Microplastics (MPs) are carriers of persistent organic pollutants (POPs). The influence of MPs on the toxicokinetics of POPs was investigated in a feeding experiment on Atlantic salmon (Salmo salar), in which fish were fed similar contaminant concentrations in feed with contaminants sorbed to MPs (Cont. MPs); feed with virgin MPs and contaminated feed (1:1), and feed with contaminants without MPs (Cont.). The results showed that the salmon fillets accumulated more POPs when fed with a diet where contaminants were sorbed to the MPs, despite the 125–250 μm size MPs themselves passing the intestines without absorption. Furthermore, depuration was significantly slower for several contaminants in fish fed the diet with POPs sorbed to the MPs. Modelled elimination coefficients and assimilation efficiencies of lipophilic chlorinated and brominated contaminants correlated with contaminant hydrophobicity (log Kow) within the diets and halogen classes. The more lipophilic the contaminant was, the higher was the transfer from feed to salmon fillet. The assimilation efficiency for the diet without MPs was 50–71% compared to 54–89% for the contaminated MPs diet. In addition, MPs caused a greater proportional uptake of higher molecular weight brominated congeners. In the present study, higher assimilation efficiencies and a significantly higher slope of assimilation efficiencies vs log Kow were found for the Cont. MPs diet (p = 0.029), indicating a proportionally higher uptake of higher-brominated congeners compared to the Cont. diet. Multiple variance analyses of elimination coefficients and assimilation efficiencies showed highly significant differences between the three diets for the chlorinated (p = 2E-06; 6E-04) and brominated (p = 5E-04; 4E-03) congeners and within their congeners. The perfluorinated POPs showed low assimilation efficiencies of 12%, which can be explained by faster eliminations corresponding to half-lives of 11–39 days, as well as a lower proportional distribution to the fillet, compared to e.g. the liver.

Many rivers have been impacted by heavy metal pollution in the past but the long-term legacies on biodiversity are difficult to estimate. The River Ulla (NW Spain) was impacted by tailings from a copper mine during the 1970–1980s but absence of baseline values and lack of subsequent monitoring have prevented a full impact assessment. We used archived fish scales of Atlantic salmon to reconstruct levels of historical copper pollution and its effects on salmon fitness. Copper bioaccumulation significantly increased over baseline values during the operation of the mine, reaching sublethal levels for salmon survival. Juvenile growth and relative population abundance decreased during mining, but no such effects were observed in a neighbouring river unaffected by mining. Our results indicate that historical copper exposure has probably compromised the fitness of this Atlantic salmon population to the present day, and that fish scales are suitable biomarkers of past river pollution.

This study reports the first baselines of plastic ingestion for three fish species that are common commercial and sustenance food fish in Newfoundland. Species collections occurred between 2015 and 2016 for Atlantic cod (Gadus morhua), Atlantic salmon (Salmo salar), and capelin (Mallotus villosus). The frequency of occurrence (%FO) of plastic ingestion for both Atlantic salmon (n = 69) and capelin (n = 350) was 0%. Of the 1010 Atlantic cod individuals collected over two years, 17 individuals had ingested plastics, a %FO of 1.68%. This is the only multi-year investigation of plastic ingestion in Atlantic cod for the Northwest Atlantic, and the first baseline of plastic ingestion in Atlantic salmon and capelin on the island of Newfoundland. Considering the ecological, economic, and cultural importance of these fish species, this study is the beginning of a longitudinal study of plastic ingestion to detect any future changes in contamination levels.