title: Water flux management and phytoplankton communities in a Mediterranean coastal lagoon. Part II: Mixotrophy of dinoflagellates as an adaptive strategy?
abstract: Dinoflagellate proliferation is common in coastal waters, and trophic strategies are often advanced to explain the success of these organisms. The Biguglia lagoon is a Mediterranean brackish ecosystem where eutrophication has long been an issue, and where dominance of dinoflagellates has persisted for several years. Monthly monitoring of fluorescence-based properties of phytoplankton communities carried out in 2010 suggested that photosynthesis alone could not support the observed situation all year round. Contrasting food webs developed depending on the hydrological season, with a gradual shift from autotrophy to heterotrophy. Progressively, microphytoplankton assemblages became unequivocally dominated by a Prorocentrum minimum bloom, which exhibited very weak effective photosynthetic performance, whereas paradoxically its theoretical capacities remained fully operational. Different environmental hypotheses explaining this discrepancy were examined, but rejected. We conclude that P. minimum bloom persistence is sustained by mixotrophic strategies, with complex compromises between phototrophy and phagotrophy, as evidenced by fluorescence-based observations.
authors.affiliation: UMR MARBEC, IRD - CNRS - Ifremer - University of Montpellier, CC093, 34095 Montpellier Cedex 5, France. Electronic address: Philippe.Cecchi@ird.fr.
authors.forename: P
authors.initials: P
authors.lastname: Cecchi
authors.affiliation: UMR 6134 CNRS Sciences for the Environment, UMS 3514 CNRS, Stella Mare, University of Corsica, BP 52, 20250 Corte, France. Electronic address: Marie.Garrido@oec.fr.
authors.forename: M
authors.initials: M
authors.lastname: Garrido
authors.affiliation: UMR MARBEC, IRD - CNRS - Ifremer - University of Montpellier, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Collos
authors.affiliation: UMR 6134 CNRS Sciences for the Environment, UMS 3514 CNRS, Stella Mare, University of Corsica, BP 52, 20250 Corte, France. Electronic address: pasquali@univ-corse.fr.
authors.forename: V
authors.initials: V
authors.lastname: Pasqualini
mesh_terms: D000222:Adaptation, Physiological; D004141:Dinoflagellida / Q000254:growth & development* / Q000502:physiology; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D005068:Eutrophication; D020387:Food Chain; D005602:France; D052836:Heterotrophic Processes / Q000502:physiology; D008522:Mediterranean Sea; D010788:Photosynthesis / Q000502:physiology; D010839:Phytoplankton / Q000254:growth & development* / Q000502:physiology; D012621:Seasons; D012623:Seawater / Q000737:chemistry*; D014872:Water Movements
keywords: Biguglia; Mediterranean coastal lagoon; Mixotrophy; Phyto-PAM; Phytoplankton; Prorocentrum minimum