The effects of zebra mussels (Dreissena polymorpha) presence on rock substrate benthic algal concentrations in inland lake systems.

Abstract

In this study, we observed rocks with different types of zebra mussel influence in a freshwater lake and lab setting to determine whether benthic algal concentrations are greater on rocks are with the presence of both live and dead zebra mussels compared to rocks without any zebra mussel influence, and whether live zebra mussels promote greater algal growth than dead shells. We set up experimental plots containing rocks with live zebra mussels, with no zebra mussels, and with dead zebra mussel shells in both the littoral zone of Douglas Lake and in a stream trough in Lakeside Lab at the University of Michigan Biological Station. After 11 days, chlorophyll a analysis was conducted to determine benthic algal concentrations. There was no significant difference between benthic algal concentrations on rocks with live or dead zebra mussels and rocks without zebra mussels in the lab, but these same values were significant in the field study. The mean amount of chlorophyll a on rocks with live or dead zebra mussels was 1.3 μg/square cm, while there were 0 μg/square cm of chlorophyll a on rocks without zebra mussels. There was no significant difference between benthic algal concentrations on rocks with live zebra mussels and rocks with dead zebra mussel shells in either the lab or field study. From the results of this study, we concluded that the presence of live or dead zebra mussel shells results in greater benthic algal growth than areas without zebra mussels. We also concluded that the presence of live zebra mussels does not promote more benthic algal growth than dead zebra mussel shells.