Environmental DNA as a tool to help inform zebra mussel, Dreissena polymorpha, management in inland lakes

Zebra mussels (Dreissena polymorpha) are an aquatic invasive species that plague much of North America and are difficult to impossible to eradicate once they become established. Therefore, prevention and monitoring are key elements in the control of these organisms. Traditional microscopy is commonly used in monitoring but requires the presence of larval veligers. This limits the times when resource managers can monitor for the presence in northern lakes. A new monitoring tool, environmental DNA (eDNA), may allow for a more efficient and cost-effective monitoring program for zebra mussels. We developed and tested an environmental DNA assay in the fall and spring for zebra mussels in two Minnesota lakes, one heavily infested and another newly infested. We found that DNA copy numbers tended to be higher near the lake bottom and DNA was more concentrated in softer substrates. We also found that the amount of zebra mussel DNA sampling in winter resulted in similar results to when sampled in fall. This suggests that one could collect and analyze eDNA for zebra mussels during winter months to help inform future efforts in monitoring and control.