Ecological interpretation of metal contents and contaminant source characterisation of sediments from a megatidal estuary.

Sediments and the associated biota constitute an important compartment in the biogeochemical cycle of trace metals in soft substrate megatidal estuaries. The relationship between physicochemical, ecological properties, metal concentrations determined in megatidal estuary sediments from the French coast of the English Channel, the Baie des Veys and the macrobenthic organisms, are analysed, interpreted and reported. Total concentrations of zinc, cadmium, lead and copper were measured in mudflats and saltmarsh sediments using Differential Pulse Voltammetry. Sediment characteristics were obtained by measurement of particle size, water content, total organic carbon and carbonate content, using AFNOR standards. A semi-quantitative scale was used for assessing the density of the macrobenthic flora and fauna at each sampling site. Analysis of data obtained from this study showed a correlation between the concentrations of monitored trace metals and species of the macrobenthic fauna. The results of this study show that the physico-chemical characteristics of the sediments affect the retention of metals in the sediment and this in turn affects the biota.

[Intertidal macrozoobenthos evolution of the "Baie des Veys' between 1985 and 2000]. / Evolution du macrozoobenthos intertidal de la baie des Veys de 1985 a 2000.

Intertidal macrozoobenthos evolution of the 'Baie des Veys' between 1985 and 2000. The distribution of intertidal macrozoobenthos in the 'Baie des Veys' (French coast of the eastern English Channel) has been studied in 2000. Results were compared with those of 1985, which are included in a long-term monitoring program established since 1973. The populations remained distributed along an estuarine-marine gradient, with a particularity on the eastern side, which is isolated from the rest of the bay by a river channel. The western and central tidal flats became more subjected by marine influence, which led to a homogenisation of the benthic communities. Oyster farming locally caused a fast decrease of the typical eastern community, which was characterized by Scoloplos armiger and Urothoe poseidonis.