Abstract

The slow population recovery of the endangered Steller sea lion (SSL, Eumetopias jubatus) and continuing decline in the western Aleutian Islands may be a result of multiple factors.¹ Recent publications have reported relatively high concentrations of mercury ([Hg]) that may result in adverse health effects in seals.^2,3 Studies have shown high [Hg] leads to endocrine disruption.^4,5,6 Considering these previous findings, further investigation is warranted on the potential impact of Hg on the health and development of young SSLs, an age group particularly at risk of these effects in part due to in utero exposure. Hair is a versatile tissue with proven use monitoring total [Hg] and stable isotopes of carbon and nitrogen. Unlike serum, hair is relatively biochemically stable once hormones are deposited during growth, eliminating the impact of capture and handling stress on the results. We assessed the relationship between adrenal hormone concentrations (cortisol and aldosterone) and sex, location, body mass, and hair [Hg] in SSL pups sampled on their natal rookery. Hair was collected from a patch lateral to the spine and dorsal to the rear flipper insertion on the right side of SSL pups on 4 rookeries during June/July 2017. Samples were washed in 1% Triton X-100, rinsed with ultrapure water, and freeze dried. For hormone analysis, 20 mg of hair was ground with a Retsch MM 400 Miser Mill (Retsch Inc) and 1 mL of 100% methanol was added and samples were rotated slowly for 24 hours to extract the hormones.⁷ Samples were then centrifuged, and the supernatant collected and frozen. Enzyme immunoassay kits were used for measuring aldosterone and cortisol (Arbor Assay, Ann Arbor MI). For [Hg], prepared hair samples were analyzed using a Milestone Scientific direct mercury analyzer (DMA-80) following methods from Castellini et al. (2012). Cortisol (2.4–113.7 pg/mg) and aldosterone (0.2–28.0 pg/mg) was measurable in all hair samples from young SSL pups that were <2 months old (N=195). Given the pups age and time of collection, all hair samples were grown in utero providing information on both the condition of the adult female during late gestation and the developing SSL pups. Male pups were larger than females and mass (20.8–50.8 kg) and standard length (94.0–121.0 cm) significantly differed between the four rookeries (P<0.05), with pups from Agatuu Island being smaller. Mean cortisol concentrations were significantly different by rookery and associated with mass (P<0.05). There was no significant difference in hormone concentrations between sexes. Log aldosterone concentrations were significantly different between rookeries (P<0.05) with samples from Ulak Island having higher aldosterone concentrations (7.5±5.8 pg/mg, N=47) than pups from other sites (2.5±2.3 pg/mg, N=148). The measurement of [Hg] in the hair of these SSLs is currently being completed and will be compared to the hormone results. These results indicate the ability of using hair to measure adrenal hormones from SSL pups and additional sampling and analyses of hair may have important implications toward the management and recovery of SSL populations.

Acknowledgements

This work was supported by grant NA16NMF4390029 and sample collection was under MMPA permits 18528 and 18537 and ADF&G ACUC Protocol 2016-39. We would like to thank Dr. Tom Gelatt and the field team from the Marine Mammal Laboratory Alaska Ecosystems Program for assistance with sample collection. We are grateful for the crew of the research vessel M/V Tiglax, Drs. Colleen Duncan and Lesanna Lahner for veterinary support during field efforts and the laboratory assistance from Claire Squires and Ross Dorendorf from Alaska Dept. of Fish and Game for sample preparation.

* Presenting author
+ Student presenter

Literature Cited

1.  Fritz, L. W., R. Towell, T. S. Gelatt, D. S. Johnson, and T. R. Loughlin. 2014. Recent increases in survival of western Steller sea lions in Alaska and implications for recovery. Endangered Species Research. 26:13–24.

2.  Castellini, J. M., L. D. Rea, C. L. Lieske, K. B. Beckmen, B. S. Fadely, J. M. Maniscalco, and T. M. O’Hara. 2012. Mercury concentrations in hair from neonatal and juvenile Steller sea lions (Eumetopias jubatus): Implications based on age and region in this Northern Pacific marine sentinel piscivore. EcoHealth. 9:267–277.

3.  Iwata, H., M. Watanabe, Y. Okajima, S. Tanabe, M. Amano, N. Miyazaki, and E. A. Petrov. 2004. Toxicokinetics of PCDD, PCDF, and coplanar PCB congeners in Baikal seals, Pusa sibirica: age-related accumulation, maternal transfer, and hepatic sequestration. Environmental Science & Technology. 38:3505–3513.

4.  Freeman, H., G. Sangalang, J. Uthe, and K. Ronald. 1974. Steroidogenesis in vitro in the harp seal (Pagophilus groenlandicus) without and with methyl mercury treatment in vivo. Environmental Physiology & Biochemistry. 5:428–439.

5.  Freeman, H. C. and G. B. Sangalang. 1977. A study of of the effects of methyl mercury, cadmium, arsenic, selenium and a PCB, (Aroclor 1254) on adrenal and testicular steroidogenses in vitro, by the gray seal Halichoerus grypus. Archives of Environmental Contamination and Toxicology. 5:369–383.

6.  Tan, S. W., J. C. Meiller, and K. R. Mahaffey. 2009. The endocrine effects of mercury in humans and wildlife. Critical Reviews in Toxicology. 39:228–269.

7.  Keogh, M.J., S.A. Karpovich. 2016. Validation of hair as a novel tissue for assessing adrenal hormones in young Steller sea lions (Eumetopias jubatus). Alaska Marine Science Symposium.