Abstract
Since 1990 the United Kingdom's Government-funded UK Cetacean Strandings Investigation Programme (CSIP) has recorded marine mammal strandings from around the UK coast and retrieved a proportion of (mainly cetacean) carcasses for necropsy using standardised protocols.1 A number of causes of deaths have been identified including entanglement in fishing gear (by-catch), boat/ship strikes, bottlenose dolphin (Tursiops truncatus) inter-species aggression and infanticide, starvation and a range of infectious (viral, bacterial, mycotic) and non-infectious diseases.1 Utilizing one of the largest toxicological datasets ever assembled for a marine mammal species, long-term research (1990–2011) on trends in potentially immune-suppressive pollutants in UK-stranded harbour porpoises (Phocoena phocoena) (n = 410–560), a sentinel species, has shown continual declines in tissue concentrations of butyltins4 all organochlorine pesticides and brominated flame retardants.4,5 In contrast, levels of polychlorinated biphenyls (PCBs) have remained at the highest blubber tissue concentrations and temporally stable since 1997.5 Elevated PCB levels have also been associated with infectious disease mortality2,3 and lymphoid depletion7 in case-control epidemiological studies of UK-stranded harbour porpoises utilising large sample sizes, but only in individuals where PCB levels exceed proposed thresholds for mammalian toxicity.6 PCBs concentrations in stranded/biopsied bottlenose dolphins (n = 50) and killer whales (Orcinus orca) (n = 23) across Europe are among the highest ever recorded on earth and are likely drivers of population declines/local extinctions. Killer whales now appear extinct in the Mediterranean Sea and only 47 known but non-reproductive individuals remain between northern parts of the UK and the continent of Africa. The great white shark (Carcharodon carcharias) occupies a similar trophic level and global distribution to the killer whale but is now only rarely encountered within the northern hemisphere globally and may be suffering the same cryptic PCB impact. Despite being banned more than 30 years ago, further efforts to reduce the PCB contamination of top marine predators in NE Atlantic and other oceanic regions are still urgently needed.
Acknowledgements
The research was conducted by UK Cetacean Strandings Investigation Program (CSIP) and the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) under contract to the UK Department for Environment, Food and Rural Affairs (Defra). All toxicological analyses were conducted by CEFAS Lowestoft and Burnham-on-Crouch laboratories in the UK.
* Presenting author
Literature Cited
1. Deaville R, Jepson PD. (compilers) 2011. CSIP Final Report for the period 1st January 2005–31st December 2010. UK Cetacean Strandings Investigation Programme: Report to the UK Department for Food and Rural Affairs and the Devolved Administrations. http://randd.defra.gov.uk/Document.aspx?Document=FinalCSIPReport2005-2010_finalversion061211released[1].pdf
2. Hall AJ, Hugunin K, Deaville R, Law RJ, Allchin CR, Jepson PD. 2006. The risk of infection from polychlorinated biphenyl exposure in harbour porpoise (Phocoena phocoena) - A case-control approach. Environmental Health Perspectives. 114, 704–711.
3. Jepson PD, Bennett PM, Deaville R, Allchin CR, Baker JR, Law RJ. 2005. Relationships between PCBs and health status in UK-stranded harbour porpoises (Phocoena phocoena). Environmental Toxicology and Chemistry. 24, 238–248.
4. Law RJ, Bolam T, James D, Barry J, Deaville R, Reid RJ, Penrose R, Jepson PD. 2012a. Butyltin compounds in liver of harbour porpoises (Phocoena phocoena) from the UK prior to and following the ban on the use of tributyltin in antifouling paints (1992–2005 & 2009). Marine Pollution Bulletin. 64: 2576–2580.
5. Law RJ, Barry J, Barber JL, Bersuder P, Deaville R, Reid RJ, Brownlow A, Penrose R, Barnett J, Loveridge J, Smith B, Jepson PD. 2012b. Contaminants in cetaceans from UK waters: status as assessed within the Cetacean Strandings Investigation Programme from 1990 to 2008. Marine Pollution Bulletin. 64: 1485–1494.
6. Kannan K, Blakenship AL, Jones PD, Giesy JP 2000. Toxicity reference values for the toxic effects of polychlorinated biphenyls to aquatic mammals. Human and Ecological Risk Assessment. 6, 181–201.
7. Yap X, Deaville R, Perkins MW, Penrose R, Law RJ, Jepson PD. (2012) Investigating links between polychlorinated biphenyl (PCB) exposure and thymic involution and thymic cysts in harbour porpoises (Phocoena phocoena). Marine Pollution Bulletin. 64: 2168–2176.