Elephant Seals Molt Accumulated Mercury Into The Ocean

A study suggests that seasonal spikes in methylmercury levels in the waters off Northern California may be caused by mercury-contaminated northern elephant seal fur (Proc. Natl. Acad. Sci. USA 2015, DOI: 10.1073/pnas.1506520112). Jennifer M. Cossaboon, Priya M. Ganguli, and A. Russell Flegal of the University of California, Santa Cruz, say this is a previously unrecognized transport mechanism for oceanic methyl­mercury. Neurotoxic methylmercury is a persistent pollutant that becomes increasingly concentrated in animals moving up the food chain. Scientists have long observed hot spots of oceanic methylmercury contamination near industrial sites, but not at Año Nuevo State Park near Santa Cruz. Thousands of elephant seals, which can be 14 feet long and weigh up to 5,000 lb, make a biannual pilgrimage to Año Nuevo. During the spring and summer months, they mate and give birth. In the winter, they shed their skin and hair in a mass molting. The researchers measured high levels of methylmercury in the molted material. Additionally, they found that methylmercury levels in the waters off Año Nuevo were greater than nearby coastal sites and spiked during the molting period.