California coasts are now tainted with a toxic compound of mercury because of an unexpected source – molting elephant seals.
Until now mercury spills in the waterways and toxic emissions in the atmosphere were the two major sources of mercury pollution in North Pacific. But California researchers had a feeling that it was more to it than that since the 1970s. They, however, lacked the necessary evidence to prove that elephant seals and sea lions were also responsible for shoreline mercury pollution.
Researchers explained that when mercury reaches the ocean, bacteria turn the chemical into a more dangerous compound called methylmercury, which is later eaten by fish and other sea creatures and eventually contaminate animals in the higher layers of the food chain including seal lions and elephant seals.
But as these animals enter the molting season, their mercury-laden fur contributes to the high levels of mercury off California coasts. Methylmercury is also very toxic to the brain of any animal and can kill small sea creatures if a certain limit is passed.
The research team noted that they have found hotspots of the toxic compound in several areas of the Pacific and they urged authorities to take steps to prevent fishermen and companies from harvesting seafood in those areas. Mercury-tainted seafood is especially harmful to pregnant women and small children.
In most cases, when methylmercury is reported in one area, there is a source of pollution nearby such as a chemical plant. But in some coastal areas no such sources are visible and the mercury pollution levels are still high. The team learned that the mercury is carried from deep sea to the coastal areas by elephant lions through their shed fur.
Although the scenario is hard to believe, scientists came up this theory first in the 1970s when high levels of mercury pollution were recorded in mussel breeding grounds in Año Nuevo, Calif.
But the area is also filled with sea lions and elephant seals. So, the researchers had the idea that “material” resulted from the animals was getting methylmercury into the system. On the other hand, because researchers had no instruments to measure the levels of mercury in those animals, they weren’t quite sure what type of material was responsible for the pollution.
Several decades later, scientists have the technology and used it on the seals in Año Nuevo. They learned that mercury pollution in the area was significantly higher than in other California coastal regions. Additionally, mercury pollution spiked every year when elephant seals entered molting season.
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