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Marine mammals are vulnerable to the bioaccumulation, biomagnification and lactational transfer of specific types of pollutants, such as industrial polychlorinated biphenyls (PCBs), due to their long-life spans, feeding at a high trophic level and unique fat stores that can serve as depots for these lipophilic contaminants. Currently, European countries are developing indicators for monitoring pollutants in the marine environment and assessing the state of biodiversity, requirements under both Regional Seas Conventions and European legislation. As sentinel species for marine ecosystem and human health, marine mammals can be employed to assess bioaccumulated contaminants otherwise below current analytical detection limits in water and lower trophic level marine biota. To aid the development of Regional Seas marine mammal contaminants indicators, as well as Member States obligations under descriptor 8 of the EU Marine Strategy Framework Directive, the current study aims to further develop appropriate methodological standards using data collected by the established UK marine mammal pollutant monitoring programme (1990 to 2017) to assess the trends and status of PCBs in harbour porpoises. Within this case study, temporal trends of PCB blubber concentration in juvenile harbour porpoises were analysed using multiple linear regression models and toxicity thresholds for the onset of physiological (reproductive and immunological) endpoints were applied to all sex-maturity groups. Mean PCB blubber concentrations were observed to decline in all harbour porpoise Assessment Units and OSPAR Assessment Areas in UK waters. However, a high proportion of animals were exposed to concentrations deemed to be a toxicological threat, though the relative proportion declined in most Assessment Units/Areas over the last 10 years of the assessment. Recommendations were made for improving the quality of the assessment going forward, including detailing monitoring requirements for the successful implementation of such an indicator., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Cetacean morbillivirus (CeMV) is an important global cause of morbidity and mortality in cetacean populations, with four pathological presentations including non-suppurative encephalitis. We describe an unusual case of dolphin morbillivirus (DMV)-associated non-suppurative encephalitis in a long-finned pilot whale (Globicephala melas), in which the lesions were orientated on the periventricular white matter and comprised prominent multifocal syncytia formation in the absence of systemic lesions. DMV RNA was detected in brain tissue by qRT-PCR and immunohistochemistry for morbillivirus antigen yielded intense labelling of syncytia in periventricular sites, with sparse involvement of the deeper neuroparenchyma. The pattern of lesions raises the possibility of viral dissemination through the cerebrospinal fluid, as described for canine distemper virus, suggesting that similar pathogenic mechanisms may be implicated in lesion development. Further investigation is required to establish the pathogenesis of CeMV encephalitis and the behaviour of the virus within the central nervous system of cetaceans., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Polychlorinated biphenyls (PCBs) are a group of 209 persistent and bio-accumulative toxic pollutants present as complex mixtures in human and animal tissues. Harbor porpoises accumulate some of the highest levels of PCBs because they are long-lived mammals that feed at a high trophic level. Studies typically use the sum of a suite of individual chlorobiphenyl congeners (CBs) to investigate PCBs in wildlife. However, toxic effects and thresholds of CB congeners differ, therefore population health risks of exposure may be under or over-estimated dependent on the congener profiles present. In this study, we found congener profiles varied with age, sex and location, particularly between adult females and juveniles. We found that adult females had the highest proportions of octa-chlorinated congeners whilst juveniles had the highest proportions of tri- and tetra-chlorinated congeners. This is likely to be a consequence of pollutant offloading between mothers and calves during lactation. Analysis of the individual congener toxicities found that juveniles were exposed to a more neurotoxic CB mixture at a time when they were most vulnerable to its effects. These findings are an important contribution towards our understanding of variation in congener profiles and the potential effects and threats of PCB exposure in cetaceans., (Copyright © 2019 The Author(s). Published by Elsevier B.V. All rights reserved.)

Marine top predators, including marine mammals, are known to bio-accumulate persistent pollutants such as polychlorinated biphenyls (PCBs), a serious conservation concern for these species. Although PCBs declined in European seas since the 1970s-1980s ban, considerable levels still persist in European and Mediterranean waters. In cetaceans, stranded animals are a valuable source of samples for pollutant studies, but may introduce both known and unknown biases. Biopsy samples from live, free-ranging cetaceans offer a better alternative for evaluating toxicological burdens of populations, especially when linked to known histories of identified individuals. We evaluated PCB and other organochlorine contaminants in free-ranging common bottlenose dolphins (Tursiops truncatus) from the Gulf of Trieste (northern Adriatic Sea), one of the most human-impacted areas in the Mediterranean Sea. Biopsies were collected from 32 male and female dolphins during 2011-2017. All animals were photo-identified and are part of a well-known population of about 150 individuals monitored since 2002. We tested for the effects of sex, parity and social group membership on contaminant concentrations. Males had significantly higher organochlorine concentrations than females, suggesting offloading from reproducing females to their offspring via gestation and/or lactation. Furthermore, nulliparous females had substantially higher concentrations than parous ones, providing further support for maternal offloading of contaminants. Overall, 87.5% of dolphins had PCB concentrations above the toxicity threshold for physiological effects in experimental marine mammal studies (9 mg/kg lw), while 65.6% had concentrations above the highest threshold published for marine mammals based on reproductive impairment in ringed seals (41 mg/kg lw). The potential population-level effects of such high contaminant levels are of concern particularly in combination with other known or suspected threats to this population. We demonstrate the utility of combining contaminant data with demographic parameters such as sex, reproductive output, etc., resulting from long-term studies., (Copyright © 2018. Published by Elsevier B.V.)

