[A-CG42] 沿岸海洋生態系─１．水循環と陸海相互作用

[ACG42-P05] 温泉排水由来のアンモニア態窒素が別府地域の河川生態系に及ぼす影響

竹本 昌平¹、杉本 亮¹、*山田 誠²、本田 尚美³、三島 壮智⁴、大沢 信二⁴、小路 淳⁵ (1.福井県立大学海洋生物資源学部、2.龍谷大学経済学部、3.総合地球環境学研究所、4.京都大学大学院理学研究科附属地球熱学研究施設、5.広島大学大学院生物圏科学研究科)

キーワード：温泉排水、アンモニア態窒素、付着藻類、ナイルティラピア

In the Beppu area, large amounts of ammonium are supplied from hot spring drainage to the river systems. However, it is difficult to evaluate the effect of ammonium derived from hot spring drainage on riverine ecosystem due to a contamination of nitrate supplied from sewage. Using the stable isotopes of ammonium and nitrate, we have evaluated quantitative effects of ammonium on riverine primary producer as well as dominant fish, Oreochromis niloticus (Nile tilapia), in the Hirata and Haruki Rivers. Although majority of dissolved inorganic nitrogen was dominated by nitrate in the Hirata River, ammonium supplied from hot spring drainage was most important nitrogen source for attached algae as well as Nile tilapia. Contribution rate of ammonium on algal assimilation reached to around 65%. On the other hand, attached algae assimilated 96% of nitrate derived from sewage in the Haruki River, because there was little influence of hot spring drainage.