Mayfly declines in North American waterways

Researchers report recent declines in mayfly emergence over major North American waterways. Seasonal animal movements drive the transport of biomass and nutrients between ecosystems, thereby influencing community structure and ecosystem function. However, quantifying such movements at ecosystem scales remains technically challenging. Phillip Stepanian and colleagues used data from weather surveillance radar to monitor an extreme example of such movements: the annual emergence of mayfly swarms from aquatic to terrestrial habitats in North America. The authors surveyed mayfly abundance over the Western Lake Erie Basin and the Upper Mississippi River from spring 2012 to the present. Up to 87.9 billion mayflies were observed emerging during a single event, releasing more than 3,000 tons of biomass into the airspace in a matter of hours. In recent years, however, abundances in both waterways has declined dramatically: 84% in Lake Erie from 2015 to 2019, and 52% in the Upper Mississippi from 2012 to 2019. The declines may reflect deteriorations in water quality due to a combination of factors, including warming water, nutrient-rich runoff, and pesticides. Such factors could ultimately lead to the extirpation of mayflies from these waterways, with consequences for the insectivores that prey on mayflies, according to the authors.

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Article #19-13598: “Declines in an abundant aquatic insect, the burrowing mayfly, across major North American waterways,” by Phillip M. Stepanian et al.

MEDIA CONTACT: Phillip M. Stepanian, University of Notre Dame, South Bend, IN; tel: 574-631-2566, 412-852-0281; e-mail: <

[email protected]

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