Effects of Dreissena polymorpha and Pyganodon grandis on algal density

Abstract

Invasive species often compete with native species for various resources. This study investigated how an invasive species in Douglas Lake, the zebra mussel, and a native species, freshwater clams, would impact algal communities through their feeding habits. We set up aquaria with different treatments of clams and zebra mussels in the boatwell at the University of Michigan Biological Station (UMBS) and monitored algal populations through chlorophyll-a levels. The zebra mussel treatment had the highest chlorophyll-a levels and the zebra mussel and clams treatment had the lowest chlorophyll-a levels on Day 4. The higher levels of chlorophyll-a may be due to the selective feeding of zebra mussels while the lower levels of chlorophyll-a may be due to the non-selective feeding of native clams. Our findings may be useful to understand how zebra mussels are affecting algal populations and how that may in turn affect native clam populations.