Development of environmental diagnostic indicators using compound-specific stable isotopic compositions for coastal marine ecosystems

利用溶解无机碳（DIC）的碳稳定同位素比值（δ^ C）沿沿着带的纵向分布，研究了河口红树林沼泽向沿岸沃茨的CO2排放<13>。通过DIC的δ^ C测量值与保守混合模型的偏差来评价红树林CO_2<13>。该方法已应用于泰国安达曼海岸的两个河口以及日本石垣岛的Nagura河口。在所研究的所有河口中，红树林的CO_2输入都被成功地定量化，河口中红树林产生的DIC浓度高达500μ M。2.利用沉积有机质的稳定碳、氮同位素比值（δ^<213>C，δ^<15>N）来评价海岸海草床中有机质的物源。此外，还详细考察了样品制备过程中的冷冻干燥和酸脱碳酸对δ^<13>C和δ^<15>N测定结果的影响。安达曼<13><15>海岸海草床沉积物的δ^ C和δ^ N表明陆源有机碳和水氮在河口海草床中的输入和积累<13>。我们的数据表明，海草碳在沉积物中的积累程度取决于该地点周围生长的海草的物种组成。我还计划在本财政年度出版一本介绍水生生态系统稳定同位素环境指标的书。

Use of stable isotopic signatures of carbon and nitrogen for assessing environmental stresses on coastal marine ecosystems has been elaborated in several different situations, among which three cases are described below.1.Emission of carbon dioxide from the estuarine mangrove swamps to coastal waters has been evaluated using longitudinal distribution of carbon stable isotope ratio (δ^<13>C) of dissolved inorganic carbon (DIC) along brackish areas. Mangrove-derived CO_2 was evaluated by deviation of measured δ^<13>C of DIC from conservative mixing model. this approach has been applied to two estuaries in Andaman coast of Thailand as well as to the Nagura estuary in Ishigaki Island, Japan. In all the estuaries examined, CO_2 input from the mangroves was successfully quantified and concentration of mangrove-derived DIC in the estuaries was up to 500μM.2.Stable carbon and nitrogen isotope ratios (δ^<213>C,δ^<15>N) of sedimentary organic mater have been used to evaluate the provenance of organic matter in coastal seagrass beds. Effects of sample preparation such as lyophilization and acid decarbonation on measured δ^<13>C and δ^<15>N were also thoroughly examined. δ^<13>C and δ^<15>N of seagrass bed sediments from Andaman coast evidenced input and accumulation of terrestrial organic carbon and waterwater-derived nitrogen in river-mouth seagrass beds.3.Contributions of seagrass-derived and terrestrial organic carbon to coastal sediments were evaluated using δ^<13>C of individual fatty acids. Our data suggested that the degree of accumulation of seagrass-derived carbon in sediments depend on species composition of seagrass that grew around the site.I have also a plan to publish an introductive book on stable isotope environmental indicators for aquatic ecosystems in the present fiscal year.