Legacy persistent organic pollutants among multiple cetacean species in the Northwest Atlantic

• Published in: The Science of the total environment Vol. 954; p. 176746
• Main Authors: Remili, Anaïs, McKinney, Melissa A., Maldonado-Rodriguez, Ambar, Ferguson, Steven H., Caputo, Michelle, Kiszka, Jeremy J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-12-2024
• Subjects: Blubber; Canada; DDTs; Dietary tracers; Marine mammals; PCBs; Whales; DDTs; PCBs; Dietary tracers; Canada; Whales; Blubber; Marine mammals
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.176746

The historical contamination of eastern Canadian shelf waters remains an ongoing concern, predominantly stemming from anthropogenic discharges in the Great Lakes region. Although legacy persistent organic pollutants (POPs) were banned decades ago, it remains unclear whether their concentrations have sufficiently decreased to safer levels in cetaceans that feed in the continental shelf waters of the northwestern Atlantic. This study compares polychlorinated biphenyl (PCB) and organochlorine pesticide (OC) accumulation in six cetacean species sampled in the Northwest Atlantic from 2015 to 2022. We assessed the influence of relative trophic level and foraging habitat preferences on POP accumulations among species using stable isotopes and fatty acids as dietary tracers. We further identified the species most susceptible to the effects of these contaminants. Killer whales (Orcinus orca) exhibited the highest PCB (∼100 mg/kg lw) and OC concentrations, followed by other odontocetes, with lowest concentrations in mysticetes. Stable isotope analysis revealed an unexpected lack of correlation between δ15N values and contaminant levels. However, there was a positive correlation between δ13C values and POP concentrations. Cetaceans foraging on pelagic prey species, as indicated by elevated proportions of the FA markers 22:1n11 and 20:1n9, had lower contaminant loads compared to cetaceans with benthic/coastal FA signatures. PCB and DDT (dichlorodiphenyltrichloroethane) concentrations are lower now in most cetacean species than in the 1980s and 1990s, likely due to regulatory measures restricting their production and use. Although current PCB concentrations for most species are under the thresholds for high risks of immune and reproductive failure, concentrations in killer whales exceed all established toxicity thresholds, underscoring the need for further action to reduce sources of these contaminants to the continental shelf waters of the northwestern Atlantic.
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•Six cetacean species (3 odontocetes, 3 mysticetes) were sampled in NW Atlantic continental shelf waters from 2015-2022.•Legacy POP concentrations were lowest in baleen whales, followed by small odontocetes, and highest in killer whales (Orcinus orca).•POPs were correlated with dietary tracers, with higher levels found in species feeding at higher trophic levels and on coastal/benthic prey.•POP concentrations are lower than those reported in the 1980s and 1990s.•Current POP concentrations in killer whales remain above all toxicity thresholds for marine mammals, including risks of reproductive failure.