11:30 〜 11:45
[ACG23-09] 炭素・窒素安定同位体比を用いた富山湾沿岸の食物網の解析と陸域からの影響把握
キーワード：富山湾、炭素・窒素安定同位体比、食物網
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.
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.