Researchers from the University of California - Santa Cruz found that Elephant seals are not only a bioindicator for their environment but a significant source for methylmercury themselves. Methylmercury, previously taken up by the animals is returned to the water with the seals’ excreta and fur during the molting season, which contributes to the high levels of mercury in the in coastal waters near the elephant seal rookery at Año Nuevo State Reserve.
"Many studies have looked at biomagnification up the food chain, and we took that a step further to see what happens next. Mercury is an element, so it never breaks down and goes away -- it just changes forms," Jennifer Cossaboon, first author and graduate student in environmental health at San Diego State University, said in a news release. “Elephant seals undergo a catastrophic moult (which) comes off in big sheets of fur and the top few layers of skin”, explaines Jennifer Cossaboon.
A 1981 study by coauthor Russell Flegal, professor of microbiology and environmental toxicology at UC Santa Cruz, had found elevated mercury concentrations in mussels near large colonies of seals and sea lions at Año Nuevo and San Miguel Island.
"At that time, we didn't have the analytical instruments to detect mercury at the concentrations found in seawater, so we used mussels, which filter seawater, as sentinel organisms," Flegal said. "In the new study, we were able to look at seasonal changes in the water, and during the elephant seal molting season the levels of methyl mercury really took off."
Compared to other coastal sites, the concentration of methyl mercury in the seawater at Año Nuevo was twice as high during the breeding season and 17 times higher during the molting season.
Source: Press release University of California - Santa Cruz
from Sep. 7, 2015 The original study
Jennifer M. Cossaboon, Priya M. Ganguli, A. Russell Flegal, Mercury offloaded in Northern elephant seal hair affects coastal seawater surrounding rookery
, Proc. Nat. Acad. Sci. USA, 2015: doi: 10.1073/pnas.1506520112
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