The role of submarine groundwater discharge (SGD) in nutrient budgets of Gamak Bay, a shellfish farming bay, in Korea

In order to evaluate the main source of nutrients fueling primary production in a shellfish farming bay (Gamak Bay) in the southern sea of Korea, we measured the concentrations of nutrients and radium isotopes in stream water, surface seawater, and coastal groundwater in May 2006, August 2006, and November 2007. Using a 226Ra mass balance model, submarine groundwater discharge (SGD) into the bay was estimated to be 1.2–1.8 × 107 m3 d− 1 (8–12 cm d− 1) during the three sampling periods. SGD-driven nutrient fluxes were approximately 85–90% and 10–30% of the total input fluxes for dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorous (DIP), respectively. The estimated nutrient budgets show that almost all the groundwater-borne nutrients were utilized inside the bay. Thus, our study suggests that the biological production of this shellfish farming bay is controlled mainly by SGD-driven nutrients.