Chemical contamination alters the interactions between bacteria and phytoplankton

Olivier Pringault (1) , Marc Bouvy (2) , Claire Carré (2) , Kaouther Mejri , Chrystelle Bancon-Montigny (3) , Catherine Gonzalez (4, 5) , Christophe Leboulanger (2) , Asma Sakka Hlaili , Marisol Goñi (6)

1 IRD - Institut de Recherche pour le Développement
2 UMR MARBEC - MARine Biodiversity Exploitation and Conservation
3 PEnSTer - PEnSTer: Pollutions Environnement Santé Territoire
4 ERT - IMT Mines Alès - ERT
5 CONTEM - CONTEM: Contaminats Emergents
6 IPREM - Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux

Bacteria and phytoplankton are key players in aquatic ecosystem functioning. Their interactions mediate carbon transfer through the trophic web. Chemical contamination can alter the function and diversity of phytoplankton and bacterioplankton, with important consequences for ecosystem functioning. The aim of the present study was to assess the impact of chemical contamination on the interactions between both biological compartments. Two contrasting marine coastal ecosystems, offshore waters and lagoon waters, were exposed to chemical contamination (artificial or produced from resuspension of contaminated sediment) in microcosms in four seasons characterized by distinct phytoplankton communities. Offshore waters were characterized by a complex phytoplankton–bacterioplankton network with a predominance of positive interactions between both compartments, especially with Haptophyta, Cryptophyta, and dinoflagellates. In contrast, for lagoon waters, the phytoplankton–bacterioplankton network was simpler with a prevalence of negative interactions with Ochrophyta, Cryptophyta, and flagellates. Contamination with an artificial mix of pesticides and trace metal elements resulted in a decrease in the number of interactions between phytoplankton and bacterioplankton, especially for offshore waters. Resuspension of contaminated sediment also altered the interactions between both compartments. The release of nutrients stored in the sediment allowed the growth of nutrient limited phytoplankton species with marked consequences for the interactions with bacterioplankton, with a predominance of positive interactions, whereas in lagoon waters, negative interactions were mostly observed. Overall, this study showed that chemical contamination and sediment resuspension resulted in significant effects on phytoplankton–bacterioplankton interactions that can alter the functioning of anthropogenic coastal ecosystems

Domaines: Biodiversité et Ecologie

Olivier Pringault, Marc Bouvy, Claire Carré, Kaouther Mejri, Chrystelle Bancon-Montigny, et al.. Chemical contamination alters the interactions between bacteria and phytoplankton. Chemosphere, 2021, 278, pp.130457. ⟨10.1016/j.chemosphere.2021.130457⟩. ⟨hal-03369101⟩