J-GLOBAL ID:200904028813977916  Research Project code:0450021932 Update date:Nov. 08, 2004

Fundamental study on origin of oxygen-free water area based on radioactive carbon analysis of individual organic molecule

Study period:2003 - 2005
Research overview:
The essence and purpose of this study are described as follows. Concretely, we aim at elucidating sequential changes of water body structure at present and in the past in detail by means of analysis of 14C and stable carbon isotope 13C as biomarkers originated in bacteria. For example, Oba et al. (1995, Paleoceanography) and Yamada et al. (1999, Geochemical Journal) suggested that the water body structure in the Japan Sea in the ice age was changed to be oxygen-free. For this event, we perform 14C analysis at a molecular level to elucidate a process of making the oceanic deep layer in the ice age oxygen-free, which is currently left as unsolved. In case that the 14C age of bacteria deposited at that time shows almost no difference from the depositing age (the foraminifer age), there is a possibility that subordinate nutrition bacteria are living by using fresh organic substances carried through basic production in the upper layer. In case that some differences are recognized, suggested is another possibility that chemical nutrition bacteria are living by using carbon dioxide being inorganic again and recycled carbon sources (methane, acetic acid, etc.) in the oceanic lower layer. A length of staying time is found from an extent of difference between the depositing age and the optimum living environment (more concretely, from data such as depth and temperature, nutrition sources, possibility of symbiosis with other bacteria) for bacteria producing biomarkers. Its sequential changes are, namely, interpreted as a process in which the ocean was changed to be oxygen-free. In such a way, we intend to elucidate oceanic changes in detail including water body structures in the past, their processes, staying times and so forth. At the same time, we apply this method to a current oxygen-free water body (samples from lakes and marshes like the Marsh Kai) as a case study. From this result, we obtain data of end members in combination of molecular-level 13C analysis and an amount of existing molecules and data of detailed ecology obtained from 14C. A quantitative relation is estimated by calculating a mass balance based on these data. From this relation, quantitative explanation becomes possible for a geochemical carbon cycle at the level of biomarkers (namely, at the level of creature species carrying carbon circulation) at present and in the past, which has been unsolved up to now. Biomarker compounds taken as targets are dipropten, a kind of hovanoid compounds, (methane-oxidizing bacteria in case of extremely low 13C, cyano-bacteria in case of high 13C), C15 branched fatty acids (sulfuric acid-reducing bacteria, gram positive bacteria) and C18:1 (1 unsaturated) fatty acid (sulfur-oxidizing bacteria). These are separately sampled by means of PCGC (partition-cell gas chromatography). Ether lipid originate from archaebacterium (archaeol and so on) is separately fractionated by LC (liquid chromatography) because of its large molecular weight. By using such a quite new method, we perform this study on the purpose of grasping changes of the environment of the earth in the past qualitatively as well as quantitatively.
Project Organization (1):
  • (C013000000)
Research program: Grant-in-Aid for Scientific Research
Ministry with control over the research :
Ministry of Education, Culture, Sports, Science and Technology

Return to Previous Page