Mayflies swarm across Toledo, signaling to a healthy Lake Erie ecosystem

While mayflies may be an annoyance for some, scientists say their emergence is actually a positive sign.

OREGON, Ohio — They may cover cars, buildings and sidewalks every summer, but experts say the swarms of mayflies appearing around Toledo are actually something to celebrate.

Dr. Christine Mayer, a professor at the University of Toledo, said the insects are a strong indicator of a healthy Lake Erie.

“They’re a little bit picky,” Mayer said. “They don’t want to just live anywhere. So if they’re abundant, that means that the water is sufficiently clean and has enough oxygen for them to survive underwater.”

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Although adult mayflies only live for a short time, they spend most of their lives underwater. Their brief adult lifespan is devoted to mating, to secure the next generation.

Mayer said despite the large swarms seen around, this year’s mayfly population is considered typical.

“Some years they’ll be more in Point Place than out by the islands, Put-in-Bay, and sometimes it’ll be the opposite, just depending on when they hatch and which direction the wind moves them,” she said.

Peak mayfly season, which Mayer says is now, coincides with the release of Lake Erie’s harmful algal bloom forecast. This year’s forecast calls for a moderate bloom, with above-average rainfall expected to carry more nutrients into the lake.

Mayer said while a severe algal bloom can negatively affect mayflies, any impact would likely be seen in next year’s population rather than this summer’s.

“If it becomes extreme, it could hurt mayflies,” Mayer said. “A bad algal bloom this year would impact the mayflies that come out next year.”

Mayflies are also an important food source for fish and other wildlife, making them a critical part of Lake Erie’s ecosystem.

Why some may think these are a summer nuisance, Mayer stresses the importance they have in our ecosystem. 

“Hopefully people can look at them and go, ‘Oh, I don’t like them, but I know they’re good,’” Mayer said. “Just sweep them up and put them in your compost or dig them into your garden. Turn the lights off and just appreciate them. Be proud of our mayflies.”