peer reviewed | Harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) were found to differ in the ability to metabolize polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Biomagnification factors (BMFs), calculated between both predators and their prey (sole – Solea solea and whiting – Merlangius merlangus), had a large range of variation (between 0.5 and 91 for PCBs and between 0.6 and 53 for PBDEs). For the higher chlorinated PCBs and the highest brominated PBDEs, the BMF values in adult males were significantly higher than in the juvenile individuals of both species. BMF values of hexa- to octa-PCBs were the highest, suggesting reduced ability to degrade these congeners. Harbour porpoises had higher BMFs for lower chlorinated PCBs and for all PBDEs compared to harbour seals. Other factors, which may influence biomagnification, such as the octanol–water partition coefficients and the trophic level position measured through stable isotope (d15N) analysis, were found to be of lesser importance to predict biomagnification in the studied food chain.

The objective of the present study was to investigate recent concentrations of perfluoroalkyl substances (PFASs) in white whales (Delphinapterus leucas) from Svalbard and compare them to concentrations found in white whales sampled from that same area 15 years ago. Plasma collected from live-captured white whales from two time periods (2013–2014, n = 9, and 1996–2001, n = 11) were analysed for 19 different PFASs. The 11 PFASs detected included seven C₈–C₁₄ perfluoroalkyl carboxylates (PFCAs) and three C₆–C₈ perfluoroalkyl sulfonates (PFSAs) as well as perfluorooctane sulfonamide (FOSA). Recent plasma concentrations (2013–2014) of the dominant PFAS in white whales, perfluorooctane sulfonate (PFOS; geometric mean = 22.8 ng/mL), was close to an order of magnitude lower than reported in polar bears (Ursus maritimus) from Svalbard. PFOS concentrations in white whales were about half the concentrations in harbour (Phoca vitulina) and ringed (Pusa hispida) seals, similar to hooded seals (Cystophora cristata) and higher than in walruses (Odobenus rosmarus) from that same area. From 1996 to 2001 to 2013–2014, plasma concentrations of PFOS decreased by 44%, whereas four C₉₋₁₂ PFCAs and total PFCAs increased by 35–141%. These results follow a similar trend to what has been reported in other studies of Arctic marine mammals from Svalbard. The most dramatic change has been the decline of PFOS concentrations since 2000, corresponding to the production phase-out of PFOS and related compounds in many countries around the year 2000 and a global restriction on these substances in 2009. Still, the continued dominance of PFOS in white whales, and increasing concentration trends for several PFCAs, even though exposure is relatively low, calls for continued monitoring of concentrations of both PFCAs and PFSAs and investigation of biological effects.

The ubiquity of pharmaceuticals in the aquatic environment and the accumulation in organisms of lower trophic levels have been documented. The immunotoxicity of these xenobiotics has however been little investigated. This study assessed the effects of pharmaceuticals on the immune responses of harbor seal lymphocytes. Peripheral blood mononuclear cells isolated from harbor seal pups were exposed to varying concentrations of 17α-ethinyl estradiol (250–50,000μg/L), naproxen (500–100,000μg/L), carbamazepine (500–100,000μg/L), erythromycin (750–150,000μg/L) and binary mixtures thereof in vitro. All individual compounds and mixtures inhibited lymphocyte proliferation. Mixture effects were non-additive and predictive values overestimated the inhibition of proliferation. Male pups were more sensitive to erythromycin exposure. Comparison with the sensitivity of the 11B7501 cell line showed a higher sensitivity of pups to individual compounds and the inverse trend for mixtures. Based on our results, we hypothesize that pharmaceuticals may have the potential to interrupt immune functions in harbor seals.

The potential risk of pharmaceuticals in the environment to top-predators is still largely unknown. In this study, we assessed the immunotoxic effects of ten pharmaceuticals individually and as mixtures on a harbor seal (Phoca vitulina) B lymphoma cell line. A significant reduction in lymphocyte transformation was observed following an exposure to 12,500μg/L 17α-ethinyl estradiol and 25,000μg/L naproxen. Exposure to 12,500μg/L 17α-ethinyl estradiol decreased the percentage of cell in the G0/G1 phase of the cell cycle while increasing the percentage of cells in the S phase. Carbamazepine exposure increased the amount of cells in the G2/M phase. Binary mixtures showed synergistic effects in lymphocyte transformation, cell cycle and apoptosis assays. Concentrations inducing toxic effects in the cell line were similar to those affecting fish in previous studies. A reduction of functional activities of the immune system may lead to altered host resistance to pathogens in free-ranging pinnipeds.

Anthropogenic micro debris in the marine environment is a growing concern worldwide, affecting multiple trophic levels, from primary consumers such as zooplankton, to meso- and apex predators like marine mammals and marine birds. In 2016–2017, during the processing of harbor seal (Phoca vitulina vitulina) and gray seal (Halichoerus grypus atlantica) fecal samples for fish otoliths and organic hard parts as part of a prey study, anthropogenic micro debris (>500 μm) was detected in 6% (n = 2/32) of harbor seal and 1% (n = 2/129) of gray seal samples. Spectral analysis identified the fragments as cellophane, alkyd resin and poly(ethylene:propylene:diene) (EPDM) rubber. These results show the potential indirect ingestion of micro debris, which can impact the health and welfare of marine wildlife. This is the first report of micro debris presence in wild populations of phocid seals for the northwestern Atlantic.

There is global interest in marine renewable energy from underwater tidal turbines. Due to overlap in animal habitat with locations for tidal turbines, the potential for collisions has led to concern around strike risk. Using data from tagged harbor seals collected before construction and after operation of the SeaGen tidal turbine in Northern Ireland, this study quantifies risks of an operational turbine to harbor seals by taking into account turbine characteristics, tidal state, and seal behavior. We found 68% spatial avoidance (95% C.I., 37%, 83%) by harbor seals within 200 m of the turbine. When additionally accounting for variation in seal occupancy over depth and tidal flows, there is an overall reduction in collision risk from 1.29 to 0.125 seals per tidal cycle (90.3% reduction; (95% C.I., 83%, 98%)) compared to risk calculated under assumptions of uniform habitat use. This demonstrates the need to incorporate environmental conditions to properly assess strike risk.

To evaluate the transfer of Sellafield-derived radiocarbon (14C) to top predators in the UK marine environment, 14C activities were examined in stranded marine mammals. All samples of harbour porpoise (Phocoena phocoena) obtained from the Irish Sea showed 14C enrichment above background. Mammal samples obtained from the West of Scotland, including harbour porpoise, grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) showed 14C enrichment but to a lesser extent. This study demonstrates, for the first time, enriched 14C is transferred through the marine food web to apex predators as a consequence of ongoing nuclear reprocessing activities at Sellafield. Total Sellafield 14C discharge activity 24months prior to stranding and, in particular, distance of animal stranding site from Sellafield are significant variables affecting individual 14C activity. 14C activities of West of Scotland harbour porpoises suggest they did not forage in the Irish Sea prior to stranding, indicating a high foraging fidelity.