Carbonate Chemistry in Groundwater and Rivers Draining to the Baltic Sea : Implications for Coastal Ocean Acidification
Börjesson, Solveig (University of Gothenburg)
Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals
Ljungberg, Wilma (University of Gothenburg)
McKenzie, Tristan (University of Gothenburg)
Reithmaier, Gloria (University of Gothenburg)
Majtényi-Hill, Claudia (University of Gothenburg)
Henriksson, Linnea (University of Gothenburg)
Holloway, Ceylena (Southern Cross University)
Yau, Yvonne Y.Y. (University of Gothenburg)
Rodriguez-Puig, Júlia (Universitat Autònoma de Barcelona. Departament de Física)
Böttcher, Michael Ernst (University of Greifswald)
Santos, Isaac (University of Gothenburg)

Fecha:	2026
Resumen:	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, δ13C-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 CO2 due to low TA/DIC ratios. Mixing plots revealed non-conservative production of TA and DIC in subterranean estuaries. δ13C-DIC values imply that organic matter respiration was a main source of DIC to northern catchments, while calcium carbonate (CaCO3) dissolution was more important along the southeastern coast. Fresh SGD contributed only < 2% of TA and DIC, and 5-7% of Ca, Mg, and SO4 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.
Ayudas:	Ministerio de Ciencia, Innovación y Universidades FPU20/01369 Agencia Estatal de Investigación CEX2019-000940-M
Nota:	Unidad de excelencia María de Maeztu CEX2024-001506-M
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Aquifer ; Blue carbon ; Carbon dioxide ; Coastal carbon ; Stable isotopes ; Subterranean estuary
Publicado en:	Estuaries and Coasts, Vol. 49 (June 2026) , art. 141, ISSN 1559-2731

DOI: 10.1007/s12237-026-01761-y

17 p, 3.0 MB

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