JpGU-AGU Joint Meeting 2017

講演情報

[JJ] ポスター発表

セッション記号 A (大気水圏科学) » A-CG 大気水圏科学複合領域・一般

[A-CG50] [JJ] 沿岸海洋生態系──2.サンゴ礁・藻場・マングローブ

2017年5月24日(水) 10:45 〜 12:15 ポスター会場 (国際展示場 7ホール)

コンビーナ:宮島 利宏(東京大学 大気海洋研究所 海洋地球システム研究系 生元素動態分野)、梅澤 有(長崎大学)、渡邉 敦(東京工業大学 環境・社会理工学院)

[ACG50-P01] Dissolved carbon dynamics in rivers and coastal areas of the Philippines: evaluation of terrestrial inputs using dissolved inorganic carbon stable isotopic composition

*Naoko Morimoto1Atsushi Watanabe2Yu Umezawa3Maria Lourdes San Diego-McGlone4Charissa M. Ferrera4Toshihiro Miyajima1 (1.Department of Chemical Oceanography, Atmosphere and Ocean Research Institute, The University of Tokyo、2.Department of Transdisciplinary Science and Engineering, School of Environment and Society, Tokyo Institute of Technology, O-okayama 2-12-1 W8-13 Meguro, Tokyo 152-8552, Japan、3.Faculty of Fisheries, Nagasaki University, 1-14 Bunkyo, Nagasaki 852-8521, Japan、4.Marine Science Institute, University of the Philippines, Diliman, Quezon City 1101, Philippines)

キーワード:terrestrial inputs, stable isotopic composition, dissolved inorganic carbon, particulate organic matter, tropical coastal area

River load of anthropogenic materials is one of key sources for degradation of coastal habitats as with aquacultures. They change coastal water quality directly and indirectly, and local multiple organic sources such as mariculture fish feeds/feces, resuspended sediment and coral mucus complicate those influences. To assess the effect of allochthonous inputs, isotope signatures of dissolved inorganic carbon (DIC) and particulate organic matter (POM) were examined to identify sources and their loading processes. In Bolinao, where mariculture is densely deployed in semi-closed embayment, δ13C-DIC and δ13C-POC values of river water were almost similar between the wet and dry seasons, and were decreased as decreasing salinity. However, the relationship between δ13C-DIC and δ13C-POC was unclear. In the coastal area, large decrease of salinity was observed in the wet season. The negative correlation between salinity and each parameter suggests that river inputs mainly decreased δ13C-DIC (–5.8‰ ~) and δ13C-POC (–28.5‰ ~) in the wet season. In the dry season, mariculture, maybe fish feeds/feces, was mainly attributed to the decrease of δ13C-DIC values especially in the surface layer through their decomposition. In contrast, in Iloilo, where some rivers input to the strait among islands, the character of river δ13C-DIC and δ13C-POC was similar as Bolinao. In coastal area, the decrease of δ13C-DIC was not so serious in the wet season (–1.4‰ ~) compared to Bolinao, however low δ13C-POC value was observed in the bottom layer (–27.7‰ ~). It may be ascribed to resuspension of settled materials which was originated from river inputs. We try to unravel their underlying multiple processes and discuss the relationship between river and coastal area in terms of dissolved carbon dynamics in those areas.