Logo image
Back
Recirculated and fresh submarine groundwater discharge fluxes of dissolved carbon in a temperate seagrass lagoon
Journal article   Peer reviewed

Recirculated and fresh submarine groundwater discharge fluxes of dissolved carbon in a temperate seagrass lagoon

Yusi Wang, Bangjian Zhang, Qiangqiang Zhong, Xu Ren, Shiqing Sun, Yuda Chen, Miao Li, Ronggen Jiang, Jinzhou Du, Fenfen Zhang, …
Journal of hydrology, Vol.680, pp.1-13
11/2026
DOI: https://doi.org/10.1016/j.jhydrol.2026.136432
Appears in  Recent National Centre for Naturopathic Medicine Publications

Metrics

1 Record Views

Abstract

Blue carbon Carbon budgets Coastal carbon Seagrass meadows Subterranean estuaries
Submarine groundwater discharge (SGD) is a critical hydrological process linking coastal aquifers, sediments, and ocean waters. However, bulk SGD estimates often cannot distinguish the relative contributions of fresh submarine groundwater discharge (FSGD) and recirculated submarine groundwater discharge (RSGD) to dissolved carbon export. In this study, we employ a modified pathway-specific Ra model that separates FSGD from RSGD by contrasting mixed porewater Ra endmembers. By coupling these partitioned water fluxes with measurements of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and fluorescent dissolved organic matter (FDOM), we quantify pathway-specific dissolved carbon export within a temperate seagrass lagoon. The dual-Ra (223Ra and 224Ra) model revealed that RSGD was substantially higher than FSGD, with fluxes of 2.6 (2.2–3.3) and 0.9 (0.7–1.5) cm d-1, respectively. Porewater DIC and DOC concentrations were approximately 1.7 and 2.0 times greater than those in seawater. Consequently, RSGD accounted for approximately 82% and 87% of the total net SGD-associated DIC and DOC fluxes, respectively, corresponding to RSGD-associated area-normalized fluxes of 71 (41–101) and 12 (9–15) mmol m−2 d-1. Optical analyses further revealed that SGD transported both humic-like and protein-like fluorescent DOM components, with humic-like components dominating the exported FDOM pool. Together with the enrichment of DIC and DOC in porewater relative to seawater, these findings provide evidence that RSGD drives the advective export of carbon-enriched porewater into the lagoon. Our results demonstrate that pathway-specific separation of FSGD and RSGD is essential to attribute dissolved carbon fluxes in coastal aquifers and to properly evaluate groundwater-mediated lateral exchange in coastal blue carbon budgets.

Details

Logo image