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Elephant seal resting
A group of researchers warn that mercury pollution is serious enough to become a matter of concern since significant amounts of monomethylmercury were recently detected in the fur of elephant seal and sea lions in the North Pacific.
Mercury doesn’t naturally appear in the ocean. Researchers explained that the toxic fumes human activities release in the atmosphere and the mercury waste plants drop into the environment usually reach the open ocean. From there, some microorganisms convert it into a toxic form called monomethylmercury, which can do real damage to the brain.
And if sea creatures eat these microorganisms, the neurotoxin enters their bodies, and from them it gets transferred to the bodies of other predators and so on, until the top of the food chain. This is how we may explain the high levels of monomethylmercury found in elephant seals and sea lions: they get intoxicated from their prey.
The research team noted that there are large areas in the ocean that can be called monomethylmercury “hotspots.” Those areas need to be monitored constantly by authorities which should also prohibit seafood harvesting from those locations. Mercury-laden seafood poses a health risk especially for pregnant women and small children.
Usually, monomethylmercury reaches the shoreline because of a nearby polluter such as a chemical plant. But study authors suggest that that is no longer true. Coastal areas can be contaminated by seals and other marine mammals that can carry the toxic chemical miles away and shed it into water.
Although the idea may seem unrealistic, scientists have suspected for nearly five decades that this may explain the high levels of monomethylmercury found off the coasts. And the new research brings evidence to back the idea.
In the 1970s, high levels of mercury were detected in the mussel breeding grounds in Año Nuevo, California. Since there was no direct source of pollution nearby, researchers suspected that the chemical may have been brought to the area by seals and sea lions which were living in large numbers in the area.
Jennifer Cossaboon, lead author of the study, said that researchers in the 1970s came up with the idea but they couldn’t back it with hard evidence because they didn’t have the necessary tools to do it.
But Cossaboon’s team had the necessary technology and returned to Año Nuevo to see whether the old theory still stands. They took water samples from the mussel breeding grounds and fur samples from the nearby elephant seals. The levels of mercury were higher than in any other coastal part of California, the team noted. To be more precise, they were eight times higher. So, scientists suspected that the seals may have something to do with it.
Researchers also found high amounts of mercury in the animals’ fur, and discovered a spike in mercury levels during the molting season, when the seals shed their fur.
Image Source: Wikimedia
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