A proposed hydroelectric dam intended to provide “clean” energy in Labrador, Canada may have a more damaging impact on the environment than global warming, owing to a predicted increase in production of the potent neurotoxin methylmercury, according to a new study by researchers from UConn and Harvard University.

The amount of methylmercury is especially high in Arctic marine life but until recently, scientists haven’t been able to explain why. Now, research from the University of Connecticut and Harvard University suggests that high levels of methylmercury in Arctic life are a byproduct of global warming and the melting of sea ice in Arctic and sub-Arctic regions.

To mitigate global warming, many governments are turning to hydroelectric power. But the research also suggests that methylmercury concentrations from flooding for hydroelectric development will be far greater than those expected from climate change.

The research, published in PNAS, began as a review of the environmental impact assessment for the Muskrat Falls hydroelectric dam in Labrador, Canada. In 2017, the dam will flood a large region upstream from an estuarine fjord called Lake Melville.

The communities along the shores of Lake Melville are predominantly Indigenous and rely on the lake as a primary source of food. One of these communities – and two-thirds of Lake Melville – is part of Nunatsiavut, the first autonomous region in Canada governed by Inuit. When the impact report predicted no adverse downstream effects on Lake Melville, the Nunatsiavut Government reached out to researchers at Harvard for help.

Four years later, that initial review has morphed into a multi-pronged investigation that has led to important scientific discoveries about how methylmercury accumulates in the ecosystem and how it will affect communities that rely on the ecosystem for food and resources.

“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,” says Elsie Sunderland of Harvard’s John A. Paulson School of Engineering and Applied Science, who was joined in the research by Robert Mason, a professor of marine sciences at UConn. “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.”

What’s Happening

Sunderland and Mason examined baseline methylmercury levels in Happy Valley Goose Bay along the western shores of Lake Melville in 2012.

The research team, which included UConn Ph.D. student Kati Gosnell and research assistant Prentiss Balcom, noted that the concentration of methylmercury in Lake Melville’s biota – the plankton – peaked between 1 and 10 meters below the surface.

These findings closely matched findings from the central Arctic Ocean. The question was, why was there such a high concentration of methylmercury in biota in both systems?

The answer lay in the eating habits of plankton.

When fresh and salt water meet – in estuaries or when sea ice melts in the ocean – salinity increases as water deepens. This stratification allows fluffy organic matter that typically sinks to the bottom to reach a neutral buoyancy – meaning it can’t float up or down in the water column. This layer, called marine snow, collects other small settling debris and concentrates it into a feeding zone for marine plankton. The bacteria stuck in this zone are performing a complex chemical process that turns naturally occurring mercury into deadly and readily accumulated methylmercury.

“The methylation of mercury within the water column is an exciting finding, as until now most researchers have thought that methylation in sediments was the primary source for the methylmercury accumulating in coastal ecosystems,” says Mason. “The findings in Lake Melville also support our separate studies that have demonstrated methylation within laboratory-generated marine snow.”

The primary species of zooplankton in the Arctic and sub-Arctic are not picky eaters. Attracted to this layer of marine snow, the zooplankton go on a feeding frenzy that can last several weeks. During this time, methylmercury produced by the bacteria accumulates in biota and magnifies as it works its way up the food chain.

This same system can be extrapolated to the Arctic, where freshwater from melting ice is mixing with salt water, according to Amina Schartup, a Ph.D. graduate of the UConn marine sciences program who is now a postdoctoral fellow at Harvard.

If this system is already a pro at magnifying methylmercury, what happens when methylmercury levels increase due to reservoir flooding upstream?

The research team collected soil cores from the inland areas that are slated to be flooded for hydroelectric power in 2017. The team simulated flooding by covering the cores with river water. Within five days, methylmercury levels in the water covering the cores increased 14-fold. Extrapolating from this simulation, increases in methylmercury inputs from the Churchill River resulting from this pulse of methylmercury are estimated to be between 25 to 200 percent.

‘Our beautiful land’

What does that mean for the Inuit who rely on the lake for food?

“It would be devastating,” says David Wolfrey, a conservation officer from Rigolet, a Nunatsiavut community of about 300 people on the far eastern edge of Lake Melville.

The community has already been affected by climate change. There used to be snow and ice through May. Now, most of the snow is gone by April.

Wolfrey gets most of his food from the lake, fishing for salmon, trout, and rock cod, and hunting seals. And he is not alone. Nunatsiavut means ‘our beautiful land’ – the land and its resources are an integral part of Inuit life, culture, and economy. ‘Country food’ is one of the few affordable foods in the remote community, where subsidized eggs cost as much as $5 a dozen, milk costs $20 a gallon, and a frozen turkey costs $50. Contamination from increased methylmercury in the lake would compromise an important source of affordable food.

The Nunatsiavut Government is lobbying Nalcor Energy, the provincial energy corporation behind the development, and the Provincial and Canadian governments, to mitigate the downstream effects of the hydroelectric plant.

“Any kind of contamination is going to disrupt how we live as Inuit and impact our health and lifestyle,” says Sarah Leo, president of the Nunatsiavut government. “We need more research to understand the downstream effects, and we need to develop strategies to mitigate those effects. How can we cut down on contamination? How are we, as a community, going to adjust our lifestyle if we can no longer live off the land? These are all questions we need answered before flooding.”

Adds Schartup, “Scientists have a responsibility to understand and explain how environmental systems will react before they are modified. Because once the damage is done, you can’t take it back.”

This research was supported by the Nunatsiavut Government, The National Science Foundation, ArcticNet Inc., and Tides Canada Oak Arctic 765 Marine Fund Program.