Journal article
Carbonate Chemistry in Groundwater and Rivers Draining to the Baltic Sea: Implications for Coastal Ocean Acidification
Estuaries and coasts, Vol.49(5), pp.1-17
09/2026
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Abstract
Terrestrial inputs can alter total alkalinity (TA) and dissolved inorganic carbon (DIC) of the coastal ocean and modify seawater pH. Here, we first characterize the carbonate system in river and groundwater draining to the Baltic Sea using observations of TA, DIC,
δ<sup>13</sup>C-DIC, and major ions across 6 countries and 17 beaches. We then assess whether submarine groundwater discharge (SGD) may impact coastal acidification. TA and DIC concentrations were about 2 times greater in groundwater than river water. 84% of the groundwater and 72% of river samples showed potential to acidify receiving Baltic Sea waters and degas CO<sub>2</sub> due to low TA/DIC ratios. Mixing plots revealed non-conservative production of TA and DIC in subterranean estuaries. δ<sup>13</sup> C-DIC values imply that organic matter respiration was a main source of DIC to northern catchments, while calcium carbonate (CaCO<sub>3</sub> ) dissolution was more important along the southeastern coast. Fresh SGD contributed only < 2% of TA and DIC, and 5–7% of Ca, Mg, and SO<sub>4</sub> fluxes compared to river discharge when extrapolated to the entire Baltic Sea. However, unquantified total SGD (fresh groundwater plus recirculated seawater) water and chemical fluxes are likely higher. Overall, SGD can locally acidify the Baltic Sea and should be considered in regional carbon budgets.
Details
- Title
- Carbonate Chemistry in Groundwater and Rivers Draining to the Baltic Sea: Implications for Coastal Ocean Acidification
- Creators
- Solveig Börjesson - University of GothenburgWilma Ljungberg - University of GothenburgTristan McKenzie - University of GothenburgGloria Reithmaier - University of GothenburgClaudia Majtényi-Hill - University of GothenburgLinnea Henriksson - University of GothenburgCeylena Holloway - Southern Cross UniversityYvonne Y. Y. Yau - University of GothenburgJúlia Rodriguez-Puig - Universitat Autònoma de BarcelonaMichael Ernst Böttcher - Leibniz Institute for Baltic Sea Research WarnemündeIsaac R. Santos - University of Gothenburg
- Publication Details
- Estuaries and coasts, Vol.49(5), pp.1-17
- Publisher
- Springer Nature; NEW YORK
- Grant note
- Funding was provided by the Knut and Alice Wallenberg Foundation (2022-0096), a Swedish Research Council grant (2020 − 00457) and a Formas Early Career Researcher grant (2023 − 01324). Open access funding provided by University of Gothenburg.
- Identifiers
- 991013386429302368
- Copyright
- © The Author(s) 2026.
- Academic Unit
- National Marine Science Centre; National Centre for Naturopathic Medicine
- Language
- English
- Resource Type
- Journal article