Dreissena bugensis Andrusov, 1897

This study provides the first evidence of a species shift within the dreissenid community to quagga mussels in the lower Great Lakes. In the eastern basin of Lake Erie, D. polymorpha is now rare and, in Lake Ontario, quagga mussels dominate in areas of lake bottom that once were mostly zebra mussels. If these trends continue, the quagga mussel might be expected to eventually colonize the upper Great Lakes and other waters as well. At present, it is possible only to speculate on what factors underlie the shift to quagga mussels in Lakes Erie and Ontario but it is clear that further work on exploitative competition, recruitment, and growth is required to better understand the population dynamics of these two sympatric dreissenids. Mills et al. (1999)

Locations of St. Lawerence River where Dreissena bugensis occurred in densities of 4,000-20,000/m2 resulted in 90-100% native unionid mortality. D. bugensis colonize unionids bivalves in high densities. Data suggests that once Dreissena mass is equal to or exceeds that of the bivalve, it will be extirpated. Unionid mortality in the St. Lawrence River appears to result primarily from the failure of heavily infested unionids to secure adequate energy stores for overwintering. Because mortality can occur at relatively low infestation levels, unionid populations in other large North American rivers are at risk of extirpation as Dreissena continues to invade new drainages.(Ricciardi et al, 1996).

There is evidence to suggest that the economic and ecological risks associated with invasion by quagga mussels are not identical to those associated with zebra mussels. Quagga mussels may be able to foul intake pipes that take in water too cold for zebra mussels to tolerate (Cornell University, 2005). Their impact on native species can also differ; Nalepa et al. (2009) monitored the benthic community in Lake Michigan and noted that the population of the native amphipod Diporeia underwent a severe decline after the zebra mussel invasion of the lake, but then stabilized. When quagga mussels began to colonize the lake they replaced most of the zebra mussels in the shallow areas, but were also able to colonize the deeper areas of the lake, which led to a further decline in the Diporeia population and extirpation of the species from much of the lake. The fact that zebra mussels are already present should not lead to complacency, therefore, about invasion by quagga mussels. (Quinn et al. 2013).