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WQAD.com

Dramatic drop in mayflies linked to Mississippi River pollution, warming climate

The mayfly may be the "canary in the coal mine" when it comes to the environment of the Upper Mississippi River.
Credit: wqad

The mayfly may be the "canary in the coal mine" when it comes to the environment of the Upper Mississippi River. 

Every year, residents all along the Upper Mississippi River gear up for the yearly hatching of mayflies. In some locales, they are called "Canadian Soldiers" or "shadflies." In fact, the Mississippi River town of Savanna, Illinois has a "Shadfly Fest" every July, embracing the little critter.

Mayflies spend most of their lives in a larval stage underwater, eating up algae in the shallows of the river. "Hatching" doesn't actually have anything to do with the month of May. In fact, most appear in June and July. 

Hatchings aren't just a small occurrence. Researchers from the University of Notre Dame, University of Oklahoma, and Virginia Tech estimate the population of the average hatching to be around 88 billion bugs. They tracked the hatchings using Doppler radar over a period of eight years from 2012-2019. Their findings are bringing us more questions than answers, however.

In just seven years, they have discovered a remarkable 50% drop in the population of mayflies. The research study included the Upper Mississippi River basin and the western Lake Erie region. 

The researchers began the study with a goal to find out how many mayflies take flight each year. Little did they know, they'd come upon a conclusion that has led some to call the mayfly the "canary in the coal mine."

The results are published in the journal Proceedings of the National Academy of Sciences.

Phillip Stpanian is one of the scientists in the study, telling the National Science Foundation, that the mayflies provide 12 trillion calories into the food web.  "We can assume these insects have a nearly instant impact on the birds that survive on them when they descend on their respective shorelines."

Dan Gruner is a program director of the Division of Environmental Biology for the National Science Foundation: "This study gives us new ways to understand population trends of insects, which form the base of the food web upon which we all depend."

Initial studies suggest that mayflies are impacted by a decreasing water quality. Increased nutrient and sediment runoff from agriculture could be to blame. Also, warmer temperatures may be impacting their survival. As the climate warms in the late-Spring and early-Summer, the window of optimal conditions may be shrinking. 

Certainly, the findings are showing how tightly land-use and water are linked. It's not yet known how the abrupt drop in mayfly population will affect the animals that depend on them for survival. Those include fish, frogs, newts, and birds.

-Meteorologist Eric Sorensen