Japan Geoscience Union Meeting 2016

Presentation information

Oral

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

[A-CG23] Coastal Ecosystems - 1. Water Cycle and Land-Ocean Interactions

Tue. May 24, 2016 10:45 AM - 12:15 PM 301A (3F)

Convener:*Jun Shoji(Hiroshima University), Ryo Sugimoto(Faculty of Marine Biosciences, Fukui Prefectural University), Makoto Yamada(Research Institute for Humanity and Nature), Masahiko Ono(National Institute of Advanced Industrial Science and Technology), Chair:Ryo Sugimoto(Faculty of Marine Biosciences, Fukui Prefectural University), Makoto Yamada(Research Institute for Humanity and Nature)

11:30 AM - 11:45 AM

[ACG23-09] Analysis of the coastal food web and influence of terrestrial input in Toyama Bay using δ13C and δ15N

Chihiro Urasawa1, *JING ZHANG1, Osamu Inamaura2, Shota Kambayashi1, Shohei Hattori3, Naohiro Yoshida3 (1.University of Toyama, 2.Uozu Aquarium, 3.Tokyo Institute of Technology)

Keywords:Toyama Bay, Carbon and Nitrogen stable isotope ratio, Food web

Toyama Bay is a semi-enclosed bay facing the Sea of Japan, which has a distinctive coastal environment. It receives a large amount of freshwater (such as river and submarine groundwater discharge (SGD)) and it is also affected by the Japan Sea water. In this study, to evaluate terrestrial effect on coastal organisms in Toyama Bay, we analyzed food web structure and estimate utilization situation of organic matter and nutrient (NO3-) derived from land in food web using stable isotope ratios (δ13C・δ15N ; δ15N・δ18O in nitrate).
The δ13C values of consumers (such as bivalve, crustacea and fish) in the coastal area of Toyama Bay were clearly higher than those in the riverine particulate organic matter (POM). This indicates that consumers do not use terrestrial organic matter as their carbon source. The calculated contribution of benthic microalgae to diet of consumers was about 30 - 60 %, suggesting that 13C-enriched benthic microalgae is an important carbon source for the coastal food web in Toyama Bay.
Primary producer in coastal area of Toyama Bay shows much lower δ15N values than typical primary producer in other coastal area. In addition, δ15N (NO3-) values of coastal area in Toyama Bay are also lower than the δ15N (NO3-) values of deep seawater of Toyama Bay and Japan Sea water. Low δ15N (NO3-) values were also observed in the rivers and SGD around Toyama Bay. Our results suggest that coastal organisms in Toyama Bay are influenced by terrestrial input of low δ15N (NO3-) through the rivers and SGD.