Marine Toxicology
Sea Lion Photo courtesy of Mystic Aquarium
Background
The western population of the Alaskan Steller sea lion is and continuing to decline for unknown reasons. One potential explanation for the sea lion's decline is environmental contamination. Steller sea lions are exposed to a variety of contaminants, including metals, through their environment and diet, and indeed, preliminary studies indicate that Steller sea lions bioaccumulate aluminum, copper, mercury, vanadium, and silver (1, 2, 3).
However, while these studies clearly show that Steller sea lions are exposed to metals, they don't document the extent of exposure or bioaccumulation. This is because those studies were limited either by the number of metals considered or the number of organs considered. For example, one study looked at several metals, but only in liver (1). A second examined many organs, but only three metals and the third only looked at several metals and only 1 organ (2, 3). As a result, our understanding of metal bioaccumulation in Steller sea lions is very uncertain. It is very possible that some of these metals are at dangerously high levels in other untested organs.
The Wise Laboratory of Environmental and Genetic Toxicology is investigating the role of contaminants as environmental factors in this decline.
Experimental Studies
Steller Sea Lion Cells
We are focusing on metals, measuring their accumulation in the tissues of the sea lions, establishing cell lines from the major organ systems and determining the effects of metals in these lines, so that a priority list can be developed for intervention measures.
We have created cell lines of several organs and are testing them to determine how much of a metal is required to cause cell death and damage chromosomes to help us further understand and predict potential threats to the Steller sea lion. In addition, these cell lines will allow for more detailed biochemical and physiological studies of Steller sea lion biology, which will aid in maintaining the health of this population. Finally, the cell lines will serve as a model of sea lions and marine mammals in general and allow for comparisons with data in human cells to determine similarities and differences between humans and marine mammals.
The data generated so far indicate a clear difference in response depending on the organ and metal considered (See Figures below). In particular, testes appear to be the most sensitive tissue. Chromium and arsenic appear to be two of the more potent cytotoxic metals.
This figure shows the cytotoxicity of chromium in cells from 3 Steller sea lion organs including bronchus (yellow line), dermis (orange line), and testes (red line). The results indicate that testes are the most sensitive to chromium and dermis the more resistant, with bronchus in between. Thus it is important to consider each organ independently when assessing the effects of a chemical on an animal.
This figure shows the cytotoxicity in Steller sea lion dermal cells of 4 metals including chromium (yellow line), mercury (purple line), cadmium (blue line), and arsenic (green line). The results indicate that arsenic and chromium are the most cytotoxic to dermal cells and cadmium, the least. Thus it is important to consider each chemical independently when assessing the effects of chemicals on an animal.
References
- Sydeman, W.J., and Jarman, W.M. Trace Metals in Seabirds, Steller Sea Lion and Forage Fish and Zooplankton from Central California. Marine Pollution Bulletin 36: 828-832. 1998.
- Saeki K., Nakajima M. Loughlin T.R., Calkins, D.C., Baba N., Kiyota M., and Tatsukawa R. Accumulation of silver in the liver of three species of pinnipeds. Environmental Pollution 112:19-25, 2001.
- Saeki K, Nakajima M., Noda K., Loughlin T R., Baba N., Kiyota M., Tatsukawa R., and Calkins D.G. (1999) Vanadium accumulation in pinnipeds. Archives Environmental Contamination Toxicology 36:81-86, 1999.
Relevant Wise Laboratory Publications
Wise, Sr., J.P., Goertz, C.E.C., Wise, S.S., Morin, A.T., Dunn, J.L., Gulland, F.M.D., Bozza, M., Atkinson, S., and Thompson, W.D. Chromium Cytotoxicity in Steller Sea Lion Lung, Skin and Testes Cells. In Trites, A.W., Atkinson, S.K., DeMaster, D.P., Fritz, L.W., Gelatt, T.S., Rea, L.D., and Wynne, K.M. (Eds), Sea Lions of the World Conservation and Research in the 21st Century. Alaska Sea Grant College Program, pp. 57-68, 2006.
Collaborators and Cooperators
The Wise Laboratory is assisted in this work by an important number of collaborators and cooperators. In particular, the following prominent scientists and their teams provide significant support and input:
Dr. AbouEl-Makarim Aboueissa is an Assistant Professor of Mathematics and Statistics at the University of Southern Maine (USM). He provides statistical expertise particularly in the area of handling samples with measurements at or below detection limits.
Dr. Shannon Atkinson is the Research Director of the Alaska SeaLife Center in Seward, Alaska. She provides advice and guidance on Steller sea lions.
Dr. J. Lawrence Dunn is the Staff Veterinarian at the Mystic Aquarium. He provides expert advice and guidance in marine mammal pathobiology, endocrinology, parisitology and virology.
Dr. Frances Gulland is the Director of Veterinary Service at the Marine Mammal Center in Sausalito, California. She provides expert advice and guidance on marine mammals and tissue from a variety of Western species.
Dr. Yawei Zhang is an Assistant Professor of Epidemiology and Public Health at Yale University. She provides expert advice and guidance on the statistical analysis and epidemiological design of marine mammal studies.
Dr. Tongzhang Zheng is Professor of Epidemiology and Public Health and Head of the Environmental Health Sciences Division at Yale University. He provides expert advice and guidance on the statistical analysis and epidemiological design of marine mammal studies.
Funding
This work was generously supported by grant NA03NMF4390041, "Metal toxicity in Steller Seal Lion (Eumetopias jubatus) Tissues and Cell Lines", from the National Oceanic and Atmospheric Administration and by the Maine Center for Toxicology and Environmental Health.
