Date of Award

Spring 5-1-2024

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Angelos Hannides

Second Advisor

Susan Libes

Third Advisor

April Abbott

Additional Advisors

Danielle Viso, Victoria Green, Janet J. Reimer, Emily R. Hall

Abstract

One of the major water-quality issues impacting our coast and estuaries is coastal-ocean and estuarine acidification. Due to a relative dearth of data in the southeastern United States it is increasingly difficult to determine the full extent and intensity of this problem. This study provides the first characterization of coastal-ocean and estuarine acidification in Long Bay, SC by attempting to leverage long-term water quality data sets at two coastal-ocean pier sites using in-situ YSI EXO sondes deployed at both the surface and bottom waters along with two estuarine sites sampled by volunteer monitors using Orion star multi-meters. Discrete samples (120) for Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TA) were collected from July 2022 to February 2023 contemporaneously to current routine observations at our four sites using the methods of Reimer et al. (2017). DIC and TA were measured according to Wang and Cai (2004). CO2SYS was used to calculate pCO2, free [H+], pHT, ΩCA and ΩAR. Property-property plots (pHNBS vs. pHT, TA vs. Salinity and pHT vs. Salinity, Temperature and Dissolved Oxygen) were compared using geometric mean regression. Sensor pHNBS measurements were compared to calculated pHT measurements. Data show that DIC and TA peaks coincide with Chl a increases and DO decreases which indicates respiration taking place and adding CO2 into the system (Schulz and Riebesell 2013). Oyster Landing and Rum Gully Creek both had values that fell within the pHT, pCO2, ΩCA and ΩAR thresholds for Eastern Oysters (Gobler and Talmage 2014) and Summer Flounder (Chambers et al. 2014) indicating periodic events where they could be experiencing acidification events detrimental to their development. The estuarine sites showed strong linearity at Oyster Landing and Rum Gully Creek. No strong linear relationships were found between TA and salinity due to a highly dynamic coastal system. Current methodologies used by the volunteer monitoring program, at the estuarine sites, shows pHNBS can potentially act as a proxy for pHT. However, due to the lack of a conservative relationship between TA and salinity more information is needed to identify potential acidification trends. Future studies should be done to obtain more observations and sampling to better identify potential acidification trends (Pimenta and Grear 2018). Due to the highly dynamic nature of these systems future sampling should also include measuring pHT from discrete samples in the laboratory to compare CO2SYS calculated pHT to the discretely measured pHT to help identify areas of error (Dickson et al. 2007, Fassbender et al. 2017). There should be a future focus on the need for better and more holistic data collection (i.e. nutrients, carbonate parameters, water quality parameters, etc.) in order to better understand and describe potential acidification in these estuarine and coastal-ocean systems.

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