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

Abstract

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.

Contaminants in harbour porpoises beached along the Dutch coast : A first overview of contaminants in all age classes

“…This corresponds with earlier published levels of PCBs harbour porpoises in the UK (0.4 -160 mg/kg lw; Jepson et al, 2016) and North Sea (Table 5) (Weijs et al, 2009;Weijs et al, 2020;Mahfouz et al, 2014). Not enough samples were analysed per age group, sex and year to asses time Table 5 and Annex A).…”

“…PCB levels in 42 of the 91 samples of harbour porpoises beached along the Dutch coast were higher than the threshold level for toxicity of 9.0 mg/kg lw for onset of physiological endpoints in marine mammals (Jepson et al, 2016) (Figure 4). PCB levels in foetuses did not exceed this threshold level, suggesting no significant offloading in situ.…”

“…For females this was 80%, 43% and 0% respectively. (Jepson et al, 2016). See Annex H for number of samples per age group and sex.…”

“…chlorinated compounds (such as PolyChlorinatedBiphenyls -PCBs), brominated compounds (such as PolyBrominatedDiphenylEthersPBDEs), organotin compounds (such as TriButylTin -TBT) and perfluorinated compounds (PFCs)( Table 1). British studies relate PCB contamination in harbour porpoises to reproduction problems within their population, which points at possible risks for population growth and stability of the harbour porpoise population in the North Sea (Murphy et al 2015;Jepson et al 2016). These compounds are taken up by harbour porpoises via their food and are known to be bioaccumulative.…”

Best Practice Framework and Principles for Monitoring the Effect of Coastal Development on Marine Mammals

“…Such exposure can lead to many direct and indirect impacts including; temporary or permanent movement away from core habitats (Watson-Capps and Mann, 2005;Bejder et al, 2006b), disturbance to critical behaviors resulting in alterations to energy budgets and vital rates (Steckenreuter et al, 2011;Christiansen and Lusseau, 2015), increases in fishing interactions (Read, 2008;Mannocci et al, 2012;Allen et al, 2014), depletion in prey availability and increased competition for resources (Harwood, 2001), entanglement and ingestion of foreign debris (Harcourt et al, 1994;Page et al, 2004), disruption to acoustic communication systems with possible physiological damage to hearing abilities [Temporary Threshold Shift (TTS) and Permanent Threshold Shift (PTS)] (Richardson et al, 1995;Foote et al, 2004;Tyack, 2008;de Souza Albuquerque and da Silva Souto, 2013), increases in injury and mortality from vessel strikes (Wells and Scott, 1997;Laist et al, 2001;Panigada et al, 2006), bioaccumulation of toxins leading to immunosuppressant symptoms (Jepson et al, 2005;Litz et al, 2007;Cagnazzi et al, 2013a), reproductive collapse (Jepson et al, 2016), cerebral impairment (Cook et al, 2015), incidence of disease (Van Bressem et al, 1999) and the introduction of new parasites and pathogens (Delport et al, 2014(Delport et al, , 2015. The effect of these impacts upon populations of marine mammals, particularly where cumulative pressures are present, can lead to population-level consequences resulting in long-term shifts in habitat suitability, lower reproductive success, decreased health, increased mortality and population declines (Zhang et al, 2003;Lusseau, 2004;Wang et al, 2006;Bejder et al, 2006b;…”