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Résumé :
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The Mediterranean lagoon of La Palme was studied from October 1994 to December 1998. Approximately 230 surveys were made with over 15,000 measurements of physico-chemical parameters (temperature, pH, dissolved oxygen, oxygen saturation, salinity, conductivity, redox potential and tributaries water flow). Approximately 400 chemical analyses of the main nutrients as well as more than 1,000 observations on flora, fauna and sediment were made. The La Palme lagoon was found to be one of the rare oligotrophic Mediterranean lagoons with very good water quality. The measured parameters were found to follow a well-defined seasonal rhythm in spite of large absolute variations and inter-annual differences. In spite of heavy transformations in the last century, the catchment area as well as the entrance channel to the open sea remain relatively natural. Special observations on the karstic springs show that they have great influence on the water balance. Via the catchment area meteorological conditions directly and indirectly influence strongly the conditions inside the lagoon. The exchange with the open sea buffers the extreme amplitude of abiotic parameters inside the lagoon but the lagoon "character" seems to be determined by sediment and nutrient input from the catchment area. The Etang de La Palme could serve as an excellent example of spatio-temporal dynamics inside undisturbed oligotrophic coastal lagoons.
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