[A-CG35_28PO1] Land-Ocean Interaction -Water and material cycle for coastal ecosystems-

[ACG35-P04] Local scale assessment of submarine groundwater discharge in coastal seas (Beppu, Obama and Otuchi Bay)

*Honda HISAMI¹, Ryo SUGIMOTO¹, Osamu TOMINAGA¹, Shiho KOBAYASHI², Youji MIYATA², Masahiko ONO³, Shinji OHSAWA⁴, Makoto TANIGUCHI⁵ (1.Faculty of Marine Bioscience, Fukui Prefectural University, 2.Field Science Education and Research Center, Kyoto University, 3.National Institute of Advanced Science and Technology, 4.Institute for Geothermal Sciences, Kyoto University, 5.Research Institute for Humanity and Nature)

Keywords:submarine groundwater discharge, 222Rn, land-ocean interaction

Submarine groundwater discharge (SGD) is important as a major pathway for freshwater and nutrients loads from land to ocean. Various natural tracers of SGD have been applied to quantify local to regional SGD fluxes. Radon-222 (²²²Rn) is a naturally occurring radioactive gas that is typically 2-3 orders of magnitude higher in groundwater than surface waters. Therefore, it is a powerful tracer of groundwater inputs to oceans. We have applied the continuous ²²²Rn monitoring survey to three local scale coasts (Beppu Bay, Obama Bay and Otsuchi Bay), which have large amounts of groundwater resources in each watershed. As a result, spatial distributions of ²²²Rn and other parameters displayed not only influence of submarine groundwater discharge but also possibility of submarine hotspring discharge.