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EFFECTS OF PLANT SENESCENCE ON WATER QUALITY IN A SMALL, SEMI-ISOLATED FRESHWATER WETLAND

Abstract

Water quality is a function of concomitant physicochemical conditions and biological processes. Such conditions and processes may include: rainfall, contaminant sources, atmospheric conditions, flora, and fauna. In small water bodies, aquatic vegetation and algal communities can serve a disproportionate role in biogeochemical cycles because these systems do not regularly mix with other surface water inflows and outflows. Seasonal photosynthetic activity drives dissolved oxygen / carbon dioxide dynamics which in turn drive pH cycles. Fall senescence may drive important water quality changes in small wetlands through cessation of growing season photosynthesis and influx of coarse organic matter (e.g. leaf litter). Our objective is to quantify changes in water quality related to plant senescence in a small, semi-isolated, freshwater wetland on Saint Simons Island, GA. A Hydrolab MS5 sonde was used to measure dissolved oxygen, pH, specific conductivity, and temperature weekly beginning 10/19/2018 (prior to plant senescence) through 11/30/2018 (late stages of senescence). Turbidity was measured using a HACH 2100Q turbidimeter for the same period of record. Preliminary findings show dissolved oxygen increased during plant senescence, likely due to decreasing temperatures. Specific conductivity decreased which may be caused by increased precipitation diluting soil water inputs during late autumn. Turbidity and pH have not yet shown a response to plant senescence. Measurements will continue through the winter and into the next growing season. Small, freshwater wetlands on barrier islands are understudied relative to nearby saltmarshes. Therefore, our findings provide baseline conditions to compare future water quality monitoring in small semi-isolated wetlands on the Georgia Coast.

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