EVALUATION OF SUBMARINE GROUNDWATER DISCHARGE, SALINITY, AND PH TRENDS IN COMPARISON TO EASTERN OYSTER BEDS THROUGHOUT GEORGIA TIDAL CREEKS

Groundwater discharge fluxes are known to be spatially and temporally variable. They are also known to impact the biology of the receiving areas. We have been studying these variations, in addition to salinity and pH, to assess potential correlations between groundwater discharge and eastern oyster (Crassostrea virginica) beds. We collected groundwater and estuary samples at low tide from four recreational oyster harvesting creeks along the Georgia coast including Oyster Creek near Tybee Island, Medway River near St. Catherines Island, Jointer Creak near Jekyll Island and Teakettle Creek near Sapelo Island between July and October 2018. We collected pore water samples using peristaltic pumps connected to push-point piezometers driven to ~50 cm depth at locations above the low-tide line from each creek bank to determine the concentration of radon in the groundwater end-member. Groundwater discharge was surveyed from surface waters using a commercially available radon detector (RAD-7), which monitors for radon-222, a well-established tracer of groundwater discharge. We collected salinity and pH data every thirty seconds using a YSI EXO1 device. In the lab, we analyzed creek bank samples for radon within three days and corrected for humidity and decay. The survey data was processed using a transient-state mass balance box model. Groundwater discharge fluxes, salinity, pH and oyster health parameters are being compared to determine how groundwater and water chemistry impact oyster growth in Georgia’s recreational harvest areas.