Mayflies Reveal Differences in Bottom Conditions in Lake Erie
Ann Arbor, MI — Mud-dwelling mayflies on the bottom of Lake Erie are revealing differences in water and sediment quality in different parts of the lake, according to researchers. The insects, known to biologists as Hexagenia, require oxygen dissolved in the water year-around in order to survive and multiply.
The mayflies - native to Lake Erie - have been plentiful in mud of the western basin from Sandusky, Ohio, and Leamington, Ontario, west to Toledo since the 1990s as a result of improving lake quality. Their return to the western end of the lake led biologists from Heidelberg College in Ohio, the U.S. Geological Survey, and the universities of Windsor and Waterloo in Ontario to predict that the mayflies would also become more widespread and abundant further to the east in areas of the lake near Cleveland; Erie, Pennsylvania; and Buffalo, New York. To find out, they looked for mayfly larvae in bottom mud from much of Lake Erie from 1997 through 2005.
In studies funded by the USEPA, Environment Canada, the Sea Grant Program, and the Ohio Lake Erie Protection Fund, the researchers found that the larvae have not successfully colonized mud of the central and eastern basins. "We predicted that the mayflies would spread eastward from the western end of the lake and begin to occupy suitable mud in the other parts of the lake," said Dr. Ken Krieger of Heidelberg College, one of the lead researchers on the project. "Instead, after increasing in numbers in some areas off the Ohio shore through 2000, they virtually disappeared in 2001 and have not returned," he said.
The scientists are not sure why the mayflies, also known to locals by such names as junebugs, Canadian soldiers (on the American side!), and shadflies, are restricted to the western end of the lake. Long-time residents along the lake shore recall large summer swarms of the adult insects during the first half of the last century from Toledo to Cleveland, Ohio, and Buffalo, New York.
The scientists point to evidence that cold temperatures in the central and eastern basins (over 75% of the lake) may naturally prevent the mud-dwelling larvae from successfully completing their life cycle. The loss of oxygen in summer from a large area of the lake bottom north of Lorain and Cleveland, Ohio - known as the "dead zone" because animals can't survive there in the absence of oxygen - also appears to play a role in keeping the mayflies away.
Original Publication Information
Results of this study "Distribution and Abundance of Burrowing Mayflies (Hexagenia spp.) in Lake Erie, 1997–2005," are reported by Kenneth A. Krieger, Michael T. Bur, Jan J. H. Ciborowski, David R. Barton and Don W. Schloesser in the latest issue (Volume 33, No. sup1, pp. 20-33) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2007.
Contacts
For more information about the study, contact Ken Krieger, National Center for Water Quality Research, Heidelberg College, 310 E. Market St., Tiffin, OH 44883, kkrieger@heidelberg.edu, (419) 448-2226.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
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