Highly contaminated river otters (Lontra canadensis) are effective biomonitors of environmental pollutant exposure

River otters (Lontra canadensis) are apex predators that bioaccumulate contaminants via their diet, potentially serving as biomonitors of watershed health. They reside throughout the Green-Duwamish River, WA (USA), a watershed encompassing an extreme urbanization gradient, including a US Superfund site slated for a 17-year remediation. The objectives of this study were to document baseline contaminant levels in river otters, assess otters’ utility as top trophic-level biomonitors of contaminant exposure, and evaluate the potential for health impacts on this species. We measured a suite of contaminants of concern, lipid content, nitrogen stable isotopes (δ15N), and microsatellite DNA markers in 69 otter scat samples collected from twelve sites. Landcover characteristics were used to group sampling sites into industrial (Superfund site), suburban, and rural development zones. Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ether flame-retardants (PBDEs), dichlorodiphenyl-trichloroethane and its metabolites (DDTs), and polycyclic aromatic hydrocarbons (PAHs) increased significantly with increasing urbanization, and were best predicted by models that included development zone, suggesting that river otters are effective biomonitors, as defined in this study. Diet also played an important role, with lipid content, δ15N or both included in all best models. We recommend river otter scat be included in evaluating restoration efforts in this Superfund site, and as a potentially useful monitoring tool wherever otters are found. We also report ΣPCB and ΣPAH exposures among the highest published for wild river otters, with almost 70% of samples in the Superfund site exceeding established levels of concern.publishedVersio

Potent Phototoxicity of Marine Bunker Oil to Translucent Herring Embryos after Prolonged Weathering

Pacific herring embryos (Clupea pallasi) spawned three months following the Cosco Busan bunker oil spill in San Francisco Bay showed high rates of late embryonic mortality in the intertidal zone at oiled sites. Dead embryos developed to the hatching stage (e.g. fully pigmented eyes) before suffering extensive tissue deterioration. In contrast, embryos incubated subtidally at oiled sites showed evidence of sublethal oil exposure (petroleum-induced cardiac toxicity) with very low rates of mortality. These field findings suggested an enhancement of oil toxicity through an interaction between oil and another environmental stressor in the intertidal zone, such as higher levels of sunlight-derived ultraviolet (UV) radiation. We tested this hypothesis by exposing herring embryos to both trace levels of weathered Cosco Busan bunker oil and sunlight, with and without protection from UV radiation. Cosco Busan oil and UV co-exposure were both necessary and sufficient to induce an acutely lethal necrotic syndrome in hatching stage embryos that closely mimicked the condition of dead embryos sampled from oiled sites. Tissue levels of known phototoxic polycyclic aromatic compounds were too low to explain the observed degree of phototoxicity, indicating the presence of other unidentified or unmeasured phototoxic compounds derived from bunker oil. These findings provide a parsimonious explanation for the unexpectedly high losses of intertidal herring spawn following the Cosco Busan spill. The chemical composition and associated toxicity of bunker oils should be more thoroughly evaluated to better understand and anticipate the ecological impacts of vessel-derived spills associated with an expanding global transportation network

Geographic Variation of Persistent Organic Pollutant Levels in Humpback Whale (\u3ci\u3eMegaptera novaeangliae\u3c/i\u3e) Feeding Areas of the North Pacific and North Atlantic

