GUELPH, Ontario — Researchers here have found that more frequent “extreme winds events” may be whipping up trouble for Lake Erie’s water quality and what was found in the study could have the potential to play out in other Great Lakes, such as Ontario.
The new study released by the University of Guelph says those more frequent wind events are drawing up deep water containing low oxygen and high phosphorus that may harm drinking water and fish in western Lake Erie.
The researchers’ paper was published in Nature Scientific Reports. It shows increase in wave power between 1980 and 2018 during August in the Great Lakes. These changes were associated with increasing significant wave heights likely to have several effects, including higher sediment resuspension.
“I’ve been working on this subject for a while, but it was more recently that we found that this strange movement of water from the central basin of Lake Erie was actually moving into the lake’s western basin, opposite to the regular flow of the lake,” Josef Ackerman, professor in the department of integrative biology said in a phone interview.
Mr. Ackerman said that a U.S. study found that wave power in the ocean was a good measure of the amount of energy coming from the atmosphere into the ocean.
“We tried to use that to figure out if it would help us understand that flow of water in the reverse direction,” he said.
Researchers especially wondered about “upwelling”: A process in which deeper, cold water rises toward the surface — the displaced surface water is replaced by cold, nutrient-rich water that “wells up.”
The researchers used wind power as a “proxy,” Mr. Ackerman said, as an indicator of when the upwelling could occur. They relied on scientific equipment on buoys dotted throughout the five Great Lakes to get wind power data.
“We’re looking at what we would call more extreme winds,” Mr. Ackerman said. “If you lined up all the winds, they would be like the top 20 percent of the wind speeds in that time.”
Researchers were especially interested in the increased winds from the south and southwest, which related to “significant” increase in wave power.
“That direction is the predominant direction, but it’s also the direction causing the upwelling in Lake Erie that most of the paper is about,” Mr. Ackerman said.
In shallow lakes and parts of freshwater bodies such as the western end of Lake Erie, winds normally keep water evenly mixed, providing consistent amounts of oxygen and nutrients. Lake Erie is the shallowest of the Great Lakes.
The findings in the study conclude that extreme wind events have increased from one every other year to three a year from 1980 to 2018.
The currents caused by the winds tilt the temperature gradient (thermocline) and pull up water with low oxygen (hypoxia) and lots of phosphorus. In Lake Erie, that water from the deep central basin flows paradoxically into the shallower western basin, opposite the normal flow direction.
“We also found higher wave power in August in Lake Ontario, so winds and water currents should be responding to this as well,” Mr. Ackerman said.
He said this likely will lead to more episodes of upwelling on the north shore of Lake Ontario.
“I do not know the extent and magnitude of the upwelling, but it may be a concern locally in Lake Ontario. There are other locations in the Great Lakes with multiple basins, where upwelling may lead to the introduction of hypoxic water from one basin to another similar to what we found in Lake Erie.”
He noted the shallow basin in Lake Erie is the western basin, which does not stratify for long periods compared to the other basins and Lake Ontario, which all stratify seasonally.
Mr. Ackerman said that Lake Ontario is nearly at the same orientation of Lake Erie: Ontario’s western part is toward the southwest and northern part is toward the northeast. “The similarity in orientation of lakes Ontario and Erie means that the direction of the winds and their effects on the water currents and waves should be similar,” he said. “That’s why I expect the frequency in upwelling in Lake Ontario to have increased.”
important for fish studies
Marc Gaden, spokesman for the Michigan-based Great Lakes Fishery Commission, said the new study is important because it connects climate change to what can happen on the Great Lakes.
“There’s an expectation for a net increase in precipitation in the Great Lakes region,” Mr. Gaden said in a phone interview. “Most models show more frequent and more extreme events, like storm events. What this study says is that more stronger wind events mean the phosphorus and low oxygen water at the deeper depths is likely to get whipped up. It’s one thing to have breezes out there, but the more intense wind events and storms that the models show raise a lot of questions about what happens when the lakes, especially a lake like Erie, mixes like that.”
Mr. Gaden said that low oxygen dead zones normally stay at the bottom of the water column.
“It puts fish at less of a risk of coming into contact with that and harming the fishery,” Mr. Gaden said. “What Ackerman and all have done is connect a couple of things — climate change and what happens when that churning occurs. It’s another piece of the puzzle. It helps us better understand the long-term changes in the ecosystems that is expected to occur because of the changing climate.” The water with low dissolved oxygen being shifted around, Mr. Gaden said, isn’t good for fish.
“It has an effective course on reducing the oxygen that fish need in their water to thrive and survive,” he said. “It reduces the amount of habitat available for fish if they have to leave the area because it’s not habitable as a result of low oxygen.”
