DETERMINING THE COMPOSITION AND TRANSPORTATION OF SUMMER 2017 ALGAL BLOOMS IN OLD WOMAN CREEK ESTUARY OF LAKE ERIE USING REFLECTANCE SPECTROSCOPY

Old Woman Creek Natural Estuarine Reserve (OWC) is a coastal wetland in the southwestern shores of Lake Erie. Seasonal formation of a mouth bar controls the flow from OWC to Lake Erie. In mid-July, 6 locations within OWC were sampled for 10 days when the mouth bar was open. Water samples (250ml) were filtered through 0.4 μm GF/F filter paper. Visible color reflectance of oven dried filters was measured using a Minolta 2600D spectrophotometer. Filters were weighed before and after drying to calculate the mass of total suspended solids (TSS). Varimax-rotated principal component analysis was conducted to determine the varimax-rotated principal components (VPC). VPCs were compared to known mineral and/or pigment spectra using stepwise linear regression to find the contributing pigment(s) or mineral(s) for each VPC. To verify the VPCs, chlorophyll measurements were conducted using a chlorophyll sonde. Four VPCs were identified that explained 99% of the data variance. VPC 1 and 2 comprises chlorophyceae + diatoms + cyanobacteria and smectite + chlorite respectively. VPC 3 and 4 is goethite + dinoflagellates + cyanobacteria and calcite + dinoflagellates + cyanobacteria.

Strong correlations between all four components for two adjacent sites suggest the transport of sediment and algae across the estuary. Strong correlations between VPC 1 vs. chlorophyll concentrations, and VPC 2 vs. TSS, across all sites confirm the presence of algal matter and mineral matter in VPC 1 and 2, respectively. VPC 1 correlates with dissolved oxygen concentrations presumably due to the release of oxygen by photosynthesis. Negative correlation between VPC 2 and chlorophyll concentrations suggests that turbidity lowers the primary productivity. VPC 3 correlates with TSS at four sampling sites suggesting that goethite dominates VPC 3 at these sites. Strong correlation between rainfall and TSS suggests suspended sediment is mobilized by precipitation driven runoff. One day of lag time between TSS and total rainfall at the mouth bar suggests that sediment is transported to the mouth bar after significant rainfall. By the end of the study, flow from OWC to Lake Erie was decreasing as the mouth bar closed. VPCs 1, 3 and 4 showed a decreasing trend at the lake, adjacent to the mouth bar, suggesting that OWC plays a key role in transporting algae to the lake.