Zebra Mussels
Since their introduction in the late 1980s, zebra mussels (Dreissena polymorpha) have spread rapidly to all of the Great Lakes and an increasing number of inland waterways throughout the United States and Canada. As we have noticed throughout our Northern Michigan lakes, these freshwater bivalves colonize anywhere they can attach their tiny byssal threads. Many lake residents have indicated that thick colonies have attached to their docks, boat hulls, and water intake pipes. They are highly prolific reproducers; female zebra mussels can produce 1 million eggs per year!
The sheer number of zebra mussels in combination with their feeding habits has caused severe disruptions in aquatic ecosystems. Each zebra mussel is capable of filtering a liter of water per day; thus, removing almost every microscopic aquatic plant and animal (phytoplankton and zooplankton). This ecosystem disruption impacts aquatic organisms throughout the food chain, from tiny crustaceans to large trout. The effect of their feeding habits is easily discernable in water transparency data collected by volunteers, which shows that water has become clearer in lakes infested with the mussels. Increased water clarity has lead to yet another impact from zebra mussels; sunlight penetrates to greater depths and results in increased growth of rooted aquatic vegetation and bottom-dwelling algae.