[A-CG53] Coastal Ecosystems - 1. Water Cycle and Land-Ocean Interactions

[ACG53-03] Significance of submarine groundwater discharge in Ise Bay using radium isotopes

*Ryo Sugimoto¹, Yuitsu Tochio¹, Toshimi Nakajima², Makoto Okada³, Tomohiko Kobayashi³, ATSUYOSHI MANDA⁴ (1.Faculty of Marine Biosciences, Fukui Prefectural University, 2.Atmosphere and Ocean Research Institute, The University of Tokyo, 3.Mie Prefecture Fisheries Research Institute, 4.Mie University)

Keywords:Submarine groundwater discharge, Radium, Nutrient

Recent studies revealed that the nutrient supply from groundwater inflow to coastal waters is comparable to that from surface river water worldwide. Here, we conducted field surveys to assess the submarine groundwater discharge of fresh groundwater and recirculated groundwater into Ise Bay using radium isotopes (²²³Ra; τ_1/2=11.4 days, ²²⁴Ra; τ_1/2=3.66 days, ²²⁶Ra; τ_1/2=1600y, and ²²⁸Ra; τ_1/2=5.75y). The results showed that the freshwater groundwater inflow was on average about 0.4 times higher than the river water inflow and the recirculating groundwater inflow was 1.3 times higher than the river water inflow. In the presentation, we will show the results of nutrient fluxes associated with groundwater inflow.