Dataset Information

Preying on seals pushes killer whales from Norway above pollution effects thresholds.

ABSTRACT: Killer whales (Orcinus orca) are at risk from high levels of biomagnifying pollutants, such as polychlorinated biphenyls (PCBs) and mercury (Hg). Previous toxicological risk assessments for the Norwegian killer whale population have assumed fish as the primary prey source, and assessed the population as below established effect thresholds. However, some individuals have recently been identified to also feed on seals. This study is the first to quantify levels of pollutants in seal-eating killer whales from northern Norway, and to measure Hg levels in the skin of killer whales worldwide. We found higher levels of all pollutants in seal-eating than fish-eating killer whales, including the emerging brominated flame retardants pentabromoethylbenzene (PBEB), pentabromotoluene (PBT) and hexabromobenzene (HBB). Sum polychlorinated biphenyls (?PCBs) in the blubber of seal-eaters (n?=?7, geometric mean?=?46 µg/g l.w.) were four times higher than fish-eaters (n?=?24, geometric mean?=?11 µg/g l.w.), which pushed all seal-eating individuals above multiple thresholds for health effects. Total Hg levels in skin of seal-eaters (n?=?10, arithmetic mean?=?3.7 µg/g d.w.) were twice as high as in fish-eaters (n?=?28, arithmetic mean?=?1.8 µg/g d.w.). Our results indicate that by feeding on higher trophic prey, the Norwegian killer whale population is at higher risk of health effects from pollution than previously assumed.

SUBMITTER: Andvik C

PROVIDER: S-EPMC7368030 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Preying on seals pushes killer whales from Norway above pollution effects thresholds.

Andvik Clare C Jourdain Eve E Ruus Anders A Lyche Jan L JL Karoliussen Richard R Borgå Katrine K

Scientific reports 20200717 1

Killer whales (Orcinus orca) are at risk from high levels of biomagnifying pollutants, such as polychlorinated biphenyls (PCBs) and mercury (Hg). Previous toxicological risk assessments for the Norwegian killer whale population have assumed fish as the primary prey source, and assessed the population as below established effect thresholds. However, some individuals have recently been identified to also feed on seals. This study is the first to quantify levels of pollutants in seal-eating killer ...[more]

PMID: 32681067

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Project description:In cetaceans, blubber is the primary and largest lipid body reservoir. Our current understanding about lipid stores and uses in cetaceans is still limited, and most studies only focused on a single narrow snapshot of the lipidome. We documented an extended lipidomic fingerprint in two cetacean species present in northern Norway during wintertime. We were able to detect 817 molecular lipid species in blubber of killer whales (Orcinus orca) and humpback whales (Megaptera novaeangliae). The profiles were largely dominated by triradylglycerols in both species and, to a lesser extent, by other constituents including glycerophosphocholines, phosphosphingolipids, glycerophosphoethanolamines, and diradylglycerols. Through a unique combination of traditional statistical approaches, together with a novel bioinformatic tool (LION/web), we showed contrasting fingerprint composition between species. The higher content of triradylglycerols in humpback whales is necessary to fuel their upcoming half a year fasting and energy-demanding migration between feeding and breeding grounds. In adipocytes, we assume that the intense feeding rate of humpback whales prior to migration translates into an important accumulation of triacylglycerol content in lipid droplets. Upstream, the endoplasmic reticulum is operating at full capacity to supply acute lipid storage, consistent with the reported enrichment of glycerophosphocholines in humpback whales, major components of the endoplasmic reticulum. There was also an enrichment of membrane components, which translates into higher sphingolipid content in the lipidome of killer whales, potentially as a structural adaptation for their higher hydrodynamic performance. Finally, the presence of both lipid-enriched and lipid-depleted individuals within the killer whale population in Norway suggests dietary specialization, consistent with significant differences in δ15N and δ13C isotopic ratios in skin between the two groups, with higher values and a wider niche for the lipid-enriched individuals. Results suggest the lipid-depleted killer whales were herring specialists, while the lipid-enriched individuals might feed on both herrings and seals.

Dataset Information

Preying on seals pushes killer whales from Norway above pollution effects thresholds.

Publications

Preying on seals pushes killer whales from Norway above pollution effects thresholds.

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