DULUTH — The Duluth-based Natural Resources Research Institute has been awarded a $3 million grant from the U.S. Environmental Protection Agency to continue studying the bottom of the food chain in the Great Lakes — work that includes collecting water samples and boring into lake sediment to learn hundreds of years of history.

The EPA grant is part of the Great Lakes Restoration Initiative — work to restore and protect freshwater resources. It is funding that the institute has also received in the past.

Scientists are tracking changes to make predictions about the future, according to Euan Reavie, who leads the research team with ties to the University of Minnesota Duluth.

"We know the base of the food web in Lake Superior is changing quickly as a result of the fact that it is warming up faster than any large lake in the world — which is changing the physics of the system. So, not surprisingly, it's changing the biology as well," Reavie said. "And that's a concern."

The Great Lakes Biology Monitoring Program started more than 40 years ago to track the health of the Great Lakes. The Natural Resources Research Institute has been studying phytoplankton, microscopic algae at the bottom of the ecosystem on the Great Lakes, for the past 15 years. Scientists are looking for emerging threats — and ways to manage those threats.

Researchers have seen the collapse of deep-water food webs since the invasion of quagga mussels in Lake Michigan and Lake Huron. The zebra mussels' relatives filter water and remove plankton, according to the National Invasive Species Information Center. Lake Erie is again becoming eutrophic, in which high concentrations of nutrients in the water create toxic algae blooms, according to the EPA. It was a problem in the 1970s, and it's back again, Reavie said.

Leaders at the Superior, Wis.-based National Estuarine Research Reserve System also celebrated news of the grant. Their research on the St. Louis River often runs parallel — including monitoring changes in phytoplankton. The river feeds into Lake Superior.

"We're also working here and working with (Reavie) regularly to better understand water and the health of water in the estuary because it's such a huge contributor to the lake," said director Deanna Erickson. "You really do need data like we provide to understand the contemporary water conditions and what it means."

There are reasons to be optimistic, Reavie said.

"We're always going to be evaluating sustainability," he said. "Oftentimes that involves pushing back on industrial development. Often there needs to be tradeoffs. With human existence comes environmental damage, it seems. Can we minimize or eliminate that? Hopefully."