HYDERABAD: Climate change and overfishing are resulting in an increase of a toxin called methylmercury (MeHg) in the ocean’s fishes, according to a study conducted by researchers from Harvard University and IIT Hyderabad.
Methylmercury can cause severe damage to the nervous system in humans. It occurs in sea, ocean and river water after mercury emitted from various polluting sources, mainly thermal power plants, enters the water and gets converted to methylmercury, after which it enters the fishes.
Using data collected over the last 30 years and ecosystem modelling, the team of researchers from Harvard University and IIT Hyderabad studied the trend of methylmercury presence in two predatory fishes from the Gulf of Maine in the Atlantic Ocean which are widely consumed by people — Atlantic Cod and Atlantic Bluefin Tuna.
They found that the methylmercury concentrations in the Atlantic cod increased by up to 23 per cent between 1970s to 2000s, whereas a rise of 56 per cent was estimated in the methylmercury concentration of Atlantic bluefin tuna.
In the case of Atlantic cod, change in its diet has been pointed as a reason due to over-fishing of its favoured prey like small herring and sardines and in case of the Atlantic bluefin tuna, increasing temperatures of the seawater have been blamed for the rise in methylmercury concentrations.
This rise in methylmercury concentrations occurred despite the fact that there has been a decline in the global mercury concentrations over the years and the study warrants that the mercury levels be kept under control in future too.
Dr Asif Qureshi, Associate Professor at IIT Hyderabad, one of the co-authors of the study said, “Regulatory efforts must not only control the release of mercury into the atmosphere but also significantly reduce greenhouse gas emissions that lead to seawater warming. Only by tackling both mercury emissions and global warming, can we reduce levels of mercury in marine animals and our exposure to mercury in seafood.”
Can affect the nervous system of babies
According to the World Health Organisation (WHO), methylmercury exposure in the womb through a mother’s consumption of fish can adversely affect the growing brain of a foetus growing brain and the nervous system