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The number of severe algal blooms in Lake Erie will likely double during the next century, according to new research from The Ohio State University.
Although fertilizers from farms played a major part in last year’s record-breaking algae bloom in Lake Erie, climate change is also a driver, reported Noel Aloysius of Ohio State and Hans Paerl of the University of North Carolina at Chapel Hill. The two researchers spoke at last month’s meeting of the American Geophysical Union in San Francisco.
Moreover, power plants help create conditions that are conducive for algal blooms, researchers say.
According to the federal Environmental Protection Agency, the electricity sector is responsible for more than 30 percent of the United States’ greenhouse gas emissions. Those emissions include carbon dioxide and a variety of other compounds that have been shown to contribute to climate change.
Ultimately, one of the most productive fisheries in North America is at risk. Lake Erie is the smallest of the Great Lakes, but it also supports a commercial fishing industry worth almost $2 billion per year. It’s arguably the walleye capital of the world, say researchers at the Ohio Sea Grant/Ohio State Extension.
A healthy freshwater lake environment includes a variety of algae and other organisms that provide food for other species in the food web. Normally, the system is in balance. Under certain conditions, however, huge amounts of nutrients enter the lake. That can happen, for example, when snow melt and heavy spring rains wash excess phosphorus and nitrogen fertilizer from farmlands into streams and rivers that drain into Lake Erie.
Just as the nutrients feed crop growth on farmland, they also help certain bacteria known as blue-green algae grow. And during a hot summer, those blue-green algae can grow out of control. That produces a bloom, which upsets the normal balance and can lead to a bright green slime in the water.
The algal bloom’s slime isn’t just ugly. It can also be poisonous. Those blue-green algae include microcystis, and some forms of it produce a toxin that is harmful to fish and other species exposed to it.
Toxins from an algal bloom were responsible for the shutdown of Toledo’s water works in August 2014, leaving hundreds of thousands of people without safe drinking water. The 2015 algal bloom in Lake Erie covered an even bigger area, although it did not have the same toxicity problems that the earlier bloom did.
“There are different forms of microcystis, and some of them are not capable of producing the toxin,” explained Jeffrey Reutter, former head of Ohio State’s Stone Laboratory, speaking at a panel at the Society of Environmental Journalists’ annual meeting in Norman, Okla. last fall.
Harmful blooms also interfere with the ecosystem of the lake. In particular, the blue-green algae crowd out beneficial types of algae that various species rely on for food.
‘We need to consider climate change’
Reductions in nutrients from runoff are needed to deal with the problem of harmful algal blooms, Aloysius and Paerl said. But they also stressed the role of climate change in causing more and worse blooms.
“A key driver in Lake Erie is the Maumee [River] and the changing pattern of precipitation,” Aloysius noted. More severe storms linked to climate change could wash even larger amounts of nutrients into the Great Lakes.
In fact, most types of extreme weather linked to climate change will favor the increased frequency of harmful blooms, Paerl said. For example, extreme heat may harm other species, but blue-green algae have survived even hotter periods in Earth’s history. So instead of being stressed, he said, “They’ll like it even more.”
“We need to consider climate change as a factor when planning future nutrient runoff pollution programs,” Paerl said.
The power plant connection
Aside from their link to climate change, greenhouse gas emissions from fossil fuel plants also include nitrogen oxides, which can add to nitrogen already entering the lakes as runoff from farming and other sources.
Power plants could also contribute to algal bloom problems as they use large quantities of lake water for cooling and then release it back into the lake. “Thermal discharges from power plants tend to create conditions that are conductive to harmful algal blooms, because they like warm water,” Reutter said.
Additionally, harmful algal blooms increase the risk that toxins from decades-old power plant pollution in lake sediments will go back into the water. Those pollutants can include mercury, arsenic, cadmium and other chemicals.
As algal blooms die off, they expand the lake’s “dead zone” — an area where dissolved oxygen levels are too low for fish to live. “When it goes from an oxidizing environment with oxygen present to a reducing environment with no oxygen present, the heavy metals that are buried within the sediment redissolve into the water,” Reutter explained.
“So when we get a dead zone, you’re going to have high concentrations of a number of heavy metals,” which can cause more problems, Reutter said.
Among other things, the redissolved metals could harm fish and other aquatic species. If levels got too high, the water might even fail to meet standards under the Safe Drinking Water Act and be deemed unsafe for people to drink.
“We need to look forward,” Frank Szollisi, of the National Wildlife Federation, said at the Society of Environmental Journalists meeting. “We need to understand the implications that climate change is having on the land and on the water.”
Otherwise, he said, the consequences for Lake Erie’s fishery could be dire: “We could lose the walleye. We could lose the yellow perch.”
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