Ecological Impacts Described

From July 28, 1992 (update #14)

A recent issue of "Mussel Morsels," an Ontario Ministry of Natural Resources newsletter devoted to the zebra mussel problem, included several short summaries of ecological topics presented at last February's Zebra Mussel Research Conference in Toronto, including:

* Every one of the native unionid clams sampled in Lake St. Clair by University of Guelph researchers P.L. Gillis and G. L. Mackie were encrusted with zebra mussels. A major decline in native clams has been observed since the arrival of zebra mussels.

* Walleye recruitment in Lake Erie in 1987, 1988 and 1989 (prior to the zebra mussel invasion) was poor, while average to good recruitment has occurred in 1990 and 1991, according to Steve Nepszy of the Ontario Ministry of the Environment. Other Canadian biologists report continued spawning of walleye and white bass on mussel-infested shoals.

* The zebra mussel invasion has led to increased water clarity, increased macrophyte and macroalgae growth, and changes in the composition of the Lake St. Clair benthic fauna, according to Ron Griffith of the Ontario Ministry of Natural Resources (OMNR).

* Mean numbers of planktonic larval mussels leveled off in the Western Basin of Lake Erie in 1991, and declined sharply in the West-central Basin in 1991, according to OMNR researcher Joe Leach. Mean annual chlorophyll-a concentrations in western Lake Erie now range from 1 to 2 micrograms per liter, which is indicative of oligotrophic conditions.

"Mussel Morsels" is published by the OMNR Zebra Mussel Coordination Office, P.O. Box 5000, Maple, Ont., L6A 1S9, Canada.

ID: 19920728-12.

The Zebra Mussel Update was a 4- to 8-page quarterly national newsletter published by the University of Wisconsin Sea Grant Institute from May 1990 through May 1997. The ZMU documented the spread of the zebra mussel -- an exotic nuisance mussel -- through North America's freshwater environments, especially the Great Lakes, and on efforts to control it.