Steep Rise in Ocean Mercury

Mercury levels in the Pacific Ocean have risen by 30 percent in the past 20 years and are expected to increase by 50 percent in the next few decades as emissions from power plants and other industrial sources rise, according to a new study. Scientists from Harvard University and the U.S. Geological Survey discovered the increases after sampling mercury levels at 16 locations in the Pacific Ocean and comparing them with historical data, according to the study, published in the journal Global Biogeochemical Cycles. The mercury eventually settles in large predatory fish, such as tuna, and can cause neurological and other health problems in people who consume large quantities of fish. The study also documented for the first time how mercury emitted from coal-fired power plants and other industrial sources winds up in fish. The researchers determined that the mercury is absorbed by algae that filters down to mid-ocean depths of 200 to 700 meters, where the algae is decomposed by bacteria and the industrial mercury is “methylated” and transformed into methylmercury, a neurotoxin. The methylmercury then moves up the food chain from phytoplankton, to zooplankton, to fish.