Organohalogen contaminants of emerging concern in common dolphins (Delphinus delphis) from the Bay of Biscay (NE Atlantic): occurrence and 2000–2023 temporal patterns

International audience

English. <div><p>The contamination of marine mammals by legacy pollutants has been largely studied in oceans worldwide. However, international regulations have given rise to the replacement of legacy substances by alternative compounds, which represent a potential additional threat to marine mammal health and conservation. In this study, we investigated the occurrence and temporal trends of contaminants of emerging concern (CECs) in the blubber of common dolphins (Delphinus delphis) from the Bay of Biscay, North-East Atlantic, and in their major prey. Alternative brominated flame retardants were below the limits of quantification in all samples, while dechlorane-related compounds were identified as the major CECs, at levels of 4.6 ± 5.9 ng g -1 lw, i.e. similar to or higher than those reported in various marine mammals from other oceanic regions. The concentrations of 3,6dichlorocarbazole (3,6-CCZ), the major polyhalogenated carbazole, and of methyl-triclosan were one order of magnitude lower. The halogenated natural products, methoxylated polybrominated diphenyl ethers (MeO-BDEs), were also investigated and showed substantially higher concentrations than all CECs, i.e. 322 ± 214 ng g -1 lw. Declorane-602, anti-monohydro dechlorane plus and MeO-BDEs were the only compounds showing biomagnification between small pelagic fish and dolphins. No significant differences in most CEC concentrations were found over the studied time period, indicating that these compounds are still emitted in the environment and/or have long residence times in the dolphins' blubber. Conversely, methyl-triclosan concentrations significantly decreased over the studied period. An increase in MeO-BDE concentrations in the last two decades might reveal a change in algal production in relation to global warming.</p></div>