Dynamics of microbial planktonic food web components during a river flash flood in a Mediterranean coastal lagoon |
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Authors: | David Pecqueur Francesca Vidussi Eric Fouilland Emilie Le Floc’h Sebastien Mas Christian Salles Marie-George Tournoud " target="_blank">Behzad Mostajir |
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Institution: | 1.Laboratoire d’Ecologie des Systèmes Marins c?tiers (ECOSYM), Unité Mixte de recherche (UMR) 5119, Université Montpellier 2, Centre National de la recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Institut fran?ais de recherche pour l’exploitation de la mer (IFREMER),Université Montpellier 1,Montpellier,France;2.ECOSYM,Université Montpellier 2,Montpellier,France;3.Station Méditerranéenne de l’Environnement Littoral, ECOSYM,Sète,France;4.Centre d’écologie marine expérimentale MEDIMEER (Mediterranean center for Marine Ecosystem Experimental Research), UMS 3301,Université Montpellier 2, Centre National de la recherche Scientifique (CNRS),Montpellier,France;5.Station Méditerranéenne de l’Environnement Littoral, MEDIMEER,Sète,France;6.Hydrosciences, UMR 5569 CNRS,Université Montpellier 2, IRD,Montpellier,France;7.Maison des Sciences de l’Eau,Montpellier Cedex 5,France |
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Abstract: | Episodic river flash floods, characteristic of Mediterranean climates, are suspected to greatly affect the functioning of
microbial food webs. For the first time, the abundance, biomass and diversities of microbial food web components were studied
before and during 4 consecutive days after a flash flood that occurred in November 2008, in the surface waters of five stations
along a salinity gradient from 20 to 36 in the Thau lagoon. Eukaryotic pico- and nanophytoplankton were discharged from the
river into the lagoon and increased by 30- and 70-fold, respectively. Bacteria increased by only 2-fold in the lagoon, from
around 4–8 × 106 cells ml−1, probably benefiting from river nutrient input. Chlorophyll a increased 4-fold, and pigment biomarkers showed that the dinophyceae, prasinophyceae and prymnesiophyceae were sensitive
to the flood perturbation, whereas the bacillariophyceae, cryptophyceae and chlorophyceae were resistant and/or transported
to the lagoon from the river. Predator responses were more complex as total heterotrophic flagellate abundance decreased slightly,
whereas those of specific naked ciliates increased, particularly for Uronema sp. The flood also induced a specific change in diversity, from a community dominated by Strobilidium spiralis to a community dominated by Uronema sp. The tintinnid community was particularly sensitive to the flood event as the abundance of all species decreased greatly.
The high increases in biomass, mainly brought by the river during the flood, could have eventually sedimented to the benthic
layer and/or been transported further into the lagoon, supporting the pelagic food web, or have even been exported to the
Mediterranean Sea. |
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