Climate Change, Overfishing Influence Mercury Accumulation In Fish: IIT Hyderabad, Oxford Study

James Marshall
August 11, 2019

Joining hands with Harvard University, the Indian Institute of Technology-Hyderabad has found how climate change impacts mercury accumulation in fish.

Concentrations of the toxin in cod increased by up to 23 per cent between the 1970s and 2000s as a result of dietary shifts initiated by overfishing and then a recovery of herring populations, they suggested.

The Research was led from India by Dr. Asif Qureshi, Associate Professor, Department of Civil Engineering, IIT Hyderabad, and co-authored by Dr. Amina Schartup, Dr. Colin Thackray, Dr. Clifton Dassuncao, Dr. Kyle Gillespie, Dr. Alex Hanke and Dr. Elsie Sunderland.

There have been global efforts to reduce the amount of mercury entering the ocean to reduce the amount of mercury found in fish and other marine animals.

The scientists developed a first-of-its-kind, comprehensive model that simulates how environmental factors, including increasing ocean temperatures and overfishing, affect levels of methylmercury in fish. The research notes its important role in determining mercury accumulation in the fish. 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 ME recorded since 1969.

The team chose Gulf of ME, a commercially exploited, marginal sea in the north-western Atlantic Ocean for the study, however, they highlighted that mercury levels in fish in other seas and oceans are likely to have a similar relationship with sea temperature, fishing practices and mercury pollution levels.

An increase of 1 degree Celsius in seawater temperature relative to the year 2000, for example, would cause methylmercury levels in cod to rise by 32 percent and levels in spiny dogfish to rise by 70 percent.

"This study brings together different kinds of data with models in a way that will have a direct impact on how we manage fisheries", says Hedy Edmonds, a program director in NSF's Division of Ocean Sciences, which funded the research. Qureshi said that more mercury in the body can cause neurological, cardiovascular and endocrinal disorders in humans.

Bluefin tuna has also seen better days when it comes to mercury bioaccumulation according to the researchers. There was a decrease in tissue mercury levels in the ABFT between 1990 and 2012, and this was driven by a fall in sea temperature during that period.

This methylmercury, which can affect brain function, works its way up the food chain and accumulates in top predators in high concentrations.

"We need to reduce human emissions (of mercury) and the largest source in the United States presently, accounting for about 40% of emissions, is coal-fired utilities", Sunderland told the Thomson Reuters Foundation. His team will carry out further studies to assess mercury levels in humans, fish and general environment.

Other reports by Click Lancashire

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