Drivers of inorganic carbon dynamics and air–water CO2 fluxes in two large tropical estuaries: Insights from coupled radon (222Rn) and pCO2 surveys. Issue Volume 67:Issue S2(2022) (21st April 2022)

• Record Type: Journal Article
• Authors: Akhand, Anirban; Chanda, Abhra; Watanabe, Kenta; Das, Sourav; Tokoro, Tatsuki; Hazra, Sugata; Kuwae, Tomohiro
• Other Names: Santos Isaac R. guestEditor.; Hatje Vanessa guestEditor.; Serrano Oscar guestEditor.; Bastviken David guestEditor.; Krause‐Jensen Dorte guestEditor.; Mullarney Julia C. guestEditor.
• Is Part Of: Limnology and oceanography. Volume 67:Issue S2(2022)
• Page Start: S118
• Page End: S132
• Publication Date: 2022-04-21
• Subjects: Limnology -- Periodicals; Oceanography -- Periodicals; Océanographie; Limnologie; Limnology; Oceanography; Computer network resources; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); Periodicals; 551.4805
• DOI: 10.1002/lno.12075
• Languages: English
• ISSNs: 0024-3590

Abstract

Abstract: Estuaries and coastal waters are generally significant emitters of CO2 to the atmosphere. Globally, submarine groundwater discharge (SGD) is a significant driver of inorganic carbon dynamics and the partial pressure of CO2 in water [ p CO2 (water)] in estuaries and coastal waters. However, there are few studies of CO2 emission and SGD in large tropical estuaries. To investigate the drivers of p CO2 (water) dynamics in two large tropical estuaries in India, the Hooghly and Matla estuaries, we conducted coupled radon and p CO2 (water) surveys of groundwater and surface waters. We also collected high‐temporal‐resolution (1 min) data of related biogeochemical parameters. Using radon‐222 ( 222 Rn) as a proxy for SGD, we found significant regulation of p CO2 (water) by SGD in both studied estuaries. This observation can be considered direct evidence of the influence of SGD on p CO2 (water) and consequent air–water CO2 fluxes in these two previously poorly studied estuaries. Our finding that total alkalinity (TAlk) and dissolved inorganic carbon (DIC) were also significantly higher in the groundwater than in the estuarine surface waters also supports a substantial contribution of SGD to the inorganic carbon dynamics of these estuaries. However, high groundwater TAlk to DIC ratios (> 1) indicate that SGD also enhances the carbonate buffering capacity in these estuaries. By contributing to an improved understanding of the role of SGD in inorganic carbon cycling in tropical estuaries and coastal oceans, this study will contribute to efforts to upscale regional‐scale coastal carbon budgets to a global scale.