TY - JOUR
T1 - Molecular and isotopic abundances of long-chain n-fatty acids in open marine sediments of the western North Pacific
AU - Naraoka, Hiroshi
AU - Ishiwatari, Ryoshi
N1 - Funding Information:
The crew of R/V Hakuho-Maru and scientists on board are acknowledged for their cooperation in sampling LM sediments. SR sediments were kindly donated by Dr. S. Montani. Dr. K. Yamada is acknowledged for assistance of isotope measurement for n-alkanes and useful comments. The authors thank Drs. J.K. Volkman, M. Conte, D. Brincat and S.R. Poulson for improving the manuscript. This work was supported by the Grant-in-Aid for Scientific Research from the Japanese Ministry of Education, Science and Culture, and Nissan Science Foundation grant (HN). [JD]
PY - 2000/4/4
Y1 - 2000/4/4
N2 - Molecular abundance and compound-specific carbon isotope ratios of long-chain n-fatty acids (LCFAs) ranging from C20 to C30 are reported for open marine sediments of the western North Pacific. A positive correlation (r2 = 0.94) is observed between total organic carbon (TOC) and LCFA concentrations, although the TOC concentrations varied from 0.34 to 2.62 (wt.% in dry sediment). The relatively uniform ratio of LCFAs to TOC (0.74 ± 0.12 mg/gC) is similar to that of the central Pacific reported by Ohkouchi et al. [Ohkouchi, N., Kawamura, K., Kawahata, H., Taira, A., 1997. Latitudinal distributions of terrestrial biomarkers in the sediments from the Central Pacific. Geochim. Cosmochim. Acta 61, 1911-1918] and in a core sample from the tropical central Pacific by Prahl et al. [Prahl, F.G., Muehlhausen, L.A., Lyle, M., 1989. An organic geochemical assessment of oceanographic conditions at MANOP site C over the past 26,000 years. Paleoceanography 4, 495-510]. On the other hand, LCFA concentrations in riverine and estuarine sediments are apparently higher than in open marine sediments. Carbon isotopic compositions of individual LCFAs in open marine sediments are similar (-26 ± 1‰ for n-C24 and n-C26), being more enriched in 13C than bay and riverine sediments by up to 6‰. Terrestrial C3 higher plants commonly have a δ13C value of ~ -26‰ in bulk organic carbon, and because lipid components including fatty acids are known to be depleted in 13C by several per mil compared to bulk organic matter, this study indicates that the open marine sedimentary LCFAs are not derived from normal terrestrial C3 higher plants. Rather, the isotopic composition is consistent with a mixed source of C4 and C3 terrestrial higher plants, and/or marine organisms. Low carbon preference index (CPI) values of the LCFAs, and the isotopic difference between the northern and southern samples suggest that the LCFAs of this study are likely to be related to marine primary productivity, even though LCFAs have often been used to infer a terrestrial higher plant input to marine sediments. (C) 2000 Elsevier Science B.V. All rights reserved.
AB - Molecular abundance and compound-specific carbon isotope ratios of long-chain n-fatty acids (LCFAs) ranging from C20 to C30 are reported for open marine sediments of the western North Pacific. A positive correlation (r2 = 0.94) is observed between total organic carbon (TOC) and LCFA concentrations, although the TOC concentrations varied from 0.34 to 2.62 (wt.% in dry sediment). The relatively uniform ratio of LCFAs to TOC (0.74 ± 0.12 mg/gC) is similar to that of the central Pacific reported by Ohkouchi et al. [Ohkouchi, N., Kawamura, K., Kawahata, H., Taira, A., 1997. Latitudinal distributions of terrestrial biomarkers in the sediments from the Central Pacific. Geochim. Cosmochim. Acta 61, 1911-1918] and in a core sample from the tropical central Pacific by Prahl et al. [Prahl, F.G., Muehlhausen, L.A., Lyle, M., 1989. An organic geochemical assessment of oceanographic conditions at MANOP site C over the past 26,000 years. Paleoceanography 4, 495-510]. On the other hand, LCFA concentrations in riverine and estuarine sediments are apparently higher than in open marine sediments. Carbon isotopic compositions of individual LCFAs in open marine sediments are similar (-26 ± 1‰ for n-C24 and n-C26), being more enriched in 13C than bay and riverine sediments by up to 6‰. Terrestrial C3 higher plants commonly have a δ13C value of ~ -26‰ in bulk organic carbon, and because lipid components including fatty acids are known to be depleted in 13C by several per mil compared to bulk organic matter, this study indicates that the open marine sedimentary LCFAs are not derived from normal terrestrial C3 higher plants. Rather, the isotopic composition is consistent with a mixed source of C4 and C3 terrestrial higher plants, and/or marine organisms. Low carbon preference index (CPI) values of the LCFAs, and the isotopic difference between the northern and southern samples suggest that the LCFAs of this study are likely to be related to marine primary productivity, even though LCFAs have often been used to infer a terrestrial higher plant input to marine sediments. (C) 2000 Elsevier Science B.V. All rights reserved.
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U2 - 10.1016/S0009-2541(99)00159-X
DO - 10.1016/S0009-2541(99)00159-X
M3 - Article
AN - SCOPUS:0034603676
VL - 165
SP - 23
EP - 36
JO - Chemical Geology
JF - Chemical Geology
SN - 0009-2541
IS - 1-2
ER -
