Fig 1.
Integrative approach undertaken in this study to assess short- and long-term effects of a chronic chemical contamination on natural populations of the marine bivalve Mimachlamys varia.
Photo credit: Thierry Guyot.
Fig 2.
Location of the four sampling areas along the French Atlantic coast: Loix-en-Ré (Ré Island), Les Minimes (near sailing harbour), Port-Neuf (near water treatment of La Rochelle), Les Palles (near the mouth of the Charente estuary).
Fig 3.
Photo showing the anatomy of the scallop Mimachlamys varia with (A) soft parts inside of the shell (digestive gland, adductor muscle, gills and mantle) and (B) outside of the shell.
Photo credit: Thierry Guyot.
Table 1.
Summary of our sampling design.
Analyses of two types of chemical contaminants (trace metals and organic pollutants), biomarkers, phosphatases and genetic data were conducted on natural populations of variegated scallops (Mimachlamys varia) sampled at four sites. Analyses listed under the same “Analysis group” were conducted on the same variegated scallop individuals. All analyses but one were performed for each individual (sample size per site is shown in parentheses). The remaining analysis was conducted on a pool of 10 individuals per site. The type of tissue that was analyzed is indicated in the last column.
Table 2.
Trace element concentrations (μg/g of dry weight) in the digestive glands of Mimachlamys varia (7<n<10 per sites) from the four sampling areas (Loix-en-Ré, Minimes, Port-Neuf, Les Palles) in March 2014 and in September 2014.
Table 3.
Organic contaminants concentrations (μg/kg of dry weight) in the digestive glands of Mimachlamys varia (5<n<10 per sites) from the four sampling areas (Loix-en-Ré, Minimes, Port-Neuf, Les Palles) in March 2014 and in September 2014.
Fig 4.
Biomarkers and phosphatase activity assessed in the final fraction of Mimachlamys varia digestive glands or muscle (see Material and Methods) for March and September 2014 from Loix-en-Ré (Loix), Les Minimes (MIN), Port-Neuf (PN) and Les Palles (LP).
CS: Citrate synthase activity, MDA: MDA contents, SOD: SOD activity, GST: GST activity, LAC: Laccase activity. Note that the barplot for phosphatase activity is separated by a frame as this activity was measured using 10 pooled individuals (see Material and Methods). Sampling seasons (March and September) are color-coded and are shown on the same barplot. Values represent mean ± standard error (n = 10 individuals per site for biomarkers; n = 3 replicate measurements of the pool for Phosphatase activity). Within each season, bars that do not differ significantly (p > 0.05) share the same letters. No letters are shown above bars when there was no significant statistical difference among sites.
Fig 5.
Canonical Correspondance Analysis (CCA) ordination plot of biomarker responses for individuals collected in March at four sampling sites (represented by different colors), and the trace metals explaining the variation in the individual x biomarker matrix (blue arrows).
Biomarker values were scaled to ⅓ as to fit on the plot. The first two axes explain 44% of the variance in the data (40% and 4%, respectively). CS: Citrate synthase activity, MDA: MDA contents, SOD: SOD activity, GST: GST activity, LAC: Laccase activity.
Fig 6.
Median-joining network representing the 12 unique haplotypes found across 477 bp of the mitochondrial cox1 gene in 116 Mimachlamys varia individuals from four sampling sites.
Each filled circle represents a unique haplotype and its size is proportional to the number of individuals sharing this haplotype. Each circle is colored proportionally to the number of individuals from each sampling site. The number of mutations separating connected haplotypes is represented by tick marks on the line.
Table 4.
Genetic diversity indices for Mimachlamys varia (four sampling sites) calculated using sequences spanning 477 bp of the mitochondrial cox1 gene.
N: number of sequences analyzed; H: number of haplotypes; Hd: haplotype diversity; π: nucleotide diversity.