Reporting that quagga mussels continue to be “major drivers and stressors” within the lake’s aquatic ecosystem, aquatic scientists assigned to the United States Environmental Protection Agency’s (USEPA) 180-foot Lake Guardian research vessel who recently completed their once every five-year survey of Lake Michigan have concluded that although the population of the exotic invasive mussels appears to have leveled off, the rapidly reproducing member of the Dreissena mussel family is becoming larger, and is occupying deeper areas of the lake’s basin. Enabled by the capacity to attach themselves to hard surfaces ranging from water intake pipes to the hulls of shipwrecks as well as to soft sediments, the filter feeding mussel, a native of the waters of Eastern Europe, now occupies more than one half of Lake Michigan’s 22, 406 square mile basin. According to scientists working aboard the vessel, the recently completed survey of the lake’s basin reaffirms that exotic invasive quagga mussels (scientific name: Dreissena bugensis) have become the dominant factor in Lake Michigan’ aquatic ecosystem.
First discovered in the Laurentian Great Lakes region in Lake St. Clair in 1988, quagga mussels represent one of two species of Dreissena mussels, the other being the now widespread zebra mussel (Dreissena polymorpha), that each entered the region via the ballast water discharges of trans-oceanic freighters navigating into the region through the St. Lawrence Seaway. Since their initial discovery over thirty years ago, quagga mussels have spread rapidly throughout Great Lakes and Mississippi River Basin states, and several other watersheds located throughout the eastern, central, and western United States, including the Colorado River, and Lake Mead, located in Nevada and Arizona. Both quagga and zebra mussels are capable of being introduced to other water bodies via microscopic larvae that are easily transported in ballast water, bilges, live wells, and other on-board equipment that holds water.
Although quagga mussels are capable of tolerating salinities of up to five parts per thousand, they have evolved to prefer the calcium carbonate rich freshwaters found in all of the Laurentian Great Lakes except Lake Superior. Unlike zebra mussels that prefer water temperatures ranging from 68° to 77° F (20° to 25° C), quagga mussels have evolved to prefer significantly cooler water temperatures ranging from 59° to 68° F (15° to 20° C). It is also known that water temperatures of 82° F (28°C), or greater begin to produce high mortality rates in quagga mussels. In contrast to zebra mussels that are more likely to be found thriving in near shore shallow water areas hosting higher water temperatures, quagga mussels are more likely to be found occupying off shore areas of the basin hosting water depths of up to 500 feet (152 meters), and inherently colder water temperatures.
Although the long term ecological effects of trillions of quagga mussels feeding upon the microscopic aquatic plants and animals that form the basis of the food chain in most lakes and rivers are not yet well understood, scientists working aboard the R/V Lake Guardian are concerned that an astronomical population of filter feeding quagga mussels are in fact gradually depleting a once abundant aquatic food chain that has a long history of supporting a robust Laurentian Great Lakes fishing industry. Moreover, the economic cost of managing the steadily escalating harmful influences of an extraordinary abundant population of exotic invasive Dreissena mussels is $500 million per year. Exotic invasive Dreissena mussels reduce the operational efficiency of power and waste water treatment plants by clogging water intake pipes, and are having an increasing negative influence upon the Great Lakes region’s lucrative recreation boating and sport fishing industries by completely covering docks, breakwalls, buoys, boats, and beaches. Littering beaches with millions of sharp edge shells, removing dead mussels from public beaches has also become a significant expense for municipal governments.
