Résumé
The accumulation of nutrients, with its short or long term consequences (eutrophication, dystrophic crisis), is a major problem in coastal lagoons. During 1990 a study was carried out at three sampling sites in two coastal lagoons near Montpellier in order to estimate the quantities present and the exchanges between compartments: variables were measured simultaneously in the overlying water, the interstitial water and the sediments. Monthly analyses of the overlying water (temperature, salinity, dissolved oxygen, orthophosphate, ammonium, nitrate and chlorophyll a) allow a general understanding of the functioning of these lagoons and a characterization of each site. The orthophosphate concentration is distinctly higher in summer.