Flounder (Platichthys flesus) muscle as an indicator of metal and organochlorine contamination of French Atlantic coastal waters

Five sets of 18 to 25 flounders each (Platichthys flesus) were collected in four locations in French coastal waters, near the Gironde, Loire and Seine estuaries and western Normandy. Concentrations of metals (Cd, Cu, Pb, Zn, total Hg and CH3Hg), chlorobiphenyls (CBs 28, 52, 101, 118, 153, 138, 180) and pesticides (p,p′-DDT, p,p′-DDD, p,p′-DDE and γHCH) were measured in the muscle tissue from each individual fish. Measurements of fish length, weight and fat content were also performed. No significant difference in length between the five sets was observed; this allows a better comparison of the concentrations of chemical substances between fish sets. Significant differences were observed between locations. High Cd and Zn levels are encountered in the vicinity of the Gironde Estuary where metal contamination has been previously pointed out. As already noticed by the French Mussel Watch Program, the Loire Estuary is contaminated by Pb. Relationships between metals concentrations in the muscle and fish length indicate that mercury is the only metal which accumulates in muscle during the life of the flounder. The highest concentrations of CBs are found in flounders from the Seine Estuary. The differences in concentration between regions are associated with differences in CBs composition. Significant relationships were found between the concentration of certain CBs and length. Highest concentrations of DDT and its degradation products are found in flounders from Seine Estuary. Generally, the geographical distributions of contaminants in the muscle tissue of the flounder agree well with the findings of the French Mussel Watch. This observation shows that flounder muscle is also a valid tool for monitoring chemical contamination in coastal areas.