Climate Change May Increase Mercury Content in Fish
Mercury pollution can be a serious health threat as once mercury enters our body, it acts as a neurotoxin, interfering with the brain and nervous system. Mercury is emitted to the air by power plants and other industrial facilities and becomes a serious threat when it settles into oceans. As the mercury enters waterways, naturally occurring bacteria absorb it and the pollutant makes it way up the food chain as larger fish consume smaller fish. As an example, mackerel, swordfish, tuna, and grouper rank high when it comes to mercury content. We have known about the effects of mercury in fish for some time now, however, looming changes in climate could make fish accumulate even more mercury, according to a study in the journal PLOS ONE.
Researchers at Dartmouth College studied killifish under varying temperatures in the lab and in salt marsh pools in Maine. Fish in the marshes ate insects, worms and other natural food sources, while the lab fish were fed mercury-enriched food. Results showed the fish in warmer waters ate more but grew less and had higher methylmercury levels in their tissues, suggesting increases in their metabolic rate caused the increased uptake of the toxic metal.
Besides the warming of the water, the paper states that physical factors including wind flows, atmospheric circulation, and precipitation, will also affect mercury deposition and bioavailability.
Until now, little has been known about how global warming may affect mercury bioaccumulation in marine life, and no previous study has demonstrated the effects using fish in both laboratory and field experiments.
The paper suggests that the increase in mercury bioaccumulation at lower trophic levels can be propagated to higher trophic level fish which is consumed by humans. This increases human exposure to these dangerous concentrations. As a result, the paper urges that this effect should be incorporated into policy and management efforts aimed at reducing human health risks from high-level mercury exposure.
Read the study at PLOS ONE.
Fish image via Shutterstock.