On the Great Lakes, scientists are making a ‘Winter Grab’ of rare data | Science

GREEN BAY, WISCONSIN—On a brutally cold day here earlier this week, Kirill Shchapov stood 200 meters off the shore of Lake Michigan, using a green auger to drill into a glistening ice sheet that stretched to the horizon. A fountain of water erupted when he yanked the auger from the hole. But soon Shchapov, a limnologist at the University of Minnesota (UM), Duluth, and other researchers were busily lowering nets and instruments through the opening, collecting water samples and shellfish that lived on the lake floor some 5 meters down.

The frigid fieldwork is just one element of an ambitious U.S. and Canadian research effort—dubbed the Winter Grab—aimed at better understanding how the five Great Lakes function in the dead of winter, and how climate change is reshuffling their ecosystems. On 14 February, as part of a weeklong campaign timed to coincide with the season’s heaviest ice cover, dozens of researchers from 19 research institutions and government agencies used sleds, snowmobiles, and even airboats and icebreakers to fan out to about 30 sites to study the lakes’ life and chemistry.

Scientists have long conducted such studies during the warmer months, but “the Great Lakes and large lakes in general have an especially acute sort of winter knowledge gap,” says UM limnologist Ted Ozersky, who led the Winter Grab. Trying to understand lakes using just warm weather studies, Shchapov adds, is akin to reading just half a book: “How does the story develop?”

Ozersky hatched the idea for the Winter Grab after a 2019 lake science workshop that highlighted the dearth of cold-weather data: Fewer than 5% of Great Lakes studies, for example, have been done in winter. One reason for the seasonal bias, researchers say, is that lakes were often considered relatively dormant and uninteresting in winter. In addition, academic researchers typically sample in the spring and summer, when the water is safer and more accessible, and classes aren’t in session. As a result, scientists know relatively little about how lake organisms graze, compete, and hunt during winter, or how nutrient cycles vary by season.

Now, climate change is threatening those cold-season ecosystems. A study published last year in Nature Geoscience, for example, found that for every 1°C increase in global air temperature, lakes lose almost 10 days of ice cover. And an analysis published in Geophysical Research Letters in 2015 showed that, of 235 lakes around the world, the Great Lakes are among those warming the fastest. Lake Superior is now ice-free for about 2 months longer each winter than it was in the late 1850s. And some scientists predict the Great Lakes will be ice-free by the end of the century.

“We are losing ice without a really clear understanding of what we’re losing in terms of the ecology under that ice,” says Stephanie Hampton, a freshwater scientist at Washington State University, Pullman, who is not involved in the Winter Grab. The undersides of ice sheets can provide habitat for plankton and microbes, for example, and the extent and thickness of ice cover can alter the amount of light penetrating the water, affecting chemical and biological processes.

Off the coast of Green Bay this week, scientists collected jugs of water in a bid to catalog the microorganisms that are active under the ice and examine how they might affect nutrient cycles. The samples are going to biogeochemist Maureen Coleman’s lab at the University of Chicago, which will use DNA sequencing and other methods to identify microbes and other organisms. The data will complement a similar, 5-year-long data record that Coleman’s lab has already compiled from samples taken in the warmer months.

“Maybe there’s some new species that are specialists that come up in the winter—we really just have no idea,” Coleman says. She calls the Winter Grab—which will end early next week—“unprecedented” and “exciting, because we’re getting a snapshot across this wide geographic area all in the same week.”

Other researchers are examining winter algae populations, which might help predict the likelihood of algal blooms in summer. One thing is clear, Shchapov said as he prepared to dunk a device that measured oxygen levels into the hole: A lake in winter “is not dead at all.”

Ultimately, Winter Grab researchers hope their findings will spur efforts to study winter lakes on an even larger scale, using icebreakers, floating buoys, and instruments moored beneath the ice. “There’s been this groundswell of research happening in winter,” Hampton says, “because we get more and more excited as we talk to each other and recognize that [lakes are] ecologically a lot more active than we thought.”