Quagga mussels pose problems similar to zebra mussels. They clog intake pipes for water treatment and power generating plants, encrust boat motors and hulls, and their sharp shells cut beach-goers’ feet. Ecologically, they filter enormous quantities of microscopic algae and divert energy flow through aquatic ecosystems, with potential impacts on fish populations that may exceed those of zebra mussels.
Current research at MAISRC focuses on characterizing the total microbial community structures associated with quagga mussels to determine if they have any potential biocontrol options. Click here to download a factsheet about quagga mussels.
About quagga mussels
“Quagga mussel” is the common name given in North America to Dreissena rostriformis “bugensis,” a close relative of the zebra mussel D. polymorpha. The two species have much in common, including a similar native range, morphology, life style, life history, and physiology, so this description focuses on the differences between the two species, with special attention paid to the potential implications of these differences for Minnesota invasions of this mussel.
Quagga mussels have become a growing problem in North America for two primary reasons. First, while their expansion in our waterways was slightly delayed, they have replaced zebra mussels at most locations in southern Lake Michigan and most of Lake Erie. They now dominate lake-bottom environments in the lower Great Lakes and have become far more abundant in deeper waters (>100 feet) than zebra mussels ever were. Secondly, they have successfully spread long distances overland, having reach waters of the Colorado River system (Lake Mead and downstream) and are therefore of great concern in the western U.S.
What they are and what they look like
Quagga mussels are bivalve molluscs that tend to be slightly larger and thinner-shelled than zebra mussels. They have a more rounded shape to their shell, which is often marked by alternating darker bands in “rings” rather than the zigzag pattern seen on many zebra mussel shells. One distinguishing feature is the “flatness” of the ventral surface of the shell. When placed on this side, a zebra mussel will sit flat, while a quagga mussel will tip over. There are other features – including molecular genetic differences – which experts can use to distinguish between the two species.
Quagga mussels have a very similar life cycle to zebra mussels, although quagga mussels are able to spawn at lower temperatures, survive with lower concentrations of planktonic food, and live at greater depths.
Where they're found
Quagga mussels are native to the Black Sea drainage of southwestern Russia. Canal-building in Europe spread them over the continent similar to zebra mussels, but at a slower rate. They were first identified in North America in 1994, but examination of older specimens showed that the first introductions overlapped with zebra mussels, in the mid- to late- 1980s. Quagga mussels have been far less successful at spreading to inland lakes, both in Europe and North America, although in the long-term that should not serve as the basis for relaxed vigilance. In Minnesota, quagga mussels first were found in Duluth Harbor in 2005 and in the Mississippi River (at low densities) in 2008. As of 2016, they have not been reported in any additional lakes and rivers in the state, with the only known reproductive population being in the Duluth Harbor.
How they spread
The potential pathways for spread are very similar to those for zebra mussels. Both zebra and quagga mussels use byssal threads (pictured at right) to attach to surfaces. Recent studies from the lower Great Lakes show that, even in regions where quagga mussels dominate the lake bottom, zebra mussels are better at attaching to and spreading on recreational watercraft.Although this explains their overall faster spread, we must remember that quagga mussels reached Lake Mead from sources far to the east, meaning that overland spread is not only possible, but that it has already happened. And their ecological replacement of zebra mussels in the Great Lakes warns us to pay close attention to this newer invasive mussel in Minnesota.
Quagga mussel research at MAISRC
The Sadowsky Lab is characterizing the total microbial community associated with quagga mussels across time and space to see if any pathogenic relationships occur that could be developed into a biocontrol for this invasive invertebrate. Samples will be collected from several water bodies where there are new AIS invasions, sudden changes of population density, or die-off events occurring. After dissection and observation, DNA will be obtained from all organs and tissues using DNA extraction kits. Water and sediment samples will also be collected near the sites to determine their influence on the microbial community.
- First hurdle cleared in search for microbial biocontrol agents against AIS (MAISRC newsletter)
- Early detection tool developed for invasive mussels and their larvae (MAISRC Newsletter)
Byssal theads, used for movement and attaching to hard surfaces.