MONITORING THE WATER QUALITY AND THE TEMPORAL VARIABILITY OF PHYTOPLANKTON USING REFLECTANCE SPECTROSCOPY TO UNDERSTAND HARMFUL ALGAL BLOOMS IN THE OLD WOMAN CREEK NATIONAL ESTUARINE RESERVE, OHIO

Old Woman Creek Natural Estuarine Reserve (OWC) is a coastal wetland on the southern shores of Lake Erie. Presence of turbidity in the estuary water often interferes with direct in-situ measurement of chlorophyll concentrations. Visible derivative spectroscopy (VDS) was used to interpret the sediment and phytoplankton assemblages within the estuary. Four and six sites were sampled from the summers of 2016 and 2017, respectively. Varimax rotated principal component analysis of reflectance data (VPCA) from 2016 identified three components (VPCs): diatom+illitie and kaolinite, dinoflagellate algae +cryptomonads+ cyanobacteria, and illite+green algae+ second cyanobacteria community. Four leading components were identified from the VPCA of 2017 data, which included a diatom+green algae+cyanobacteria (VPC 1), smectitie+illite (VPC 2), and two more cyanobacteria communities each of which associated with goethite and calcite, respectively. Significant correlation between VPC 1 versus chlorophyll and VPC 2 versus total suspended solids, supports the successful applicability of VDS to monitor phytoplankton and sediment assemblages at OWC. Temporal variation of phytoplankton during the ten day sampling periods suggest that the storm runoff can significantly impact the estuary phytoplankton abundance. When the mouth bar controlling the flow from estuary to the Lake Erie is open, algal abundance in the estuary declined immediately after rainfall. In contrast, a significant decline is not observed when the mouth bar is closed, which suggests a flushing of phytoplankton through the estuary into the lake under open mouth bar conditions. Availability of nutrients washed down with the storm runoff resulted an increase in all types of phytoplankton, 2-3 days after storm events, when the mouth bar is open and closed. The inflow of storm water increased the concentration of insoluble clay minerals but decreased the concentration of calcite: associated with groundwater inflow and/or bio-induced precipitation. Suspended sediments were transported in to the lake through the estuary when the mouth bar is open. As the mouth bar narrowed by the end of 2017 sampling period, the amount of algae and suspended material transported in to the lake declined and were more concentrated in the upstream sampling sites.