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

点击翻译按钮获取中文摘要

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.