Characterizing Temporal and Spatial Scales of Coastal-Ocean and Estuarine Acidification in Long Bay, South Carolina

Coastal ocean and estuarine acidification is a major global water-quality issue impacting biological resources and therefore affecting both recreational and commercial uses of coasts and estuaries. The waters of the southeastern United States are no exception to this significant global growing concern, but the relative dearth of data from this region hinders our ability to assess the extent and intensity of the problem. This is particularly true in the case of South Carolina. To remedy this situation, we are evaluating current in-situ monitoring conducted at two coastal-pier stations and two estuarine stations in Long Bay, South Carolina. The pier time series data exhibit significant periods of low pHNBS associated with low oxygen (< 4.0 mg/L, levels stressful to marine life) and hypoxia (<2.0 mg/L) during the "hypoxia season" (June to October). Low oxygen and hypoxic conditions are present episodically for time periods of hours to days depending on the duration of physical conditions, most importantly, upwelling and favorable winds. Similarly, data collected bimonthly at a nearby estuarine setting, Murrells Inlet, as part of a volunteer water quality monitoring program exhibit similar concomitant low pH and low oxygen. The existing datasets indicate a pH range at our study sites that is sufficiently large compared to the pHNBS sensor measurement resolution of 0.01 units. For this reason, in the future, our federally funded project aims to test whether the generated pHNBS and ancillary data can enable the tracking of long-term acidification trends. Ongoing sampling for dissolved inorganic carbon (DIC) and total alkalinity (TA), contemporaneously with sensor readings, will provide information that can be used in the future to determine the mechanistic drivers of acidification in coastal and estuarine South Carolina waters. Measurement of pHT, DIC and TA, followed by validation, internal consistency, and identification of uncertainties, in the future could allow for the implantation of the methods used in this project at other pHNBS sensor-sites across the state. Increasing the number of monitoring locations will greatly enhance our understanding of acidification and its drivers.