Climate change turning marine life toxic

Toxic mercury in fish rising with climate change and overfishing - The Jakarta Post

Toxic mercury in fish rising with climate change and overfishing - The Jakarta Post

Add another item to the ever-growing list of the risky impacts of climate change: Warming oceans are leading to an increase of the harmful neurotoxicant methylmercury in popular seafood, including cod, Atlantic bluefin tuna and swordfish, according to research led by researchers at Harvard University.

Using this understanding, the researchers also modelled the mercury levels found in Atlantic BlueFin Tuna (ABFT).

The researchers focused on whether have these and other environmental measures alleviated or overall exacerbated the problem of elevated mercury levels in fish. 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. This means that larger, more predatory organisms that sit at the top of the food chain will have higher levels of methylmercury than the organisms that they eat, which scientists have known for a long time. But this doesn't entirely account for the recent increase in methylmercury levels.It also has to do with fishes' size and speed, as well as their changing environment.

The researchers found that warming oceans resulting from climate change cause fish to expend more energy when they swim, which in turn causes them to burn more calories. They used three decades of data on the ecosystem and mercury concentrations and developed a model for mercury bioaccumulation. Highlighting the significance of these observations, Qureshi said although the study was carried in the Atlantic Ocean, mercury levels in fish in other seas and oceans too are likely to have a similar relationship with sea temperature, fishing practices and mercury pollution levels.

"Being able to predict the future of mercury levels in fish has been hard to answer because, until now, we didn't have a good understanding of why methylmercury levels were so high in big fish", said Amina Schartup, first author of the paper.

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Around four-fifths of the mercury put into the atmosphere from natural and human causes, such as burning coal, ends up in the ocean where some is converted by tiny organisms to a particularly unsafe form known as methylmercury.

More than three billion people rely on seafood for nutrition and the findings have raised serious concern over impact on human health, especially those in the coastal areas.

Even with a 20 per cent decrease in methylmercury in sea water as a outcome of reductions in emissions, a 1C temperature rise would lead to increases of 10% in cod and 20 per cent in spiny dogfish, the researchers said.

Marine life accumulate methylmercury, in part, from the inorganic mercury that collects in the atmosphere from natural and human source.

The study showed that despite a decrease in global mercury emissions since late 1990s, MeHg concentration in fishes like Atlantic cod, Atlantic bluefin tuna, which are widely consumed by humans, has actually increased. "We can all agree less methylmercury in these fish in the future would be a good thing".

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