He added, “Beyond that, it affects the fish demographics; cold water fish, warm water fish, where they go. These are bottom-up forces that become more and more important in the Great Lakes ecosystm.”
More phosphorus can cause harmful algae blooms, reducing water quality and making it more difficulty for fish to survive. “One of the problems with phosphorus is that it can sit on the sediment on the bottom of the lake and it can get remobilized, or come back into the water column,” Mr. Ackerman said.
The increased frequency of interbasin upwelling in the new study was confirmed using historical records of lake bottom water temperature, as well as dissolved oxygen and total phosphorus concentrations. “This is the first time that wave power has been identified as an indicator of climate change-driven biogeochemical responses in lakes,” the report reads.
According to NOAA, algae blooms become harmful to the ecosystem when the “blooming organisms” contain toxins, noxious chemicals or pathogens. Those can lead to death of nearby fish and produce harmful conditions to marine and human life. Runoff from fertilizer nutrients have been linked to increased algae blooms.
“If you were trying to figure out what was going on, you could say all the stuff we’ve been doing for phosphorus control isn’t working, but now you realize that there’s another reason that phosphorus could be coming into the system that’s not related to the traditional inputs from the rivers,” Mr. Ackerman said. “It’s from the central basin.”
He added, “The one way to control this would be to minimize the amount of phosphorus everywhere. That way, there would be less coming in. That would be the ultimate goal.”
In November, the U.S.-based Interagency Working Group on Harmful Algal Bloom and Hypoxia Research and Control Act released a report to Congress that provided a summary of federal agency efforts to address HABs and hypoxia in the Great Lakes region. The report was updated from one in 2017.
The report notes that since 2017, “federal agencies in the IWG-HABHRCA have made progress in addressing the causes of harmful algae blooms and hypoxia in the Great Lakes, which, in turn, has helped limit their impacts.”
Achievements since the 2017 progress report include: advances in detecting and forecasting harmful algal blooms and their toxins; new models showing when HABs threaten drinking water intakes; publications documenting the transport of nutrients into the Great Lakes and watershed conservation practices that limit their concentrations; and improved coordination with stakeholders through citizen science.
A study released earlier this year by the University of Minnesota at Duluth says that benthic (bottom) invaders control the phosphorus cycle in the Great Lakes. “The invasion of the Laurentian Great Lakes, the world’s largest freshwater ecosystem, by dreissenid (zebra and quagga) mussels has dramatically altered the ecology of these lakes,” the report says.
Researchers wondered how dreissenids affect the cycling of phosphorus, the nutrient that limits productivity in the Great Lakes.
“We show that a single species, the quagga mussel, is now the primary regulator of phosphorus cycling in the lower four Great Lakes,” the report states. “Our results show that a single invasive species can have dramatic consequences for geochemical cycles even in the world’s largest aquatic ecosystems. The ongoing spread of dreissenids across a multitude of lakes in North America and Europe is likely to affect carbon and nutrient cycling in these systems for many decades, with important implications for water quality management.”
“We’ve learned more and more what these things are doing to the Great Lakes ecosystem” Mr. Gaden said. “They’ve changed everything. This (University of Guelph) study is important because it gives us more information about how climate change affects the region in the fisheries and how increases in phosphorous could lead to lower water quality.”
Mr. Gaden said the phosphorous is often mistakenly labeled as a pollutant, but it’s an essential nutritent for life, therefore correct management of it in the Great Lakes is important.
“What Lake Erie has is too much of a good thing,” he said.
Ackerman said the new study might help resource managers in both Canada and the U.S. to connect upwelling — and the underlying “wind-wave tandem driven by climate change” — to changes in fish stocks in spot surveys.
“We didn’t invent anything,” Mr. Ackerman said of wind events/water quality study. “We basically figured something out because we were interested in what was going on and it seemed one thing led to another, a kind of snowball effect.”
Mr. Ackerman conducted the wind events/water quality study with Aidin Jabbari and co-authors Leon Boegman, a professor of civil engineering at Queen’s University, and Yingming Zhao with the Ontario Ministry of Natural Resources and Forestry. The ministry monitors fish stocks for joint Canadian management with the United States through the Great Lakes Fishery Commission.
Mr. Ackerman received his master’s degree at SUNY Stony Brook, where he examined the hydrodynamics of eelgrass canopies. He then studied at Cornell University, Ithaca where he researched the biomechanics of submarine pollination in eelgrass for his Ph. D. That was followed by a postdoctoral/research associate stint in mechanical engineering at the University of Toronto and the Royal Ontario Museum where he examined the biomechanics of zebra mussels.