Assessment of the effect of submarine groundwater discharge on the biological production by the radon tracer in Wakasa-Reinan basin area

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We estimated the input of freshwater and nutrients via submarine groundwater discharge (SGD) into Obama Bay using mass balance model of radon (222Rn) and salinity. As a result, the volume of SGD into the bay was estimated to be 4-44% of the faction of SGD in total freshwater flux. The SGD tended to be high in summer, because river water discharge decreased drastically. The nutrient fluxes from SGD were approximately 39%, 58% and 37% of total terrestrial fluxes dissolved inorganic nitrogen, dissolved inorganic phosphorous and dissolved inorganic silicate, respectively. The phosphorous supply from SGD was suggested to be important in the biological production in Obama Bay which was under the phosphorous limit for primary production.