Analysis of Factors Affecting Zebra Mussel ( Dreissena polymorpha) Growth in Saginaw Bay: A GIS-Based Modeling Approach

A statistical model was developed using a Geographical Information System (GIS) to investigate the spatial relationships between limnological variables and the growth of zebra mussels ( Dreissena polymorpha) in Saginaw Bay, Lake Huron, as defined by the change in biomass over a specified time. The presence of suitable substrate was an important factor for zebra mussel habitat, making inner Saginaw Bay an area of high mussel abundance. Temperature, phytoplankton biomass (measured as chlorophyll a), and total suspended solids (TSS) as food particles were considered to be the most important limnological variables affecting growth of zebra mussels. Three layers of attributes were developed from these variables, and were overlaid in a GIS environment according to their respective weighting factors, which were calculated in statistical analysis of spatially-matched data. The model results showed that chlorophyll a contributed the most to mussels’ growth. The effect of chlorophyll a on Dreissena growth was 9 times more important than that of temperature. The shallow portions of the inner bay and the areas in proximity to the shorelines were found to be the most suitable growth regions. A comparison of model predictions with field data on growth of mussels at various spatial locations of the inner bay demonstrated the value of this model. In addition, the model was field-tested for temporal variation in the rate of change of Dreissena biomass at one sampling station where data were available. The developed GIS-based statistical model provides a rapid, objective, reliable and cost effective tool to prioritize locations of Dreissena growth.