In recent years, more and more species of fish show signs of high levels of methylmercury, which can be toxic for people that consume them. Experts have been trying to find out why this is happening, but now Harvard University researchers might have the answer.
Methylmercury is created when mercury comes in contact with different types of bacteria. People get intoxicated with this substance after eating fish and seafood, since many species ingest methylmercury. Exposure to this substance has always caused concerns. But now the levels of toxicity seem to be increasing worldwide.
According to statistics, 82% of people intoxicated with methylmercury in the U.S. were exposed to it after eating fish. A new study, conducted by Harvard scientists and published in the journal Nature, offers evidence that levels of methylmercury in seafood are increasing. Even more, scientists believe the main cause of this phenomenon is global climate change.
Climate change causes a high level of toxic substances in seafood
To reach these results, the experts analyzed 30 years worth of data accumulated on the Gulf of Maine in the Atlantic Ocean. Furthermore, they studied the diets of the Atlantic cod and the spiny dogfish from the 1970s to 2000s. As it turns out, levels of methylmercury decreased by 6-20% in cod and increased by 33-61% in spiny dogfish.
The difference was explained by analyzing the diets of the two species. In the 70s, the main source of food for both species was herring, but the population decreased at the time, so the two predators had to turn to different foods. While cod primarily eats shads and sardines, spiny dogfish prey on squid and other cephalopods. It is known that smaller fish have lower levels of the toxic substance, so it explains why levels of methylmercury decreased in cod.
After the year 2000, the herring population came back to normal levels, so cod methylmercury levels increased again, while dogfish methylmercury levels decreased.