Seasonal feeding behavior and high fidelity to feeding areas allow humpback whales (Megaptera novaeangliae) to be used as biological indicators of regional contamination. Biopsy blubber samples from male individuals (n=67) were collected through SPLASH, a multinational research project, in eight North Pacific feeding grounds. Additional male samples (n=20) were collected from one North Atlantic feeding ground. Persistent organic pollutants were measured in the samples and used to assess contaminant distribution in the study areas. North Atlantic (Gulf of Maine) whales were more contaminated than North Pacific whales, showing the highest levels of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and chlordanes. The highest dichlorodiphenyltrichloroethane (DDT) levels were detected in whales feeding off southern California, USA. High-latitude regions were characterized by elevated levels of hexachlorocyclohexanes (HCHs) but generally nondetectable concentrations of PBDEs. Age was shown to have a positive relationship with ΣPCBs, ΣDDTs, Σchlordanes, and total percent lipid. Contaminant levels in humpback whales were comparable to other mysticetes and lower than those found in odontocete cetaceans and pinnipeds. Although these concentrations likely do not represent a significant conservation threat, levels in the Gulf of Maine and southern California may warrant further study

Assessing persistent organic pollutant (POP) transfer from female killer whales (Orcinus orca) to calves during gestation and lactation

Persistent organic pollutants (POPs) pose a health risk for southern resident killer whales (SRKWs). Data on maternal contaminant transfer to calves are needed to inform models that estimate future contaminant loads as well as assess risk to newborn killer whale calves exposed to POPs. We conducted a study on trained female killer whales and their calves to fill these data gaps. POPs and lipid content were quantified in blood serum (POP levels in serum and blubber are highly correlated) collected during gestation and in milk and serum collected post-partum from female killer whales. Serum samples were also collected from calves during the lactation period. POP concentrations in milk collected over 15 months post-partum from the primiparous female decreased by 47-65%, depending on the contaminant class. The highest influx of contaminants to calves tended to occur soon after birth. Greater contaminant transfer rates during early lactation were also reflected in maternal serum POP levels. POP levels in maternal serum decreased significantly during the first 144-158 days post-partum, depending on contaminant class, and then leveled off through the remaining lactation period. This resulted in 67-81% reductions in POP levels in maternal serum over 15 months. By 15 months post-partum, serum POP levels from the primiparous female had dropped to levels measured in the multiparous female during pregnancy. Dissimilar to the multiparous female, body mass and blubber thickness in the primiparous female also declined significantly during the first 3-5 months post-partum, demonstrating linkages between lipid and POP transfer from blubber stores to milk in early lactation. By the end of lactation, lipid-corrected POP concentrations in serum from the first-born calf were 5-8 times greater than the corresponding POP levels from her primiparous mother. These results demonstrate that very young neonatal SRKW calves, particularly first-born calves, are at high risk from contaminant exposure

Potent phototoxicity of marine bunker oil to translucent herring embryos after prolonged weathering.

Pacific herring embryos (Clupea pallasi) spawned three months following the Cosco Busan bunker oil spill in San Francisco Bay showed high rates of late embryonic mortality in the intertidal zone at oiled sites. Dead embryos developed to the hatching stage (e.g. fully pigmented eyes) before suffering extensive tissue deterioration. In contrast, embryos incubated subtidally at oiled sites showed evidence of sublethal oil exposure (petroleum-induced cardiac toxicity) with very low rates of mortality. These field findings suggested an enhancement of oil toxicity through an interaction between oil and another environmental stressor in the intertidal zone, such as higher levels of sunlight-derived ultraviolet (UV) radiation. We tested this hypothesis by exposing herring embryos to both trace levels of weathered Cosco Busan bunker oil and sunlight, with and without protection from UV radiation. Cosco Busan oil and UV co-exposure were both necessary and sufficient to induce an acutely lethal necrotic syndrome in hatching stage embryos that closely mimicked the condition of dead embryos sampled from oiled sites. Tissue levels of known phototoxic polycyclic aromatic compounds were too low to explain the observed degree of phototoxicity, indicating the presence of other unidentified or unmeasured phototoxic compounds derived from bunker oil. These findings provide a parsimonious explanation for the unexpectedly high losses of intertidal herring spawn following the Cosco Busan spill. The chemical composition and associated toxicity of bunker oils should be more thoroughly evaluated to better understand and anticipate the ecological impacts of vessel-derived spills associated with an expanding global transportation network