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Mon Nov 11, 2019, 07:52 AM

Climate change and overfishing are boosting toxic mercury levels in fish

Source: The Conversation

Link: http://theconversation.com/climate-change-and-overfishing-are-boosting-toxic-mercury-levels-in-fish-122748

Excerpt:

We live in an era — the Anthropocene — where humans and societies are reshaping and changing ecosystems. Pollution, human-made climate change and overfishing have all altered marine life and ocean food webs.

Increasing ocean temperatures are amplifying the accumulation of neurotoxic contaminants such as organic mercury (methylmercury) in some marine life. This especially affects top predators including marine mammals such as fish-eating killer whales that strongly rely on large fish as seafood for energy.

Now the combination of mercury pollution, climate change and overfishing are conspiring together to further contaminate marine life and food webs. This has obvious implications for ecosystems and the ocean, but also for public health. The risk of consuming mercury-contaminated fish and seafood is growing with climate change.

Mercury rising
Regulations have lowered global mercury emissions from human-made sources, such as coal-fired power plants, between 1990 and 2010 but mercury is still present in the marine environment.

Methylmercury builds up in the muscle tissue of fish across the food web, “bioaccumulating” in larger and high trophic level predators. This is why larger pelagic fish (for example, tuna, marlins, billfishes and sharks) — those that eat a lot of fish — are in general considered riskier to eat than smaller ones.

In humans, mercury can lead to neurological disorders. Children who are exposed to mercury during fetal development and childhood have a greater risk of poor performance on tests that measure attention, IQ, fine motor function and language.

Climate change can amplify the accumulation of methylmercury in fish and marine mammals at the top of their food webs due to changes in the entry and fate of mercury in the ocean and the composition and structure of these marine food webs. A warmer and more acidic ocean may increase the amount of methylmercury that enters the food web.

Overfishing can also exacerbate the mercury levels in some fish species. Pacific salmon, squid and forage fish, as well as Atlantic bluefin tuna and Atlantic cod and other fish species are susceptible to increases in methylmercury due to rising ocean temperatures.


Random thought: Have any scientists looked into the effect of mercury on the animals that live in the ocean? If consuming mercury is bad for humans and can even damage our minds and bodies, what is it doing to dolphins, various fish, whales and so forth? Is it affecting them? Could it explain self-beaching or sea mammals becoming disoriented or not eating, etc...? I'll google this later, but I've never seen an article on it.

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