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 length 3 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.

Plasticity of European flounder life history patterns discloses alternatives to catadromy

“…Although no other studies have definitively shown that the species exhibits this behavior, it is widely accepted (e.g. Borsa et al 1997, Minier et al 2000, Marchand et al 2003, Franco et al 2008. However, there has been no broad-scale, multi-site study showing the existence of a generalized catadromous strategy across the entire distribution range of the species.…”

“…However, there is still controversy about classifying flounder as catadromic, semi-catadromic, estuarine migrant, marine-estuarine opportunistic (Elliott et al 2007) or even as a truly estuarine resident species (Elliott & Dewailly 1995). Recent works clearly proved that flounder is not an estuarine resident species (Daverat et al 2011, Morais et al 2011, although field observations confirmed that flounder use estuarine habitats (Jager 1999, Marchand et al 2003 as well as freshwater habitats for extended periods (Radforth 1940, Beaumont & Mann 1984. Indeed, freshwater was found to trigger the metamorphosis of flounder (Hutchinson & Hawkins 2004), and larvae are able to migrate upstream efficiently to their estuarine nursery ground using selective tidal transport (Bos 1999).…”

Population Genetic Structure of the Spotted Wolffish, Anarhichas minor, in the North Atlantic

“…In particular these samples show substantial differences in allele frequencies at two of the three allozymes (IDPH and MDH-3). Thus, given the fact that allozymes might be sensitive to selection (Marchand MEPS 2003) [22], we can suppose that the genetic variability of the Norwegian broodstock has been shaped by substantial selective pressures induced by hatchery practices, but that is only seen in the allozyme data due to possible selection on these markers.…”

“…One explanation of this might be linked to low population size of spotted wolffish in the Gulf of St. Lawrence, but two other hypotheses are possible: (1) the mixture in the same sample of individuals stemming from genetically differentiated units (Walhund effect) or (2) selection processes. It is important to keep in mind that allozymes can be submitted to strong selective pressure (Merchand MEPS 2003) [22]. Random genetic drift may also cause a sudden increase in rare alleles (Falconer IQG 1989) [28].…”

Trace metals (Cu, Zn, Cd and Pb) in juvenile fish from estuarine nurseries along the Portuguese coast

“…chromium, nickel, silver, mercury, arsenic and selenium) are persistent in aquatic environments and are likely to occur in increased concentrations due to anthropogenic actions (Neff, 2002). Moreover, metals are of great interest as they can result in direct energetic and physiological costs, expressed in decreased growth and low physiological condition, as well as indirect costs due to the many defence mechanisms triggered (Livingstone, 2001;Marchand et al, 2003;van der Oost et al, 2003;Fonseca et al, 2009).…”