Groundwater releases CO<sub>2</sub> to diverse global coastal ecosystems.
Where this comes from
- Record sourced from PubMed, PMID 39792679.
- Also identified by DOI 10.1126/sciadv.adr3240 and PMC identifier 11721568.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Coastal ecosystems play a major role in marine carbon budgets, but substantial uncertainties remain in the sources and fluxes of coastal carbon dioxide (CO<sub>2</sub>). Here, we assess when, where, and how submarine groundwater discharge (SGD) releases CO<sub>2</sub> to shallow coastal ecosystems. Time-series observations of dissolved CO<sub>2</sub> and radon (<sup>222</sup>Rn, a natural groundwater tracer) across 40 coastal systems from 14 countries revealed large SGD-derived CO<sub>2</sub> fluxes. The mean groundwater partial pressure of CO<sub>2</sub> was 35 times higher than surface seawater. The mean SGD-derived CO<sub>2</sub> flux was 148 ± 226 millimoles per square meter per day (mmol m<sup>-2</sup> day<sup>-1</sup>), resulting in a mean water-air CO<sub>2</sub> flux of 80 ± 133 mmol m<sup>-2</sup> day<sup>-1</sup>. Tidal rather than diel cycles drove CO<sub>2</sub> enrichment in most ecosystems. Tidally driven SGD was the primary CO<sub>2</sub> source in mangroves, salt marshes, tidal flats, estuaries, and canals. Overall, we expand current knowledge of marine carbon cycles by demonstrating SGD as an important source of CO<sub>2</sub> that requires inclusion in coastal carbon budgets.