxes. Functional differences were modelled based on cell size and whether mixoplankton possess their own, or acquire, photosystems. Ecosystem simulations incorporated realistic environmental variability and were validated against a 9 yr long-term time series of nutrients, chlorophyll-a, and plankton data from a coastal temperate sea. Simulations, consistent with empirical data, show that mixoplankton of different sizes are present throughout the water column and over time, with seasonal population dynamics differing among the different MFTs. Importantly, the partitioning of production among different size-classes depends on how mixoplankton functional diversity is described in the model, and that merging mixoplankton into one functional type can mask their diverse ecological roles in carbon cycling. Mixoplankton thus play an important role in structuring the plankton community and its dynamics in the simulations.