Investigating decadal changes in persistent organic pollutants in Scottish grey seal pups

Abstract

1. Persistent organic pollutants (POPs) remain a risk to marine ecosystem health.POPs accumulate in fat tissue and are biomagnified up through food webs, generating high concentrations in apex predators, including marine mammals. Seals are thus often cited as sentinels of marine environment POP levels. Measuring changes across decadal timescales in these animals is key to understanding the effectiveness of regulations controlling POPs, predicting health, population, and ecosystem level impacts, and informing conservation and management strategies.Information on recent changes in legacy POPs in seals is relatively sparse, however, and datasets are not always continuous in the absence of dedicated POP monitoring programmes. 2. Here, POP concentrations in the blubber of weaned grey seal pups from the Isle of May, Scotland, were compared between studies investigating POP impacts on survival and energy balance in 2002, and in 2015-17. By 2017, the total dioxin-like polychlorinated biphenyls (ΣDL-CBs) and the total non-dioxin-like polychlorinated biphenyls (ΣNDL-CBs) had decreased to~75% of 2002 levels. 3. The organochlorine pesticides (OCPs), dichlorodiphenyltrichoroethane (ΣDDT), dichlorodiphenyldichloroethylene (DDE), and dichlorodiphenyldichoroethane (DDD), and some CB congeners, did not fall over the 15-year period; however, the power to detect small changes at low concentrations was limited. 4. High DDE and a lack of change in DDD are likely to reflect the low excretion of DDT metabolites, rather than recent exposure.5. The limited change in many POPs over 15 years suggest that risks remain for energy balance, endocrine status, and immune function in grey seal pups, with contingent effects on conservation and management objectives for this species.6. These data highlight the need for long-term datasets and parity in sampling and analytical methods to evaluate continuing impacts of POPs in grey seals and on marine ecosystems more widely.

Interactions between Environmental Contaminants and Gastrointestinal Parasites: Novel Insights from an Integrative Approach in a Marine Predator

“…Here, we focus on a population of European shags Phalacrocorax aristotelis (hereafter shags) breeding in the Firth of Forth, a Scottish estuary with over 200 years of contaminant inputs that originate from agrochemical and petrochemical activities and domestic discharges from large urban agglomerations . Studies on marine predators in the region have shown high and slowly declining concentrations of Hg and organochlorine pollutants, − while exposure to other TEs and PFAS is unknown. The shag is a long-lived, predominantly piscivorous, and pursuit-diving seabird that feeds primarily on the seabed in inshore waters − and is thus exposed to sediment-derived contamination .…”

Concentrations of some legacy pollutants have increased in South Australian bottlenose dolphins from 1989 to 2014

“…Consequently, concentrations of PCBs in Australian wildlife were usually relatively low, which probably explains the scarcity of PCB data in Australian marine apex predators. Despite this, it is concerning that PCB levels have almost doubled in South Australian marine top predators while they have been decreasing or stabilising in other parts of the world (Ross et al, 2013;Jepson et al, 2016;Robinson et al, 2019). For both compound classes, explanations are probably a combination of local inputs such as effluent discharge, poor (electronic) waste management, industrial and agricultural runoff, and global sources such as oceanic currents and atmospheric deposition fluxes.…”

Polychlorinated Biphenyls (PCBs) and Sex Hormone Concentrations in Ringed and Grey Seals: A Possible Link to Endocrine Disruption?

“…The current population growth rate is now 5% a year according to the latest Baltic Seal census (Luke 2016). Although the concentrations of PCBs have declined in seals, they remain the predominating contribution to organic chemicals levels in pinnipeds (Bjurlid et al 2018;Ross et al 2009;Robinson et al 2019). PBDEs, with similar modes of action to PCBs, still enter marine food chains as bans of these endocrine-disrupting chemicals were more recent.…”

“…Since the enforcement of international bans on POPs (UNEP 2017), concentrations have declined in Northern European, Canadian Atlantic, and Arctic marine ecosystems, and this is mirrored in tissue concentrations of local seal populations (Muir and deWit 2010;Ross et al 2013;Bjurlid et al 2018;Brown et al 2018;HELCOM 2018a, b). However, these "legacy chemicals," due to their persistent nature and global distribution, still persist and PCBs remain the greatest contribution to total organic pollutant burdens in seals and other apex predators (Greaves et al 2012;Shaw et al 2012;Brown et al 2018;AMAP 2018;Schnitzlera et al 2019;Robinson et al 2019). In this study, the effects of PCBs on circulating sex hormones (progesterone [P4]; 17α-hydroxy progesterone [17α-OH-P4]; testosterone [T4]; 17β-estradiol [E2]; estrone [E3]) were investigated as evidence for endocrine disruption in wild seal populations.…”