Toxic mercury levels in fish increase despite reduced emissions efforts

Toxic mercury levels in fish increase despite reduced emissions efforts
Photo: Unsplash

Research suggests that climate change and overfishing are hindering efforts to reduce the accumulation of toxic mercury in seafood. While worldwide mercury emissions have decreased, warmer ocean waters and unbalanced ecosystems due to overfishing is altering mercury buildup in fish and shellfish.

A team of scientists found increased methylmercury in sample tissues taken from Atlantic cod (Gadus morhua) fished from the Gulf of Maine. Their new study reveals an increase of around 23 percent over an estimated 30-year period. Despite the reported decrease in atmospheric mercury levels observed over the same time span (the 1970s to 2000s). Findings reveal that the cod’s diet has been affected by overfishing herring in the past. The research notes its important role in determining mercury accumulation in the fish.

Bluefin tuna has also seen better days when it comes to mercury bioaccumulation according to the researchers. The team created simulations to measure the effects of warming seawater on the fish, incorporating emission and temperature changes as well as mercury levels in bluefin tuna captured from the Gulf of Maine recorded since 1969. Results from the simulations reveal that as seawater temperature increases, it could be behind around a 56 percent increase in methylmercury found in the fish.

One of the study’s authors Elsie Sunderland an environmental chemist from Harvard University says, “This is really the first investigation to look at migratory marine fish and the potential impacts of temperature and overfishing”. Sunderland says that before this research, scientists have only considered atmospheric mercury levels when it comes to the chemical’s concentration in seafood while some factors are overlooked.

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