Zebra Mussels

Matt Altstiel
5/05/05
Lab Sec#5

Clogging the Great Lakes

Zebra Mussels pose one of the largest ecological problems in the United States today and represent one of the most dangerous invasive species to arrive in the Great Lakes region. To understand the complex problem that Zebra Mussels pose, it is crucial to know the biological advantages in reproduction and environmental adaptations that have allowed it spread so quickly. It is also important to know where it came from, why it is here, and what can be done to combat its expansion. Ecological questions pertaining to: natural competition, selection of habitat, natural predators, and the role of humans in aiding or inhibiting population growth must be addressed as well. Only after answering such questions can proper discussion of control and reclamation take place.

The Zebra Mussel’s biology includes several traits that allow it to thrive and infest the Great Lakes region. Unlike most mussels which, brood their eggs within specialized gill brood pouches, Zebra Mussels “release sperm and eggs directly into the surrounding waters for external fertilization,” (Mackie et al., 1989). This allows Zebra Mussels to develop into free swimming larva in safe, nutrient rich water. After only eight to ten days, the larva are fully grown Zebra Mussels which can attach themselves to any thing if there is a current less than two meters a second, (Lyakhov, 1968). A single mature Zebra Mussel can produce anywhere from 30,000 to over 1,600,000 eggs per year! This natural reproductive advantage allows for the development of enormous colonies very quickly. Another natural advantage is the Zebra Mussel’s ability to produce dense clusters of population that crowd out any competition. The nail sized mollusk can pack a square meter under average conditions with between 5,000 to 30,000 individuals, (Griffiths et al., 1989). The Zebra Mussel tolerates most temperate waterways provided the water has low salinity content. Such natural advantages make controlling the pest a formidable task.

The Zebra Mussel has not always clogged North American waterways and has only been a part of the Great Lakes ecosystem for the last fifteen to twenty years. The original home for the Zebra Mussel is the Caspian and Black Sea regions of West and Central Asia. The species ability to attach themselves onto nearly every underwater surface allowed it to enter the ballast of ships and emerge in the freshwater harbors of the Great Lakes when ballast water was released. Fishing activities, fresh water plant imports and recreational equipment have also been credited to its introduction to the United States, (Kinzelbach, 1992; Morton, 1993). In 1988, Zebra Mussels were first sighted in sizeable numbers in Lake Saint Clare near Detroit. Since then, it has spread through the Great Lakes and into the Mississippi River, its tributaries and numerous smaller lakes and bodies of water. No natural barriers really exist to counter its invasion and only human control and caution prevents it spread. The Zebra Mussels steady expansion throughout the United States suggests a general pattern of dispersion; gaining a foothold and expanding where ever possible, (Ram and McMahon, 1996).

In little more than fifteen years, the Zebra Mussel has gone from an unknown Mussel that did not exist in North American water ways, to a one of the biggest menaces to fresh water fisheries and underwater infrastructure today. Such a rapid expansion, suggests that the Zebra Mussel population and extensity is increasing at a faster rate than every before. As a species, the mussel can thrive nearly anywhere there is temperate fresh water and therefore has no preference for either disturbed or undisturbed habitats. The Zebra Mussels rapid reproductive and high concentrations allow them out compete native Mussels, fishes and plants because it eats all the tiny plankton that feed and supports other links in the food chain. The species has not encountered any noteworthy resistance in terms of native predators or competing native mussel species. However, the “round goby, Neogobius melanostomus, itself a native of the Black and Caspian seas and also introduced into the Great Lakes via ship ballast, tends to feed preferentially on zebra mussels,” (Ghedotti, Smihula and Smith, 1995). Humans have by and large aided the expansion of the species through shipping and recreation boating that brings boats carrying Zebra Mussels into new bodies of water. Recent prevention methods and the emergence of a predatory species have not slowed the spread as quickly or as effectively as hoped.

Therefore, the Zebra Mussel poses significant environmental problems. Its reproductive advantages and huge densities allow for quick colonization of new areas very rapidly. The absence of a major predator as well as viable competition has permitted the Zebra Mussel travel from the ballast water in ships from the Caspian Sea region of central Asia, to the Great Lakes and Mississippi Basin in the United States. The problem is wide spread environmental problem that has only been worsened by human activities, and in order to effectively combat the growing problem of Zebra Mussels, human awareness and intervention are crucial.

Works Cited

Ghedotti, M. J., J. C. Smihula, and G. R. Smith. 1995. Zebra Mussel Predation By Round Gobies In The Laboratory. J. Great Lakes Res. 21(4):665-669. International Assoc. Great Lakes Research.

Griffiths, R.W., W.P. Kovalak, and D.W. Schloesser. 1989. The Zebra Mussel, Dreissena Polymorpha (Pallas, 1997), In North America: Impact On Raw Water Users. In: EPRI Service Water System Reliability Improvement Seminar: Papers. Electric Power Research Institute, Palo Alto, California. Pp. 11-27.

Kinzelbach, R. 1992. The Main Features Of The Phylogeny And Dispersal Of The Zebra Mussel Dreissena Polymorpha. In D. Neumann And H.A. Jenner Eds., The Zebra Mussel Dreissena Polymorpha. Pp. 5-17. Gustav Fisher Verlag, New York, NY.

Lyakhov, S.M. 1968. Work Of The Institute Of Biology Of Inland Waters, Academy Of Sciences Of The USSR. In B.K. Shtegman Ed., Biology And Control Of Dreissena. Israel Program For Scientific Translations Ltd., IPST Cat. No. 1774, Jerusalem, Israel. Available From The United States Department Of Commerce, National Technical Information Service, Springfield, V

Mackie, G. L., Gibbons, W. N., Muncaster, B. W., and Gray, I. M. 1989. The zebra mussel, Dreissena polymorpha: A synthesis of European experiences and a preview for North America. Toronto: Queens Printer for Ontario.

Pallas. “Fact Sheet for Dreissena Polymorpha.” http://nis.gsmfc.org/nis_factsheet.php?toc_id=131

Ram, J.L. And R.F. McMahon. 1996. Introduction: The Biology, Ecology, and Physiology Of Zebra Mussels. American Zoologist 36(3):239-243.