Carbonate Chemistry and the Potential for Acidification in Georgia Coastal Marshes and the South Atlantic Bight, USA

Janet J Reimer; Patricia M Medeiros; Najid Hussain; Stephen F Gonski; Yuan-Yaun Xu; Ting-Hsuan Huang; Wei-Jun Cai

doi:10.1007/s12237-023-01261-3

Carbonate Chemistry and the Potential for Acidification in Georgia Coastal Marshes and the South Atlantic Bight, USA

Estuaries Coast. 2024;47(1):76-90. doi: 10.1007/s12237-023-01261-3. Epub 2023 Sep 11.

Authors

Janet J Reimer^{1

2}, Patricia M Medeiros³, Najid Hussain¹, Stephen F Gonski¹, Yuan-Yaun Xu^{1

4}, Ting-Hsuan Huang^{1

5}, Wei-Jun Cai¹

Affiliations

¹ School of Marine Science and Policy, University of Delaware, Newark/Lewes, DE USA.
² Mid-Atlantic Regional Council on the Ocean, PA, USA.
³ Department of Marine Sciences, University of Georgia, Athens, GA USA.
⁴ Planetary Technologies, Dartmouth, NS Canada.
⁵ Department of Oceanography, National Sun Yat-Sen University, Kaohsiung, Taiwan.

Abstract

In coastal regions and marginal bodies of water, the increase in partial pressure of carbon dioxide (pCO₂) in many instances is greater than that of the open ocean due to terrestrial (river, estuarine, and wetland) influences, decreasing buffering capacity and/or increasing water temperatures. Coastal oceans receive freshwater from rivers and groundwater as well as terrestrial-derived organic matter, both of which have a direct influence on coastal carbonate chemistry. The objective of this research is to determine if coastal marshes in Georgia, USA, may be "hot-spots" for acidification due to enhanced inorganic carbon sources and if there is terrestrial influence on offshore acidification in the South Atlantic Bight (SAB). The results of this study show that dissolved inorganic carbon (DIC) and total alkalinity (TA) are elevated in the marshes compared to predictions from conservative mixing of the freshwater and oceanic end-members, with accompanying pH around 7.2 to 7.6 within the marshes and aragonite saturation states (Ω_Ar) <1. In the marshes, there is a strong relationship between the terrestrial/estuarine-derived organic and inorganic carbon and acidification. Comparisons of pH, TA, and DIC to terrestrial organic material markers, however, show that there is little influence of terrestrial-derived organic matter on shelf acidification during this period in 2014. In addition, Ω_Ar increases rapidly offshore, especially in drier months (July). River stream flow during 2014 was anomalously low compared to climatological means; therefore, offshore influences from terrestrial carbon could also be decreased. The SAB shelf may not be strongly influenced by terrestrial inputs to acidification during drier than normal periods; conversely, shelf waters that are well-buffered against acidification may not play a significant role in mitigating acidification within the Georgia marshes.

Supplementary information: The online version contains supplementary material available at 10.1007/s12237-023-01261-3.

Keywords: Carbonate chemistry; Coastal acidification; Dissolved inorganic carbon; Total alkalinity; pCO2.