Responses of European flounder Platichthys flesus populations to contamination in different estuaries along the Atlantic coast of France

Abstract

Genetic and physiological responses of flounder Platichthys flesus populations to chemical stress were investigated in 3 highly contaminated French estuaries (the Vilaine, Loire and Gironde) and compared to those observed in the Ster estuary, considered as a reference site because of its reletively low level of contamination. In the Vilaine, Loire and Gironde populations, multi-loci heterozygosity (allozymes: PGM, GPI-2, MPI, IDHP, AAT-1, AAT-2) was lower than in the reference site. The mean growth rate was measured by back-calculation from otoliths, and the mean condition factor corresponded to the somatic weight:fish length3 ratio. The fish from contaminated estuaries displayed lower values for both parameters than those from the Ster. Among the alleles, PGM 85, AAT-1 95, and to a lesser extent MPI 90, MPI 95 and IDHP 90, could be considered as 'resistant' to contamination. In contaminated estuaries, these alleles were carried by individuals that displayed good fitness, measured as high DNA integrity (low coefficient of variation of DNA content in blood cells) by flow cytometry. The frequencies of these alleles were also more elevated compared to fish from the reference site. Moreover, the comparative analysis of the relationships between genotypic and phenotypic responses of flounder populations to pollution in the 4 studied estuaries highlighted some specificity in relation to contamination typology.