The study, published this week in Nature, is the first to create a comprehensive overview of the mercury in the ocean. The study also determined where the mercury was coming from, finding that human activities, including burning fossil fuels like coal, and mining for gold and coal, are the main drivers for the increase in the ocean’s mercury, causing the substance to increase by a factor of 3.4 in the ocean’s upper levels since the Industrial Revolution started.
The research team figured out the mercury’s relationship to human activities by comparing it to the well-documented levels of CO2 over the last few decades. The researchers found that the ratio of added mercury to added CO2 stays about the same in the ocean, so by using data of how much CO2 is in the ocean, they were able to estimate how much mercury has been added over the last several decades.
Because the increase in mercury is driven by human activities — settling into the ocean from air pollution or being carried via streams and rivers — the upper 100 meters (328 feet) of the ocean is the region that’s most quickly accumulating the dangerous element. But the increase in the ocean’s surface levels means that, as humans emit more mercury, the deep ocean is going to be less and less able to store the mercury, study co-author Carl Lamborg told Nature.
“You’re starting to overwhelm the ability of deep water formation to hide some of that mercury from us, with the net result that more and more of our emissions will be found in progressively shallower water,” he said. Lamborg also said that, at the rate humans are going now, we’re projected to emit as much mercury in the next 50 years as they did in the last 150 years.
Mercury is a neurotoxin, and ingesting too much of it can cause developmental defects in fetuses and, at extreme levels, death. Typically, people ingest mercury through eating fish, with larger, predatory fish containing more mercury than smaller prey fish. Right now, the scientists aren’t sure how these increased levels of mercury affect the health of ocean fish or the health of people consuming them
“I would not stop eating ocean fish as a result of this,” Simon Boxall, lecturer on ocean and Earth science at the University of Southampton, told the Guardian. “But it is a good indicator of how much impact we are having on the marine environment. It is an alarm call for the future.”
Mercury Levels in the Ocean Are Now 3 Times Higher Than Before the Industrial Revolution
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