Search for impact of a dredged material disposal site on growth and metal contamination of Mytilus edulis (L.) in charente-maritime (France)

Transplanted mussels, Mytilus edulis (L.), were used as bioindicators to assess the metal contamination and biological effects of the dredging activities in the harbour of La Rochelle-La Pallice which result in the dumping of sediment in the site of the ‘Le Lavardin’ located in the vicinity of two economically important shellfish farming zones. Immersion of dredged material appeared to have no influence on the growth of mussels within their first year of development, when compared to the size of individuals sampled from neighbouring farming zones (40 mm). The Dry Condition Indexes calculated from individuals present in the disposal site were similar to those found in mussels sampled from a natural population. After three months of immersion around the disposal site, copper and zinc concentrations were similar to those recorded in individuals from a natural population. In contrast, the cadmium concentration was lower. Mussels from the northern stations of the site exhibited lead contamination. However, the respective roles of both dredged material and coastal inputs in the disposal site could not be distinguished.