Mortality of Zebra Mussels, Dreissena polymorpha, in an Enclosure Experiment in Gull Lake, Michigan
Scheurer, Allison Claire
MetadataShow full item record
Since their introduction to the Great Lakes in 1986, Dreissena polymorpha (zebra mussel) has proven itself to be a very hearty species. It has shown great migratory capacity, niche variability, and reproductive strategies in the invasion of lakes, rivers and canals from St. Lawrence River to the Mississippi River. Zebra mussels thrive in both lotic and lentic systems, eutrophic and oligotrophic waters, and even brackish waters. Zebra mussels are filter feeders, feeding primarily on phytoplankton, and may alter phytoplankton distribution, abundance, and species diversity where the zebra mussel density is large. This study worked along side a zebra mussel experiment (ZMEX 2001) designed to determine different zebra mussel densities' affect on phytoplankton communities in a large inland lake in southwest Michigan, Gull Lake. The study sought to monitor the survival of the zebra mussel densities throughout the ZMEX enclosure experiment. The ZMEX experiment relied on this study for significant results in that without a high survival of zebra mussels the densities for the phytoplankton experiment would not be reliable and the experiment could not be evaluated. The study found an unexpected high mortality of zebra mussels. It was subsequently hypothesized that stress of handling, starvation, unsuitable conditions due to oxygen and/or pH levels, and/or thermal stress may be related to enclosure mortality. Thus five null hypotheses were formulated, and data processed in an attempt to understand the reason(s) for this mortality rate. Hypotheses of stress of handling, starvation and unsuitable oxygen or pH levels did not show a significant detrimental effect on the mortality of the zebra mussels. Thermal stress had a significant effect on morality, increasing as temperatures increased. However, the temperatures within the enclosures was not greater than the lethal limit for North American mussels, leading to the conclusion that some other factor not tested for during the study was the cause of the high mortality of the zebra mussels during the experiment.