No abstract

Submarine Groundwater Discharge (SGD) is now recognized as an important pathway between land and sea. This paper takes a first step for estimating nutrient inputs through SGD to Ariake Bay. SGD rates and its quality along the coast of the Ariake Bay off Oura region were investigated. As a result, it was shown that on-site SGD rate ranged from 0.01 to 20.52µm/s, and SGD flowed through shallow confined aquifers which consist of basalt and superposition pyroclastic fall with shorter residence time. Then, it was estimated that reduction reaction for SGD proceeded just up to denitrification, and SGD associated nutrient loads (N, P, SiO 2 ) are estimated at 1.40g/day, 0.07g/day, and 52.78g/day respectively. The results of this study demonstrate that SGD must be considered as a significant source of nutrient to the coastal sea area in Ariake Bay.

Submarine Groundwater Discharge (SGD) is now recognized as a significant role to the ecology of coastal environment as well as river discharge. This paper takes a first step for highlighting nutrient transport through SGD to volcanic rock area along the Ariake Bay. SGD rates and their qualities along the coastal area of the Ariake Bay, Ohura, Saga Prefecture, Kawachi, Kumamoto Prefecture, and Fukae, Nagasaki Prefecture regions are investigated. As a result, SGD generally decreased with the distance from the shoreline except Ohura point where large seepage rate is observed. It is presumed that SGD could be classified into two types based on the rate of SGD and the geological structure. Then, it is indicated that the SGD oxidation-reduction condition varied with seepage rate and path way. The results of this study demonstrate that SGD may be considered as a significant source of nutrient to the coastal area in Ariake Bay.