EVALUATING MULTIPLE ALGAL MONITORING METHODS AND FACTORS AFFECTING THE DISPERSAL OF COLOR PRODUCING AGENTS IN A GREAT LAKES ESTUARY

Here we present a synthesis of results from algal bloom monitoring at the Old Woman Creek (OWC) Estuary of Ohio during three consecutive summers. Composition of algal blooms were measured using algal cell counts, fluorescent spectroscopy and reflectance spectroscopy, over ten days during each summer. Varimax-rotated principal components (VPCs) of the first derivatives of reflectance data (VDS) were extracted using SPSS™. Significant correlation between the VPCs containing chlorophyll a and phycocyanin and fluorometrically measured chlorophyll a, supports the successful applicability of VDS to monitor phytoplankton assemblages. Similarly, the correlation between the VPCs containing sediments and total suspended solids (TSS) suggests the application of reflectance spectroscopy to monitor sediment assemblages at OWC. However, in contrast to an expected positive correlation, statistically significant negative correlation was observed between cyanobacteria cell counts and fluorometrically measured pigment concentrations. Significant correlations were not observed between the relative cell counts and VPCs containing phytoplankton. Counting additional cells could yield more representative data for each sample, but this will also increase the analysis time and limit the applicability of the method to larger waterbodies and sample numbers. In contrast, VDS provide a better overview of the color-producing agents in the water as it also provides an overview of TSS in the entire sample. Hence reflectance signals decomposed using VPC analysis provides a rapid overview of color producing agents in water including pigments, as well as suspended sediments. Considerable differences in sediment composition was observed, with illite resulting from the suspension of estuary floor during dry years, while smectite, chlorite and goethite washed down from the upper parts of the OWC watershed dominated during relatively wet years. Sediment and phytoplankton transportation across the estuary were controlled mainly by the wind during dry years, while runoff controlled the process during wet periods when the flow from estuary to Lake Erie is unregulated by the formation of a barrier bar. Spatial variability of the VPCs across the estuary supports the environmental significance of the estuary as a sediment sink.