EVALUATING WEEKLY VARIATION OF ALGAL BIOMASS IN THE OLD WOMAN CREEK ESTUARY USING VISIBLE SPECTRAL REFLECTANCE

The Old Woman Creek National Estuarine Research Reserve (OWC) connects the Old Woman Creek tributary with Lake Erie. In June and July, harmful algae blooms in the Lake Erie basins and feeds off of phosphorus and nitrogen from sediment and run off from surrounding areas. The wetland area of Old Woman Creek can retain some of the nutrients that would drain into the larger basins of Lake Erie. A sand barrier caused by longshore drift occasionally forms, closing the mouth bar of the estuary. The objective of this research is to determine the date(s) of peak algae production to assist in future research on algal blooms in Lake Erie. Daily surface water samples were taken over a period of two weeks at four locations in OWC, which include, DR, OL, WM, and MO. For each sample, 250 mL of water were pressure filtered onto 25mm GF/F filters in the lab at 15 psi, and oven dried for 24 hours. Visible light reflectance of each of the dried filters was measured using a Konica/Minolta CM2600d Spectrophotometer. Chlorophyll-a light absorption is strongest between 650-700 nm and can be identified as a trough in the reflectance spectrum. Area of the trough directly indicates the concentration of Chlorophyll-a. Trough areas were calculated for all the collected samples following the methods explained by Wolfe et al., (2006). Area calculations were compared with data from the NOAA NERR Centralized Data Management Office website for the OL and WM locations. The analyzed data suggests that in situ temperature and pH are roughly inversely correlated. As the dissolved oxygen in the water column dropped over the period of 14 days, the amount of chlorophyll-a increased. This decline in dissolved oxygen may be caused by net community respiration from autotrophs and heterotrophs exceeding the O₂ production from algal photosynthesis. The weight of total suspended matter on the GF/F filters indicated the fluctuation of total suspended matter in the water samples. At the OL and DR sites, the total suspended matter increased over the two-week period. While at WM, the total suspended matter fluctuated but did not have an overall increase or decrease. Total suspended matter at MO increased between days 3 and 7, but returned to the original amount by the end of the sampling.