[A-CG40] Coastal Ecosystems - 1. Water Cycle and Land-Ocean Interactions

[ACG40-04] Estimation of contribution rate of Submarine Groundwater Discharge to Ulva pertusa using nitrogen stable isotope ratio analysis

*Tatsuhiro Ishida¹, Masaru Takeuchi¹, Toshimi Nakajima¹, Ryo Sugimoto¹, Shiho Kobayashi², Keisuke Koba³, Keitaro Fukushima³, Osamu Tominaga¹ (1.Fukui Prefectural University, 2.Kyoto University, 3.Center for Ecological Research,Kyoto Univrsity)

Keywords:Submarine Groundwater Discharge, Biological production, δ15N

In recent years, the influence of Submarine groundwater discharge (SGD) has attracted attention as a source of nutrient that supports biological production in the coastal area. However, the information about the direct influence of SGD on biological production is poor. In this study, in order to examine how much the groundwater contributes to primary production, we collected the primary producer Ulva pertusa in Yuza, Yamagata Prefecture, where the groundwater is abundant. On August 27, 2018, we collected sea water, ground water and ambient water around Ulva at five sites in the Yuza Coast and simultaneously measured salinity, water temperature, ²²²Rn concentration which is the indicator of undergroundwater. We also analyzed the nutrient concentration, of sampled water and of Ulva. Finally, we estimated the contribution of groundwater to Ulva using two source Bayesian Mixing model. The value of nitrate nitrogen derived from SGD was low. In the high SGD sites (²²²Rn concentration 427 ~ 22000 Bq/m³) and the low SGD sites (²²²Rn concentration 38.1 to 210.6 Bq/m³), the of Ulva was 2.1 to 3.6 and 5.4 to 6.9, respectively. It was suggested that nutrient derived from SGD contributed to the production of Ulva in Yuza.