[A-CG23] 沿岸海洋生態系─１．水循環と陸海相互作用

[ACG23-P04] 日本沿岸海域における海底湧水インパクトの異なる場所での一次生産速度の比較

*杉本 亮¹、北川 勝博¹、西 沙織¹、本田 尚美²、山田 誠²、小林 志保³、小路 淳⁴、大沢 信二⁵、谷口 真人²、富永 修¹ (1.福井県立大学海洋生物資源学部、2.総合地球環境学研究所、3.京都大学フィールド科学教育研究センター、4.広島大学大学院生物圏科学研究科、5.京都大学大学院理学研究科附属地球熱学研究施設)

キーワード：一次生産速度、ラドン222、海底湧水、沿岸海域

In recent years, a number of studies have shown that submarine groundwater discharge (SGD) is an alternative nutrient pathway and can drive primary production in coastal seas. However, very little is known about an exact relationship between input of groundwater and response of primary production. To clarify the relationship, we conducted in situ measurements of primary productivity using stable ¹³C tracer method under different strength sites of SGD in the Japanese coasts (Site A: Obama Bay, Site B: Beppu Bay and Site C: the coastal area of Mt. Chokai) in summer from 2013 to 2015. Simultaneously, ²²²Rn activity was measured as SGD index. ²²²Rn activity in Site A, B and C varied from 0.8 to 6.0 dpm L^-1, 3.6 to 11.2 dpm L^-1 and 0.4 to 444.5 dpm L^-1, respectively. In situ primary productivity in Site A, B and C ranged from 7.0 to 49.5 μg C L^-1 h^-1, 10.7 to 38.4 μg C L^-1 h^-1 and 0.8 to 11.8 μg C L^-1 h^-1, respectively. In site A, there was significant relationship between in situ primary productivity and ²²²Rn activity. Although light intensity and water temperature were different in each station and month, concentrations of nutrients limited primary productivity. In site B and C, concentrations of dissolved inorganic nitrogen and phosphorus showed significant increasing trends with an increase of ²²²Rn activity, indicating nutrients in coastal regions were mainly derived from the SGD. However, there were no clear relationships between in situ primary productivity and ²²²Rn activity, since primary production would be limited by light intensity as well as nutrients. Our experimental studies clearly showed that nutrients through the SGD affect crucial impact on primary production in coastal ecosystems.