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The Weeders Digest - Articles > Invasion of the Zebra Mussel in the United States

Invasion of the Zebra Mussel in the United States

Amy J. Benson
National Biological Service
Charles P. Boydstun
National Biological Service
Passage of the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 called for a national program to control and reduce the risk of further introductions of nonindigenous aquatic nuisance species. This legislation specifically addressed the non-native zebra mussel (Dreissena polymorpha), which is expected to affect two-thirds of the nation's waterways.
The zebra mussel, a European species, was first discovered in Lake St. Clair in June 1988 and is now well established in North America. Zebra mussel introductions through ballast water may be responsible for many other introductions to the Great Lakes as well.
Aside from economic impacts, there could also be severe biological impacts. Plankton populations are directly affected by zebra mussels because of the tremendous filtering capacity of large mussel colonies; this could potentially shift system energetics and reduce available food resources for higher organisms. Biologists in the Great Lakes region believe that zebra mussels have already had an effect on the ecology of Lake St. Clair (Griffiths 1993); increased water clarity there potentially could cause a shift in the fish species composition. There has also been a detrimental effect on native mussel populations in Lake Erie since the arrival of zebra mussels (Masteller and Schloesser 1991). Native freshwater mussels are affected when zebra mussel larvae settle and attach on native mussels, covering them so completely that they can no longer carry out life processes. In addition, zebra mussels reduce the amount of food and possibly oxygen available to native mussels.
One important part of the nonindigenous program is to monitor the zebra mussel's distribution and provide technical assistance to other federal agencies, states, and the private sector. The National Biological Service's Southeastern Biological Science Center (SBSC) in Gainesville, Florida, monitors the zebra mussel as part of this program. By using the zebra mussel as a prototype species, personnel at SBSC also began developing a national geographic information system (GIS) to organize a coherent set of nonindigenous aquatic species data.
Federal, state, and private cooperators supplied us with information, resulting in the most complete digital data set of zebra mussel sightings in North America (Boydstun and Benson 1992). The locations of sightings were then entered into a data base. Since July 1991, between the United States and Canada we have collected more than 1,000 records of zebra mussel occurrences going back to their discovery in 1988 in Lake St. Clair.
Types of Observations
Zebra mussels are observed and collected by artificial substrate samplers, plankton nets, and inspection of pipes and water intakes. In the Great Lakes pipes and water intakes at power plants, water-treatment facilities, and various industries pump lake water into their plants. Zebra mussels clog these water pipelines, causing serious mechanical problems. The U.S. Coast Guard found zebra mussels on navigational buoys in the Great Lakes during routine inspections; these buoys now serve as an artificial substrate sampler, giving us hundreds of records each winter. Zebra mussels have also been collected inadvertently while sampling for fish when using gill nets or when collecting native mussels. The incidental finds account for many important sightings in newly expanded areas.
Range Expansion
Fig. 1. States with zebra mussel sightings in inland or adjacent waters, 1988. In 1989, they spread to Lake Superior, Lake Michigan, and Lake Ontario (National Biological Service, unpublished data).
Since the first zebra mussel was sighted in 1988 (Fig. 1), the species quickly colonized regions in all five Great Lakes by 1990. Currently, they have been reported in the waterways of 19 states and 2 Canadian provinces (Fig. 2). They are established in the Great Lakes and the following rivers: Mississippi, Arkansas, Illinois, Ohio, Tennessee, Cumberland, Hudson, Susquehanna, Ottawa, Niagara, Mohawk, Genesee, Kanawha, and St. Lawrence. Established colonies exist throughout the lower Great Lakes (Erie, Ontario, and St. Clair) wherever there is suitable habitat. Lake Huron has populations in Saginaw Bay and at the southern end of the lake where it flows into the St. Clair River. There are also a few isolated populations around the lake and in the Georgian Bay area. Zebra mussels are abundant in most of the southern portion of Lake Michigan's shoreline from Sheboygan, Wisconsin, to Frankfort, Michigan. The northern portion of the lake has populations in Green Bay, Traverse Bay, and in the lake at Escanaba and St. Ignace, Michigan. Zebra mussels have also been found in 11 inland lakes in Michigan. Lake Superior is the only Great Lake where zebra mussels are not spreading quickly. Since the first sightings in Duluth Harbor in October 1989, they have been found only in Thunder Bay (Canada), Sault Ste. Marie, and Marquette, Michigan.
Fig. 2. Numbers of states affected by zebra mussels since their arrival in the United States in the mid-1980's.
The first sighting in the Mississippi River was in Alton, Illinois, on 10 September 1991. Two days later a single zebra mussel was found about 764 km (475 mi) upstream at La Crosse, Wisconsin. In January 1992, mussels were found at Clarksville, Missouri; Oquawka, Illinois; and Genoa, Wisconsin. In July 1992, mussels were reported near Winona, Minnesota. By early 1993 (Fig. 3), almost every lock and dam in the Upper Mississippi River north of Dubuque, Iowa, had zebra mussels. The Lower Mississippi River was colonized more recently in the later part of 1992 and early 1993. Mussels were collected in the river at Greenville and Vicksburg, Mississippi, in 1992. By the end of June 1993, zebra mussels were collected in Louisiana at Shaw, Lettsworth, St. Francisville, New Orleans, and Berwick.
Fig. 3. States with zebra mussel sightings in inland or adjacent waters in 1993. The range has extended west of the Mississippi River into Oklahoma by way of the Arkansas River (National Biological Service, unpublished data).
It is important to be aware of the spread of nonindigenous species, especially ones with the potential to be an ecological menace such as the zebra mussel. The natural means of dispersal is larval drift downstream. Aside from natural mechanisms, canals and barge traffic in navigable rivers are suspected as major vectors for dispersal. In April 1992, a barge dry-docked for repairs at Hartford, Illinois, had more than 1,000 zebra mussels attached to a section of exposed hull (Keevin et al. 1992). The total number of zebra mussels on the entire hull could not be determined. The barge's log book showed that it had traveled 20,558 km (12,777 mi) up and down the Mississippi River from Minnesota to Louisiana in just over 1 year before dry-docking. This documented long-distance transport of live mussels gives credibility to the assumption that barge traffic has been a primary dispersal mechanism in navigable waters. Zebra mussels can also be dispersed overland, especially by human activities such as recreational boating. Dead zebra mussels from Lake Erie were found on a boat trailer entering California (D. Peterson, California Department of Water Resources, personal communication).
For further information:
Amy J. Benson
National Biological Service
Southeastern Biological Science Center
7920 NW 71st St.
Gainesville, FL 32606

Boydstun, C.P., and A.J. Benson. 1992. Nonindigenous report (1992:1): zebra mussel (Dreissena polymorpha) sightings in the United States and Canada. National Fisheries Research Center, Gainesville, FL. 10 pp.

Griffiths, R.W. 1993. The changing environment of Lake St. Clair. Proceedings of the Third International Zebra Mussel Conference, Toronto, Canada.

Keevin, T., R. Yarbrough, and A. Miller. 1992. Inadvertent transport of live zebra mussels on barges: experiences in the St. Louis District, Spring 1992. Zebra Mussel Research Tech. Notes ZMR-1-07. U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, MS. 4 pp.

Masteller, E.C., and D.W. Schloesser. 1991. Infestation and impact of zebra mussels on the native unionid population at Presque Isle State Park, Erie, Pennsylvania. Page 20 in Proceedings of the Second Annual Zebra Mussel Research Conference, Rochester, NY.

Amy J Benson

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