From UPSC perspective, the following things are important :
Prelims level : Methylmercury - water pollution
Mains level : climate change impact
Despite a decrease in seawater concentration of methylmercury since the late 1990s, the amount of toxin that gets accumulated in certain fish which are higher in the food chain have been found to increase.
- The amount of methylmercury in fish higher in the food chain can change due to two reasons — ocean warming and dietary shifts due to overfishing by humans.
- Researchers have found that there has been an up to 23% increase in methylmercury concentration in Atlantic codfish in the Gulf of Maine in the northwestern Atlantic Ocean.
- The increase in the methylmercury concentration in codfish has been due to changes in the diet caused by overfishing.
- As a result of diet change, cod fish in the 2000s relied more on larger herring and lobster, which have higher concentrations of the toxin than other prey fish consumed in the 1970s.
- Besides dietary changes, ocean warming too causes changes in the methylmercury accumulation in fish.
- Fish metabolism is temperature-dependent. So as ocean temperature increases, fish experience higher metabolism and more energy obtained from food is spent on maintenance rather than growth, leading to more methylmercury getting concentrated in predatory fish.
The researchers warn that human exposure to the toxin through fish consumption is bound to increase as a result of climate change. Hence, there is a need for stronger regulations to protect ecosystem and human health.