Contamination Profile and Health Status of Mya arenaria in the St-Lawrence-Saguenay Marine Park

Clams represent an important part of the marine benthic community and are food sources for invertebrates (worms, amphipods), fish, and mammals. The purpose of this study was to examine the contamination and health status of feral Mya arenaria clam populations from the Saint-Lawrence river and Saguenay fjord at sites of anthropogenic pollution (harbors), a high residency beluga whale area and a reference site under no direct contact of pollution. Intertidal clams were collected for nanoplastics (NPs), dibutyl phthalate (DBP), metal contamination and health status assessments. Health status consisted of the evaluation of oxidative stress, protein aggregation, esterase, and carbonic anhydrase at the biochemical level, followed by morphological assessments (shell mass, condition factor, growth index) and resistance to air emersion. The data revealed that clams collected from polluted sites had elevated levels of NPs, DBP, Cd, Ce, Fe, Cu, Sn and Zn compared to the reference site. Surprisingly, the beluga high residency area site was also contaminated by these contaminants (with the exception of Cd), especially for Sn, NPs and DBP. These clams contained elevated levels of peroxidase activity, protein aggregation, esterase, (mantle) carbonic anhydrase and accumulated lipids. The clams displayed at least at one polluted or whale residency site, decreased condition factor, shell mass ratio, air survival time and increased growth index. Cluster analysis revealed that the above contaminants were strongly associated with carbonic anhydrase, esterase, peroxidase and protein aggregation changes but less so with morphological changes. In conclusion, feral clam populations are contaminated by plastic compounds, including the plasticizer DBP and Sn, contributing to reduced shell mass.