Abstract
Pollutant concentrations are poorly known for the largest animals on Earth, blue whales Balaenoptera musculus and fin whales Balaenoptera physalus. In this study, concentrations of persistent organic pollutants (POPs) were determined in blubber biopsies and stable isotope values for nitrogen (δ15N) and carbon (δ13C) were measured using skin biopsies for 18 blue whales and 12 fin whales sampled in waters surrounding the Svalbard Archipelago, Norway. The samples were collected in summer during the period 2014–2018. POPs were dominated by DDTs, PCBs and toxaphenes, with median concentrations in blue/fin whales being 208/341, 127/275 and 133/233 ng/g lipid weight, respectively. Linear models indicated that pollutant concentrations were 1.6–3 times higher in fin whales than in blue whales, which is likely related to the higher trophic positions of fin whales, as indicated by their higher δ15N. Lower δ13C in fin whales suggests that they feed at higher latitudes than blue whales; these values were not correlated with pollutant concentrations. Pollutant levels were approximately twice as high in males compared to females (intraspecifically), which indicates that females of these species offload pollutants to their offspring during gestation and lactation, similar to many other mammalian species. Pollutant concentrations in balaenopterid whales from Svalbard waters were generally much lower than in conspecific whales from the Mediterranean Sea or the Gulf of California, but higher than those in conspecifics from the Antarctic Peninsula.
Highlights
The Arctic is warming twice as fast as anywhere else on Earth, and recent reports have documented an increasing frequency of southern species in the Arctic (Kortsch et al, 2012; Laidre et al, 2015)
Based on linear model estimates, stable isotope values for δ15N were 0.92‰ units higher in fin whales than in blue whales, whereas δ13C values were 1.14‰ lower in fin whales than in blue whales (Table 2)
Stable isotope values were similar in males and females, when species-differences were taken into account (−0.11, 95% confidence intervals (CIs): −0.62, 0.41 and −0.03, 95% CI: −1.10, 1.05 for δ15N and δ13C, respectively) (Table 2)
Summary
The Arctic is warming twice as fast as anywhere else on Earth, and recent reports have documented an increasing frequency of southern species in the Arctic (Kortsch et al, 2012; Laidre et al, 2015). There has been an expansion of the distributional ranges of many invertebrate and fish species into the Arctic (Doney et al, 2012; Fossheim et al, 2015; Kortsch et al, 2012; Vihtakari et al, 2018), and the new communities of boreal species have attracted new predators such as balaenopterid whales. Along the shelf breaks west and north of Svalbard Archipelago, the sighting rate of blue whales (Balaenoptera musculus) and fin whales (Balaenoptera physalus) has increased in recent years (Storrie et al, 2018; Vacquié-Garcia et al, 2017). In addition to inducing distributional shifts, global warming is causing remobilization of a large number of POPs from repositories in the Arctic, due to rising temperatures (Ma et al, 2011)
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