Estimating submarine groundwater discharge in Jeju volcanic island (Korea) during a typhoon (Kong-rey) using humic-fluorescent dissolved organic matter-Si mass balance

Abstract

We examined the residence time, seepage rate, and submarine groundwater discharge (SGD)-driven dissolved nutrients and organic matter in Hwasun Bay, Jeju Island, Korea during the occurrence of a typhoon, Kong-rey, using a humic fluorescent dissolved organic matter (FDOMH)-Si mass balance model. The study period spanned October 4–10, 2018. One day after the typhoon, the residence time and seepage rate were calculated to be 1 day and 0.51 m day−1, respectively, and the highest SGD-driven fluxes of chemical constituents were estimated (1.7 × 106 mol day−1 for dissolved inorganic nitrogen, 0.1 × 106 mol day−1 for dissolved inorganic phosphorus (DIP), 1.1 × 106 mol day−1 for dissolved silicon, 0.5 × 106 mol day−1 for dissolved organic carbon, 1.6 × 106 mol day−1 for dissolved organic nitrogen, 0.4 × 106 mol day−1 for particulate organic carbon, and 38 × 106 g QS day−1 for FDOMH). SGD-driven fluxes of dissolved nutrient and organic matter were over 90% of the total input fluxes in Hwasun Bay. Our results highlight the potential of using the FDOMH-Si mass balance model to effectively measure SGD within a specific area (i.e., volcanic islands) under specific weather conditions (i.e., typhoon/storm). In oligotrophic oceanic regions, SGD-driven chemical fluxes from highly permeable islands considerably contribute to coastal nutrient budgets and coastal biological production.