Résumé
In shallow human-impacted systems, sediment resuspension events can result in pulsed exposures of pelagic organisms to multiple contaminants. Here, we examined the impact of the resuspension of contaminated sediment on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea), by conducting an in situ microcosm experiment over a 96-h period. Natural phytoplankton was exposed to elutriates prepared from a contaminated-sediment resuspension simulating process, and its functional and structural responses were compared with those of non-exposed phytoplankton. The elutriates displayed moderate multiple contamination by trace metals and PAHs. Our results show that elutriate exposure induced both functional and structural phytoplankton changes. Elutriates strongly stimulated phytoplankton growth after 24 h of exposure. They also enhanced phytoplankton photosynthetic performance during the first hours of exposure (up to 48 h), before reducing it toward the end of the experiment. Elutriates were also found to slightly stimulate Bacillariophyceae and conversely to slightly inhibit Dinophyceae in the short term. Additionally, they were found to stimulate phycocyanin-rich picocyanobacteria in the short term (8-48 h) before inhibiting it in the longer term (72-96 h), and to inhibit eukaryotic nanophytoplankton in the short term (8-48 h) before stimulating it in the longer term (72-96 h). Sediment resuspensions are thus likely to have significant effects on the global dynamics and functions of phytoplankton in contaminated coastal environments.