Aquatic Sciences Meeting, Albuquerque 2001

SS40 Long-Term Research Programs in the Twenty-first Century (Spatial and Temporal Connections)

Date: Thursday, February 15, 2001, Time: 12:00:00 PM

Location: Ruidoso/Pecos

Schloesser, D, W, USGS, Great Lakes Science Center, Ann Arbor, USA,

Bur, M, , USGS, Great Lakes Science Center, Sandusky, USA,

Ciborowski, J, , University of Windsor, Windsor, Canada,

Corkum, L, , University of Windsor, Windsor, Canada,

Krieger, K, , Heidelberg College, Tiffin, USA,

DENSITIES OF BURROWING MAYFLIES IN WESTERN LAKE ERIE OF THE LAURENTIAN GREAT LAKES: 1930S TO 1990S

Burrowing mayfly nymphs were abundant in many areas of the Laurentian Great Lakes prior to 1950s. In the 1950s, low dissolved oxygen extirpated many of these populations. In western Lake Erie, few nymphs were found between the early 1960s and late 1980s (0-23% of sites and 0-7 nymphs/m2). Recovery of nymphs began between 1991 when nymphs were found at 12-38% of sites and 1993 when nymphs occurred at 44-55% of sites. By 1997, nymphs were present at 88% of sites and densities of nymphs increase from <10/m2 in 1991 to 10/m2 in 1993, 37/m2 in 1995, and to 392/m2 in 1997. Prior to the mid 1950s, densities of nymphs were greater in offshore than nearshore waters, but in the 1990s greater densities occurred in nearshore than offshore waters suggesting the recovery may not yet be complete. The sudden increase in burrowing mayfly nymphs in western Lake Erie in the 1990s is attributed to soil-runoff and pollution-abatement programs initiated in the mid 1960s, and possibly to changes caused by the exotic zebra mussel, Dreissena polymorpha.

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Aquatic Sciences Meeting, Albuquerque 2001

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