A suite of twenty organophosphorus flame retardant compounds have been determined in blubber and liver tissue of twenty harbour porpoises stranded or bycaught in the UK during 2012 in order to establish current levels of contamination. Fourteen of the twenty compounds were below the limits of quantification in all samples. Six could be quantified at maximum concentrations (in blubber) between 6.7 and 246μgkg(-1) wet weight. These levels do not suggest a high level of concern regarding potential impacts and do not indicate that routine monitoring in UK porpoises is warranted at this time., (Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.)

We report concentrations of organochlorine pesticides (HCB, HCHs, DDTs, dieldrin) and PCBs in the blubber of 43 common dolphins bycaught in fisheries operating off the SW coast of the UK from 1992 to 2006. Concentrations of ΣDDT (summed p,p'-DDT and its metabolites, p,p'-DDE and p,p'-TDE) and of 25 summed CB congeners ranged from 0.2 to 16.1 and 2.1 to 62.4 mg kg(-1) lipid weight, respectively. Concentrations of sum HCH, HCB and dieldrin were lower, ranging from not detected to 0.14, 0.01 to 0.27 and 0.01 to 0.73 mg kg(-1) lipid weight, respectively. All contaminants studied showed a downward time trend but only that for HCHs was statistically significant. Overall, 72% of the dolphins analysed had blubber PCB concentrations above an established toxicity threshold value., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

Liver butyltin concentrations (monobutyl, dibutyl and tributyltin (TBT)) in harbour porpoises (n=410) have been determined during 1992-2005, and again in 2009 following a ban on the use of tributyltin-based antifouling paints on ships. The aim was to assess the effectiveness of the regulation, which was implemented during 2003-2008. Since the ban was put in place summed butyltin concentrations have declined. Also, the percentage of animals in which TBT was detected has fallen sharply, indicating the cessation of fresh inputs. In 1992, 1993 and 1995, TBT was detected in 100% of samples analysed. In 2003-2005, once the implementation of the ban had begun, this fell to 61-72%, and in 2009, following the completion of the ban, had reduced to 4.3% (i.e. in only 1 of 23 samples analysed). Thus we conclude that the ban has proved effective in reducing TBT inputs to the seas from vessels., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

The associations between polychlorinated biphenyls (PCBs) exposure and involution of lymphoid tissue and development of epithelial-lined cysts in the thymus of UK-stranded harbour porpoises (Phocoena phocoena) (n=170) were tested. Percentage of thymic lymphoid tissue (%TLT) was histologically quantified. Multiple regression analyses (n=169) demonstrated significant positive correlation between %TLT and nutritional status (p<0.001) and significant negative association between %TLT and onset of sexual maturity (p<0.001). However, in a subgroup of porpoises with total PCB levels above a proposed threshold of toxicity (>17mg/kg lipid weight) (n=109), the negative association between %TLT (as dependent variable) and summed blubber concentrations of 25 chlorobiphenyl congeners (∑25CBs) remained significant (p<0.01) along with nutritional status (p<0.001) and onset of sexual maturity (p<0.001). These results suggest PCB-induced immuno suppression may be occurring in harbour porpoises in UK waters but only at concentrations that exceed proposed toxicity thresholds for marine mammals. In contrast, development of thymic cysts appears predominantly age-related., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Since 1990, tissue samples from UK-stranded and -bycaught cetaceans have been available for study of contaminant burdens. These have been used to study spatial and temporal trends in concentrations in UK waters, and to investigate potential associations between contaminants and health status. We describe the current status of cetaceans (primarily harbour porpoises, Phocoena phocoena) in UK waters in relation to pollution. Concentrations of BDEs, HBCD, and the organochlorine pesticides are declining. In contrast, concentrations of CBs have plateaued following earlier reductions due to regulation of use, and further reductions are likely to take decades. Blubber PCB concentrations are still at toxicologically significant levels in many harbour porpoises and regularly occur at even higher levels in bottlenose dolphins and killer whales due to their higher trophic level in marine food chains. Further reductions in PCB inputs into the marine environment are needed to mitigate risk from PCB exposure in these species., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

Harbour porpoises sampled within the UK Cetacean Strandings Investigation Programme have been analysed for 25 chlorobiphenyl congeners. In all, 440 porpoises stranded or bycaught during the period 1991-2005 were studied. There are regional differences in the trend in summed congener concentrations over time but, despite controls on PCBs having been in place for decades, they are declining only slowly. Their toxic impacts in UK porpoises - increased susceptibility to infectious disease mortality in the most contaminated individuals - looks likely to continue for some time yet. Further efforts to limit or eliminate PCB discharges to the marine environment are still needed., (Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.)