Climate Change May Trigger Higher Mercury Levels in Fish, Study Suggests

Adding to the extensive list of climate change's effects, researchers from Dartmouth College have uncovered a link between rising ocean surface temperatures -- a result, they say, of a changing climate -- and the amount of mercury in fish.

High in protein and omega-3 fatty acids, fish can play an important role in promoting proper growth and development as well as heart health. However, tucked away in the fatty tissue of many kinds of fish are high levels of methylmercury, an even more toxic form of mercury that has been altered by bacteria.

According to the National Institute of Health, unborn babies and young infants are especially sensitive to the effects of methylmercury, which includes damage to the central nervous system.

Research has shown that mercury released into the air in the form of industrial pollution accumulates in bodies of water where it is converted into methylmercury.

When it comes to the relationship between global warming and the bioaccumulation of methylmercury in marine life, however, science is largely a blank slate, with no previous study demonstrating the effects in both lab and field experiments.

In the new report published in the journal PLOS One, Dartmouth researchers examined killifish under a range of temperatures both in the lab an in salt marsh pools in Maine. The lab fish were fed mercury-enriched food while the marsh fish ate insects, worms and other natural food sources.

In doing so, the scientists found that fish in warmer waters ate more but grew less. They also exhibited higher methylmercury levels in their tissues -- a finding that suggested increases in metabolic rates prompted the increased uptake of the toxic metal.

The Food and Drug Administration recommends that pregnant and nursing women avoid fish that may contain unsafe levels of methylmercury, including swordfish, king mackerel, shark or tilefish. Young infants should avoid these types of fish as well.