At the March meeting of the Monterey Bay Chapter of the American Cetacean Society, guest speaker Doreen Moser gave a presentation on a study she conducted on harbor seals (Phoca vitulina richardsi), which inhabit coastal areas from Alaska to Baja California. Doreen's work attempted to answer questions regarding the presence of toxins found in harbor seals from four sites along the western United States. The four sites were Gray's Harbor, Washington, Umpqua River, Oregon, and two sites in California: Elkhorn Slough and the Channel Islands. In addition to her study on toxins present and their levels she investigated "red pelage," a condition that causes the hair of certain seals to turn red.
In the San Francisco area many harbor seals (up to 40% in both sexes) are afflicted with red pelage. A condition that was initially confined to animals in this area, red pelage is now found in other areas, and again, only in harbor seals. There appears to be no physiological effect on the animals. Doreen concluded that the condition is caused by an accumulation of iron on the animal's hair. At the same time that iron levels were checked an analysis was conducted on blood and blubber tissue for the presence of other trace elements and toxins. No statistical significant difference in the amount of iron was found in the tissues of animals with red pelage and normal animals. One significant observation was made, however. Using an electron microscope, Doreen discovered that the hair of red pelage animals was very high in what was described as cuticle degradation. Doreen speculates that a possible reason for one animal affected with red pelage may be that that animal has some physical property of its fur allowing iron or other elements to oxidize (or rust) on the hair.
Toxicology and trace element analysis was conducted on all animals captured or found dead at the test sites. Additionally, liver samples were extracted from dead animals. The trace elements copper, iron, selenium, and zinc were the only ones found. A number of toxic substances were tested for. The results of the study indicated that there were no significant differences in trace element levels in animals from the four sites. Also, pollutant levels were relatively low among samples at all sites.
In her presentation, Doreen covered the difficulties one encounters in setting up and carrying out a study of this type. She objectively pointed out that her study's limitations included a small sample size, poor sample composition, a low power of statistical comparison, and funding problems. Despite these limitations Doreen did an important piece of work that, combined with future work, will help answer questions about how harbor seals are affected by the presence of various elements in the ecosystem.
Click here for links to additional information about harbor seals.
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