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Approche multi-taxonomique des communautés aquatiques dans le lac de Lacanau

Abstract : In lake ecosystems, biological taxa are usually studied either through trophic relationships (without considering environmental factors) or distinctly for each taxonomical group. In the last case, studying the response of communities to environmental abiotic factors is usually the main objective and biotic interactions are therefore rarely considered. This is the objective of the present study which aims to investigate, synchronously, the response of different biological taxa in the Lacanau's lake (South-West of France) to abiotic and biotic factors. More precisely, the effect of season, spatial variation, physico-chemical parameters and physical factors (e.g. wind, slope) on macrophytes, phytoplankton, epiphytic diatoms and micro-meiofauna communities and biomass will be tested. The aim is also to construct global models of the ecosystem to determine the relative effect of environmental factors and biotic relationships. At the same time, another goal is to investigate, for the first time, epiphytic micro-meiofauna taxa living in Lacanau's lake. We thus studied 6 stations located around the littoral shoreline that were sampled during the four temperate seasons. Permanent plots (24 per station) were installed to study macrophyte composition and phytoplankton biomass. Water samples were taken (3 per station) and water composition was analyzed through more than 20 parameters. Five macrophytes species were also sampled in each station to measure the composition and biomass of the epiphytic flora and fauna. Results revealed a strong seasonal variation of water composition. Taxa did not exhibit a synchronic response through time and, within taxa group, we often evidenced different variation of diversity and biomass with time. Microscopic organisms appeared to be strongly dependent of seasonal variation but it was almost impossible to separate the influence of physico-chemical parameters from those of seasonal succession. Weak influence of physico-chemical parameters on macrophytes communities was found (except for biomass) but these communities strongly depends on hydrodynamical and hydromorphological conditions. Physical factors also appeared to strongly impact phytoplankton diversity and biomass. Nature and architecture of plant host was found to greatly influence the biomass and diversity of diatoms and micro-meiofauna epiphytic communities. Considering biotic relationships, competition processes with macrophytes species seems to structure phytoplankton communities and the micro-meiofauna biomass and diversity appeared to be controlled by epiphytic diatoms. All these processes were correctly modeled in final models which allowed to test the relative influence of chemical, physical and biological factors. This fundamental study bring better knowledge on processes patterning biological communities in the Lacanau's lake and also contribute to a better understanding of the whole functioning of this lacustrine ecosystem. Some scientific and management perspectives were drawn from these results, but supplementary studies are still needed to better understand mechanisms patterning these biological communities.
Mots-clés : LACANAU
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https://hal.inrae.fr/hal-02609713
Contributor : Migration Irstea Publications <>
Submitted on : Tuesday, March 2, 2021 - 9:17:59 AM
Last modification on : Friday, April 30, 2021 - 2:34:02 PM

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  • HAL Id : hal-02609713, version 1
  • IRSTEA : PUB00062096

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Aurélien Jamoneau, Vincent Bertrin, Brigitte Delest, Mélissa Eon, Kewin Gery, et al.. Approche multi-taxonomique des communautés aquatiques dans le lac de Lacanau. [Rapport de recherche] Irstea. 2019, pp.167. ⟨hal-02609713⟩

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