Regional variations and drivers of mercury and selenium concentrations in Steller sea lions.

Mercury (Hg) can be neurotoxic to mammals and impact reproduction, whereas selenium (Se) is an important antioxidant known to ameliorate some adverse effects of Hg. Total Hg concentrations ([THg]) were measured in lanugo (pelage grown in utero) of 812 Steller sea lion (Eumetopias jubatus) pups across Alaska and Russia to assess fetal exposure during late gestation. The molar ratio of total Se to THg (TSe:THg) was determined in whole blood collected from 291 pups. Stable isotope ratios of carbon and nitrogen were measured in sections of vibrissae (whiskers, n = 498) and in lanugo (n = 480) of pups grown during late gestation to track diet variations among adult females that can drive Hg and Se exposure during this critical fetal development period. Lanugo [THg] ranged from 1.4 to 73.7 µg/g dry weight with the lowest median [THg] in Southeast Alaska. Pups from the Western Aleutian Islands had higher median lanugo [THg] than pups from other metapopulations in Alaska. Over 25% of pups in the Western Aleutian Islands had [THg] above published risk thresholds (20 µg/g) for other mammals. Whole blood molar TSe:THg was significantly lower in the Western Aleutian Islands and in some parts of the Central Aleutian Islands with higher molar ratios found in the Eastern Aleutian Islands and Central Gulf of Alaska. This suggests a limitation on potential protective functions of Se in the western regions with the highest relative [THg]. The Central Aleutian Island pups with [THg] over 20 µg/g had higher δ15N ratios than pups with lower [THg] suggesting dams consuming higher trophic level prey is a key driver for Hg exposure. However, regional differences likely reflect variability in diet of the dam during gestation and in Hg food web dynamics between oceanic regimes east and west of key passes in the Aleutian Islands.

Viral emergence in marine mammals in the North Pacific may be linked to Arctic sea ice reduction.

Climate change-driven alterations in Arctic environments can influence habitat availability, species distributions and interactions, and the breeding, foraging, and health of marine mammals. Phocine distemper virus (PDV), which has caused extensive mortality in Atlantic seals, was confirmed in sea otters in the North Pacific Ocean in 2004, raising the question of whether reductions in sea ice could increase contact between Arctic and sub-Arctic marine mammals and lead to viral transmission across the Arctic Ocean. Using data on PDV exposure and infection and animal movement in sympatric seal, sea lion, and sea otter species sampled in the North Pacific Ocean from 2001-2016, we investigated the timing of PDV introduction, risk factors associated with PDV emergence, and patterns of transmission following introduction. We identified widespread exposure to and infection with PDV across the North Pacific Ocean beginning in 2003 with a second peak of PDV exposure and infection in 2009; viral transmission across sympatric marine mammal species; and association of PDV exposure and infection with reductions in Arctic sea ice extent. Peaks of PDV exposure and infection following 2003 may reflect additional viral introductions among the diverse marine mammals in the North Pacific Ocean linked to change in Arctic sea ice extent.

[Composition and distribution of the mitochondrial lineages of gray whales (Eschirichtius robustus) in the far eastern seas of Russia].

The frequency of occurrence of the mitotypes (control region, cytochrome b gene, and DN2 gene) has been studied for groups of gray whales feeding and growing along Chukotka Peninsula, Koryak Coast, eastern Kamchatka, and Sakhalin Island. The number of the mitotypes decreased dramatically from the northern waters southwards; however, the dominant mitotypes remained the same. Both mitochondrial lineages known for this species might be found for the whales gathering in the reproductive area along the Californian Coast in accordance with the comparison of the published and original data on the haplotypes of the control region. However, it has also been argued that similar sequences of the control region might be found in different mitochondrial genomes, and the analysis of only this site of mtDNA might lead to incorrect conclusions.

Serum chemistry values of free-ranging, lactating northern fur seals (Callorhinus ursinus).

Reference range clinical serum chemistry values were established for free-ranging lactating northern fur seals (Callorhinus ursinus). Fur seals sampled for this study were part of a healthy and growing population in the Kuril Islands of far-east Russia. Blood was collected from 45 females between June and August 2005 to 2007. Fresh serum was assayed for 16 components. Packed-cell volume was determined from fresh whole blood. Results are made available for future comparisons with the declining population of northern fur seals on the Pribilof Islands and are compared with published values for other otariid species.

[Detection of specific antibodies to morbilliviruses, Toxoplasma, and Brucella species in eared seals in North-West of Pacific Ocean].

Presence of antibodies to morbilliviruses, Toxoplasma, and Brucella species in eared seals in North-West of Pacific Ocean was studied. Sera from 189 cubs of eared seals from different rookeries and regions. It has been shown that 10-22% of cubs living on Russian coast have antibodies to such dangerous diseases as morbillivirus infection, brucellosis, and toxoplasmosis. Antibodies to the two pathogens were detected in several animals, and brucellosis was more frequently detected associated infection. These results confirm hypothesis that all 3 pathogens are enzootic in eared seals population.