Water sampling on Lake Erie in the summer is pretty simple: check for decent weather, find a boat, cruise to the sampling locations, take samples, bring them home.
In winter, things get a bit more complicated: winter storms on Lake Erie can be frequent, so even if the lake isn’t frozen, chances for sampling trips are likely limited. A frozen lake means needing to recruit an ice breaker to get to sampling locations, and sometimes, even those winter-ready ships aren’t quite able to travel as freely as a research project may require.
This was the case for Dr. R. Michael McKay at Bowling Green State University during the winter of 2015. As part of ongoing research into winter algae populations in Lake Erie, McKay, his colleague Dr. George Bullerjahn and collaborators from Environment Canada have been collecting samples for analysis since 2007.
“In the past, we’ve been able to partner with both Canadian and U.S. Coast Guards and their ice breaking programs,” McKay explained. “That cooperation has been very fruitful and allowed us to obtain samples during this time of year where it’s quite difficult to get out to sample. However, given the ice thickness, there was limited Coast Guard activity on Lake Erie last winter.”
During the heavy ice presence on Lake Erie in the winter of 2014, Environment Canada staff were able to charter a helicopter and still collect samples despite not being able to work from a Coast Guard ship. However, the agency’s budget did not allow for the same process in 2015, so McKay contacted Ohio Sea Grant to see whether funding could be made available on the U.S. side of the lake.
The researchers were able to obtain funding through Ohio Sea Grant’s Small Grants Program, which is open to applications year-round, to hire a helicopter service out of Lambertville, Mich. for a day of sampling on the Lake Erie ice.
“Because the helicopter operator was a little bit unsure about the safety of landing on the ice, he dropped down to let us off, and then he pulled back up and went back to Burke Lakefront Airport in Cleveland,” McKay said, explaining the safety measures the researchers took while being out on the ice. “We also had two-way radio and cell phone communication at some locations on the lake, and so we were able to maintain contact with him to have him come back to pick us up. And had there been a problem, he would have been able to get up there in just a few minutes as well.”
Winter algae populations in Lake Erie consist mostly of diatoms, tiny brown algae surrounded by silicate shells. Like other plants, diatoms need sunlight to survive and grow, so they tend to attach to the underside of lake ice once it forms on the water surface. This means varying ice conditions over the years could have a big influence on summer food webs, which in part depend on these winter diatoms, making it important to understand how the diatoms contribute to other organisms’ life cycles.
McKay and post-doctoral researcher Mark Rozmarynowycz used a handheld auger – similar to ones used by ice anglers – to drill through the lake ice, keeping the ice core intact for later analysis in the lab. They then collected environmental data like water temperature and dissolved oxygen, as well as light penetration through the ice and into the water column.
“By the time we reached about 3 meters in depth, the light was diminished 100-fold from the surface,” McKay said. “It didn’t pass any further than that into the water column.”
Light penetration is an important factor in winter algal growth because algae rely on sunlight for photosynthesis, without which the diatoms would essentially starve to death. “One thing we did find with the winter of 2012, which had almost no ice, was that there was a major disruption in the phytoplankton community,” McKay said.
That may seem counterintuitive since phytoplankton is exposed to more light without ice on the surface of the lake and should therefore thrive. However, without ice, there is no barrier to prevent wind from mixing the diatoms throughout the water column, which keeps a lot of the phytoplankton quite literally in the dark.
That light limitation could become an increasing concern as more and more winters in the Great Lakes are defined as low-ice winters. With lower phytoplankton production come lower numbers of zooplankton, which in turn are an important food source for fish like Walleye and Yellow Perch that fuel Ohio’s multi-million-dollar sport fishing industry.
“We think these winter diatom communities are really important for the integrity of the fisheries in the lake because they serve as important food sources for zooplankton,” McKay explained. “And so when there is a disruption in this winter diatom community, the zooplankton are going to suffer and hence most likely the fish will suffer as well.”