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      PCB pollution continues to impact populations of orcas and other dolphins in European waters


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          Organochlorine (OC) pesticides and the more persistent polychlorinated biphenyls (PCBs) have well-established dose-dependent toxicities to birds, fish and mammals in experimental studies, but the actual impact of OC pollutants on European marine top predators remains unknown. Here we show that several cetacean species have very high mean blubber PCB concentrations likely to cause population declines and suppress population recovery. In a large pan-European meta-analysis of stranded (n = 929) or biopsied (n = 152) cetaceans, three out of four species:- striped dolphins (SDs), bottlenose dolphins (BNDs) and killer whales (KWs) had mean PCB levels that markedly exceeded all known marine mammal PCB toxicity thresholds. Some locations (e.g. western Mediterranean Sea, south-west Iberian Peninsula) are global PCB “hotspots” for marine mammals. Blubber PCB concentrations initially declined following a mid-1980s EU ban, but have since stabilised in UK harbour porpoises and SDs in the western Mediterranean Sea. Some small or declining populations of BNDs and KWs in the NE Atlantic were associated with low recruitment, consistent with PCB-induced reproductive toxicity. Despite regulations and mitigation measures to reduce PCB pollution, their biomagnification in marine food webs continues to cause severe impacts among cetacean top predators in European seas.

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          Most cited references43

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          Gas-bubble lesions in stranded cetaceans.

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            Cetacean abundance and distribution in European Atlantic shelf waters to inform conservation and management

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              "Gas and fat embolic syndrome" involving a mass stranding of beaked whales (family Ziphiidae) exposed to anthropogenic sonar signals.

              A study of the lesions of beaked whales (BWs) in a recent mass stranding in the Canary Islands following naval exercises provides a possible explanation of the relationship between anthropogenic, acoustic (sonar) activities and the stranding and death of marine mammals. Fourteen BWs were stranded in the Canary Islands close to the site of an international naval exercise (Neo-Tapon 2002) held on 24 September 2002. Strandings began about 4 hours after the onset of midfrequency sonar activity. Eight Cuvier's BWs (Ziphius cavirostris), one Blainville's BW (Mesoplodon densirostris), and one Gervais' BW (Mesoplodon europaeus) were examined postmortem and studied histopathologically. No inflammatory or neoplastic processes were noted, and no pathogens were identified. Macroscopically, whales had severe, diffuse congestion and hemorrhage, especially around the acoustic jaw fat, ears, brain, and kidneys. Gas bubble-associated lesions and fat embolism were observed in the vessels and parenchyma of vital organs. In vivo bubble formation associated with sonar exposure that may have been exacerbated by modified diving behavior caused nitrogen supersaturation above a threshold value normally tolerated by the tissues (as occurs in decompression sickness). Alternatively, the effect that sonar has on tissues that have been supersaturated with nitrogen gas could be such that it lowers the threshold for the expansion of in vivo bubble precursors (gas nuclei). Exclusively or in combination, these mechanisms may enhance and maintain bubble growth or initiate embolism. Severely injured whales died or became stranded and died due to cardiovascular collapse during beaching. The present study demonstrates a new pathologic entity in cetaceans. The syndrome is apparently induced by exposure to mid-frequency sonar signals and particularly affects deep, long-duration, repetitive-diving species like BWs.

                Author and article information

                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                14 January 2016
                : 6
                [1 ]Institute of Zoology, Zoological Society of London , Regent’s Park, London NW1 4RY, UK
                [2 ]Centre for Environment, Fisheries and Aquaculture Science , Pakefield Road, Lowestoft, NR33 0HT, UK
                [3 ]Department of Animal Biology and Biodiversity Research Institute (IRBio), University of Barcelona , Barcelona, Spain
                [4 ]Scottish Marine Animal Stranding Scheme, SRUC Veterinary Services Drummondhill , Stratherrick Road, Inverness, IV2 4JZ, UK
                [5 ]Environment and Sustainability Institute, University of Exeter , Cornwall Campus, Penryn, Cornwall TR10 9EZ, UK
                [6 ]Marine and Freshwater Research Centre, Galway-Mayo Institute of Technology , Galway, Ireland
                [7 ]CIRCE, Conservation, Information and Research on Cetaceans , Cabeza de Manzaneda 3, Algeciras, 11390, Spain
                [8 ]Marine Animal Tissue Bank – Portugal, Soc. Portuguesa de Vida Selvagem, Dep. Biologia - Univ. do Minho & CESAM , Portugal
                [9 ]Evolutionary Biology Centre, Uppsala University , Norbyvägen 18D, SE‐752 36 Sweden
                [10 ]Morigenos-Slovenian Marine Mammal Society , Kidričevo nabrežje 4, 6330 Piran, Slovenia
                [11 ]Institute for Biodiversity Studies, Science and Research Centre, University of Primorska , Koper, Slovenia
                [12 ]Department of Biodiversity, Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska , Koper, Slovenia
                [13 ]Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC) , Americo Vespuccio S/N, Isla Cartuja, 42092, Sevilla, Spain
                [14 ]Cornwall Wildlife Trust Marine Strandings Network, Five Acres , Allet, Truro, TR4 9DJ, UK
                [15 ]Coordinadora para o Estudio dos Mamíferos Mariños (CEMMA) , Apartado 15, 36380 Gondomar, Pontevedra, Spain
                [16 ]Sociedad de Estudios de Cetáceos en Canarias (SECAC) , Lanzarote, Spain
                [17 ]Marine Environmental Monitoring, Penwalk, Llechryd , Cardigan, Ceredigion, SA43 2PS, UK
                [18 ]The Natural History Museum , Cromwell Road, London SW7 5BD, UK
                [19 ]Facultad de Veterinaria, Universidad de Las Palmas de Gran Canaria , Gran Canaria, Spain
                Author notes
                Copyright © 2016, Macmillan Publishers Limited

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