TOLEDO, Ohio —
Since the 2014 water crisis, technology to monitor Lake Erie's health has improved, but scientists can also use wildlife to check water conditions.
Although they can be annoying when they are all over your car, mayflies are a good thing for the lake.
"They need good amounts of oxygen, appropriate temperatures and can't handle too much chemical pollution in the lake," Brian Alford, assistant director of Stone Laboratory said. "For them to develop into the adults you see swarming around today, they have to have good water quality."
Mayfly larvae keep the bottom of the lake clean and aerated.
"They burrow into the lake and make little tubes," Alford said. "Then they more or less pump oxygenated water into that sediment, into those tubes, with their gills."
The bugs can also keep phosphorous that naturally occurs at the lake bottom from going into the water, but Alford said most of the phosphorous in the lake is from runoff.
Phosphorous is one cause of the toxic algal blooms.
From the 1950s through the 1990s, mayfly populations declined due to poor lake health.
"Especially prior to the Clean Water Act regulations where the lake was not providing enough water quality for the larvae of the mayflies so they almost disappeared," Alford said.
Since new regulations have been put in place and the lake has started to heal, swarms of the bugs are starting to reappear.
"Mayflies are super important to the food web of Lake Erie and any other aquatic system they're associated with," Alford said. "Their larvae provide food for fish. They also provide food for when they emerge to the adults you see today, they provide food for birds that are migrating up to Lake Erie."
Mayflies are an important part of walleye diets, which are another species scientists use as an indicator of lake health.
"Good water quality, the right warming rate, the right food for larvae to hatch and when we get all that, we usually see the benefit of that with high walleye populations," Travis Hartman, Lake Erie fisheries program administrator said.
Hartman said if there is a good population of hatchlings, it normally indicates good water conditions. He said as of right now, things look good as the Ohio Department of Natural Resources estimates there are over 72 million walleye in the lake.