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Lake Minnetonka Zebra Mussel Study

Project Status: 
Current Status: 

(Updated April 2016) The District began closely tracking the population of zebra mussels across Lake Minnetonka in 2011, after zebra mussels were discovered in the lake the year prior. After collecting multiple years of data the district is working to publish several research papers. Preliminary findings were presented at the North American Lake Management Society. The MCWD's intensive study of zebra mussels in Lake Minnetonka will continue. 

Snorkeler in the water looking for zebra mussels
About this project: 

Since zebra mussels were discovered in Lake Minnetonka in 2010, the District began closely monitoring the population of zebra mussels in the lake and their effect on water quality. Lake Minnetonka is a uniquely valuable place to study the effects of zebra mussels because of its variety of water types – rocky bottoms, sandy bottoms, deep areas, shallow areas, bays with clear water and bays with murky water.

Five years into the study, there have been a number of valuable findings. Existing water quality conditions, especially the abundance and type of algae in an area, appear to have a direct impact on whether or not zebra mussels thrive. Zebra mussels appear to struggle to take hold in bays with either very high or very low levels of algae – those with very high levels tend to be dominated by blue-green algae, a poor food source for the mussels, and lakes with very low content simply don't have enough food available. The invasive mussels appear to proliferate in bays with a moderate amount of algae. Changes in water quality have been observed in some bays with abundant zebra mussels.  In some bays, but not all, water clarity has increased, Chlorophyll has decreased and Phosphorus has decreased. This detailed data on how zebra mussels spread in different types of lake conditions will be valuable for predicting the severity of infestations in lakes across the state, and the impacts they may have on water quality

Zebra mussels are causing fast changes in the lake, which often lead to unpredictable effects.  Increased clarity could lead to vegetation growing deeper, production in the lake is changing that could have cascading impacts on fish communities, native mussel populations have been observed to be reduced from zebra mussels suffocating them, and changes in algal communities could eventually result in more blue-green algae blooms.  Many of these changes may not be easily observable, but are all possible long-term impacts of zebra mussels.