Ice and associated algae in the central basin of Lake Erie in 2008

Ice atop lakes doesn't necessarily freeze the life down under

Life under the ice of freshwater lakes is more amazing — more alive — than anyone thought, according to new research. Limnologists — those who study lakes — have mostly thought that plants, animals and algae pretty much took winters off.

The winter picture is now clearer thanks to an international study by 62 scientists — including Aaron Galloway of the UO's Oregon Institute of Marine Biology. Their findings, which are detailed in an open-access paper published online Nov. 28 by the journal Ecology Letters, land as climate change is warming the world's lakes.

“As ice seasons are getting shorter around the world, we are losing ice without a deep understanding of what we are losing,” said the study's lead author Stephanie Hampton, director of the Center for Environmental Research, Education and Outreach at Washington State University. “Food for fish, the chemical processes that affect their oxygen, and greenhouse gas emissions will shift as ice recedes.”

Galloway was a postdoctoral researcher on the project and co-led the effort to compile the data before leaving Washington State to join the UO in 2015. The data synthesis led to an in-person and online meeting to analyze the data at the National Center for Ecological Analysis and Synthesis.

"This project represents a triumph in both natural history and a demonstration of three key attributes of the human spirit: curiosity, perseverance, and sharing," Galloway said. "Natural historical observations are the backbone of our understanding of the natural world. This project pulled together existing observations collected by literally hundreds of dedicated limnologists from all over the world, who put themselves out on lakes that were covered by ice."

Winter's lower temperatures and light levels may slow the activity of life under the ice, but algae and zooplankton are still abundant, said Liz Blood, program director in the National Science Foundation’s Division of Environmental Biology, which funded the research. "What will happen if lake ice cover decreases in warming temperatures? These results are a significant step in understanding what may be far-reaching changes for lake ecosystems.”

It turns out that what happens in winter, including photosynthesis, is important in the production of food sources for fish at the start of their growing season, the researchers found.

Marine biologists have documented the key role of sea-ice in supporting polar food webs. Understanding the under-ice ecology of both freshwater lakes and the oceans is now important in Galloway's research. As a marine biologist, he said, lakes are interesting because they range in size and age, as well as their connectivity to each other and other parts of the biosphere.

"I study how energy and essential dietary molecules from primary producers such as phytoplankton, seaweeds and sea grasses support aquatic food webs," he said. "Under sea ice, you see the growth of foods higher in beneficial fatty acids, which is important because these algae may account for as much as 30 percent of overall annual productivity.
 
"Depending on the ice conditions, phytoplankton can grow under ice and provide nutritional subsidies to the primary consumers during the winter and spring when the ice melts and the algae falls to the bottom," Galloway said. "It is thought that this production may be particularly rich in omega-3 polyunsaturated fatty acids. Changes to the duration or extent of ice cover in both lakes and the ocean may affect the availability of these important nutrients to zooplankton, fish and other predators."

For more complete details about the study, see the news release issued by Washington State University.

— By Jim Barlow, University Communications, and Eric Sorensen, Washington State University Communications