EVALUATING MULTIPLE ALGAL MONITORING METHODS AND FACTORS AFFECTING PHYTOPLANKTON DISPERSAL UNDER OPPOSING HYDROLOGICAL CONDITIONS IN A GREAT LAKES ESTUARY

Here we present 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 (YSI sonde), visible derivative spectroscopy (VDS) and quantitative polymerase chain reactions (qPCR) over ten day periods during two of the three summers. Fluorescent spectroscopy provides a rapid, quantitative assessment of chlorophyll-a and phycocyanin in water but not an assessment of sediment composition. Significant correlation between the principal components of VDS data (VPCs) containing chlorophyll a and phycocyanin (blue green algae pigments) and fluorometrically measured chlorophyll a, supports the successful applicability of reflectance spectroscopy to monitor phytoplankton assemblages. Similarly, the correlation between the VPCs containing sediments and total suspended solids suggests the application of reflectance spectroscopy to monitor sediment assemblages at OWC. Significant correlations were not observed between the relative cell count percentages and VPCs containing phytoplankton. Counting additional cells could yield more representative data for each sample, but this would also increase the analysis time and limit the applicability of the method to larger waterbodies and sample numbers. In contrast, the reflectance approach used here filtered 250 ml sample on to a 45 mm diameter filter paper and the reflectance was measured over four different quadrants of the filter paper. Hence, the reflectance signal should be much more representative of the color-producing agents in the water compared to cell counts. Therefore, the diffuse spectral reflectance followed by VPCA to decompose the reflectance signal provides a rapid overview of chlorophyll and other pigments, chlorophyll degradation products, as well as suspended sediments present in the water. Additionally, the comparison of meteorological data with algal productivity suggests that during dry periods, sediments and phytoplankton were transported across the OWC estuary by wind. In contrast, during wet years when the flow from estuary to Lake Erie is unregulated by the formation of a sandbar, transportation is controlled mainly by runoff.