Radiocarbon and stable carbon isotope compositions of organic compound classes in sediments from the NE Pacific and Southern Oceans |
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| Institution: | 1. Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan;2. Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan;3. Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba, Ibaraki 305-8567, Japan;4. Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka, Kanagwawa 237-0061, Japan;5. National Institute of Technology, Ibaraki College, 866 Nakane, Hitachinaka, Ibaraki 312-8508, Japan;6. Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan;1. Institute of Marine Science, Shantou University, Shantou 515063, China;2. State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361002, China;3. State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou 570228, China;4. University of Washington Cooperative Institute for Climate, Ocean, and Ecosystem Science, 7600 Sand Point Way NE, Seattle, WA 98115, United States of America;1. Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia;2. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania 7001, Australia;3. CSIRO Oceans and Atmosphere Flagship, Hobart, Tasmania 7001, Australia |
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| Abstract: | Radiocarbon (Δ14C) abundance and stable carbon isotope (δ13C) compositions were measured for total lipid, total hydrolyzable amino acids (THAA), total carbohydrates (TCHO), and acid-insoluble organic fractions separated from phytoplankton, zooplankton, and sediment cores collected from two abyssal sites, one in the northeast (NE) Pacific Ocean and one in the Southern Ocean. These results are compared with those obtained for a separate core from the NE Pacific and reported by Wang et al. Geochim. Cosmochim. Acta 62 (1998) 1365.]. An uncharacterized acid-insoluble fraction dominated (43–57%) the sediment TOC pool at both sites. Sediment collected from the NE Pacific exhibited higher TOC, TN. and higher Δ14C values and contained both labile (THAA and TCHO) and refractory (lipid and acid-insoluble) fractions. In contrast, sediment from the Southern Ocean had much lower TOC and Δ14C values, which indicated that organic matter was extremely refractory. Sedimentation rates calculated from 14C ages of TOC for both sites indicate that the differences in the organic composition and Δ14C signatures of organic matter in the sediments likely resulted from the differences in production and deposition of organic matter to the sediment, and the diagenetic stages of sedimentary organic matter in the two oceans.Unlike Δ14C, stable carbon isotopic (δ13C) compositions of TOC in the sediments of the two oceans had similar values, which reflect not only the organic matter input from marine-derived sources but also the nature of degraded, predominately uncharacterized organic fraction in these sediments. The differences in δ13C values among the compound classes in sediments at both sites can be attributed to the carbon isotopic signatures in original sources during photosynthesis and associated environmental factors. Preferential degradation of organic matter and heterotrophic effects may also play important roles for the observed δ13C variations and these effects need to be further investigated. |
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