Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Evening Poster

A (Atmospheric and Hydrospheric Sciences) » A-CG Complex & General

[A-CG42] Coastal Ecosystems - 1. Water Cycle and Land-Ocean Interactions

Thu. May 24, 2018 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Ryo Sugimoto(Faculty of Marine Biosciences, Fukui Prefectural University), Jun Shoji(Hiroshima University), Makoto Yamada(龍谷大学経済学部, 共同), Masahiko Fujii(Faculty of Environmental Earth Science)

[ACG42-P05] Effects of ammonium derived from hot spring drainage on riverine ecosystem in the Beppu area

Shohei Takemoto1, Ryo Sugimoto1, *Makoto Yamada2, Hisami Honda3, Taketoshi Mishima4, Shinji Ohsawa4, Jun Shoji5 (1.Reseach Center for Marine Bioresources, Fukui Prefectural University, 2.Faculty of Economics, Ryukoku University, 3.Research Institute for Humanity and Nature, 4.Institute for Geothermal Sciences, Kyoto University, 5.Hiroshima University)

Keywords:Hot spring drainage, ammonium, attached algae, Nile tilapia

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.