1. Benthic diatoms and phytoplankton to assess nutrients in a large lake: Complementarity of their use in Lake Geneva (France–Switzerland)
- Author
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Frédéric Rimet, Bernard Montuelle, Agnès Bouchez, Centre Alpin de Recherche sur les Réseaux Trophiques et Ecosystèmes Limniques (CARRTEL), Institut National de la Recherche Agronomique (INRA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), ANR-11-CESA-0022, and CIPEL (Commission Internationale pour la Protection des Eaux du Leman)
- Subjects
0106 biological sciences ,lake Geneva ,periphyton ,General Decision Sciences ,010501 environmental sciences ,01 natural sciences ,nutrients ,Phytoplankton ,Littoral zone ,bioindicator ,Photic zone ,14. Life underwater ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Ecology ,biology ,010604 marine biology & hydrobiology ,microalgae ,biotic indices ,Pelagic zone ,15. Life on land ,biology.organism_classification ,Diatom ,Habitat ,13. Climate action ,Benthic zone ,[SDE.BE]Environmental Sciences/Biodiversity and Ecology ,Bioindicator - Abstract
International audience; Lakes can be monitored using different bioindicators, among which phytoplankton and benthic diatoms. We compared these two indicators in Lake Geneva for nutrient assessment. Bimonthly samplings were carried out during one year in the euphotic layer of a pelagic site. In the same time four littoral sites were sampled at 40-50 cm depth. Species compositions and abundances of both bioindicators were analyzed following European standards. Water physico-chemical composition was analyzed at the same time. Seasonal succession of benthic diatom guilds was observed. The dynamics of benthic diatom communities were better correlated to the pelagic chemistry than to the local littoral chemistry. We also observed that in the sampling sites frequently exposed to winds and waves, benthic diatoms showed lower correlations to physico-chemical dynamics, because of an increase of pioneer diatoms abundance adapted to turbulent environment, such sites must be avoided for lake monitoring. Finally, biotic indices calculated with benthic diatoms in wind protected sites showed higher correlations with pelagic nutrient concentration (PO43-) than indices calculated with phytoplankton. This unexpected situation can be explained by differences of temporal variability of chemical and biological compartments. Littoral chemistry changed faster than pelagic chemistry because of rains, diffuse flow from watershed and rivers flowing in the littoral zone whereas pelagic chemistry has a much smoother evolution because it is situated 10 km from the coast. But phytoplankton showed a high temporal variability because of wind influence, which explained the low correlation with the smooth evolution of pelagic chemistry. On the other hand, benthic diatoms from sites protected from the dominant wind, showed a lower temporal variability and were more in synchrony with the smooth evolution of pelagic chemistry. Even if we show that diatom seem to be promising indicator of nutrient level of the lake, we also underline the complementarity of using both indicators: benthic diatom and phytoplankton. Each of them brings different information about temporal variability of the lake and about the functioning of different habitats. Comparing these two bioindicators only on the basis of nutrient correlation ability would be an over-simplification whom managers must be warned.
- Published
- 2015
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