Climate Change Mitigation: Added Costs of Clean Energy

Harvard University researchers have recently been able to explain why concentrations of the potent neurotoxin, Methylmercury, are high in Arctic marine life. They suggest that global warming and melting sea-ice in the Arctic and sub-Arctic regions yield high levels of this toxin.

Hydroelectric power is used to curb global warming in some areas, but flooding for this renewable energy could put even more methylmercury into ecosystems than climate change originally, according to a release.

"Clean energy benefits the entire world, but the costs of hydroelectric power are often assumed entirely by the Aboriginal communities who live next to these developments," Elsie Sunderland, associate professor of environmental engineering at the Harvard John A. Paulson School of Engineering and Applied Science (SEAS) and environmental health at the Harvard Chan School, said in a news release. "Our research highlights some of the costs to the community with the goal of helping them plan and adapt to the changes that are about to occur."

In their study, the researchers started by investigating the environmental impacts of the Muskrat Falls hydroelectric dam, located in Labrador, Canada. According to the researchers, in 2017 this dam will flood a large region upstream that is upstream from a fjord known as Lake Melville. Because communities in this area rely on the lake as a primary source of food, the researchers examined methylmercury levels of the lake.

"We found more methylmercury in the water than our modeling could explain," Amina Schartup, a postdoctoral fellow and the paper's first author, said in a statement. "All of the methylmercury from the rivers feeding into Lake Melville and from the sediment at the bottom of the lake couldn't account for the levels in the water. There was something else going on here."

The methylmercury concentration found in plankton in the lake peaked between one and 10 meters below the surface. This is similar to findings from the central Arctic Ocean. The link between these bodies of water can be explained by the eating habits of plankton.

According to the researchers, when fresh and salt water meet, the salinity increases in deeper waters. In this area, while plankton feed on settling debris, bacteria turns the mercury that is naturally present there into terribly poisonous and easily absorbed methylmercury, which accumulates and magnifies as it works its way up the food chain.

"This system is incredibly efficient at accumulating methylmercury," said Schartup, who explained that this same system could be applied to the Arctic, where freshwater from melting ice mixes with salt water.

Sunderland and her team collected soil cores from the inland areas that expected to be flooded for hydroelectric power in 2017. They then simulated flooding by covering the cores with river water, and within five days, methylmercury levels in the water over the cores increased 14 fold. From this the researchers estimated that increases of this toxin range from 25 to 200 percent.

"We removed the litter layer and surface vegetation prior to saturating the cores, which is known to decrease methylmercury levels, " Sunderland said in the release. "Without clearing that, the actual pulse of methlymercury to the Lake Melville ecosystem may be much greater."

Communities that rely on these types of ecosystems for food could be devastated by downstream effects of flooding for hydroelectric development.

"Scientists have a responsibility to understand and explain how environmental systems will react before they are modified," Schartup said in the release. "Because once the damage is done, you can't take it back."

Their findings were recently published in the journal Proceedings of the National Academy of Sciences.

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