Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C/N ratios
Distribution and sources of organic matter in surficial sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C/N ratios
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DOI：
10.1016/j.marchem.2005.10.002
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发表时间：
2006-02
期刊：
影响因子：
3
通讯作者：
T. Usui;S. Nagao;Masanobu Yamamoto;Koji Suzuki;I. Kudo;S. Montani;A. Noda;M. Minagawa
中科院分区：
文献类型：
--
作者：
T. Usui;S. Nagao;Masanobu Yamamoto;Koji Suzuki;I. Kudo;S. Montani;A. Noda;M. Minagawa
测定了日本北海道十胜近海21 ~ 1995 m水深94个站位表层沉积物（0-3 cm）中有机碳（C）和全氮（N）含量及其同位素比值，以阐明沉积有机质的分布和来源。悬浮颗粒有机物（POM）在海水和悬浮POM和沉积物在十胜河进行了检查。十胜川样品的δ 13 C、δ 15 N和C/N比值表明，春季融雪是陆源有机质向沿岸沃茨迁移的重要过程。表层海水悬浮态POM的δ 13 C值在5月和11月高于8月，δ 15 N值在5月和8月高于11月。这些变化归因于浮游植物生长速率和硝酸盐可用性的季节性变化。十胜近海沉积物中的δ 13 C和δ 15 N值在十胜河口附近最低，在近海增加到恒定值，从134到1995 m水深持续存在。沉积物中C/N比值的空间变化反映了δ 13 C和δ 15 N的空间变化。通过对十胜口附近海域沉积物中δ 13 C、δ 15 N和C/N比值与十胜川和海水中有机质含量的比较，发现十胜口附近海域沉积物中约有一半有机质为陆源有机质，而134 ~ 1995 m水深的沉积物有机质为陆源有机质。沉积物中有机碳含量在十胜河口附近较高，在1000 m水深附近也较高。C含量显着相关的粉砂和粘粒含量，与不同的回归线，这些站浅，深于134米，由于几个站的C含量较高的C/N比升高的内陆架。这些结果表明，输运和沉积的有机质丰富的细泥沙颗粒的水动力过程的主要因素控制的C含量十胜。此外，一部分陆源有机质的高C/N的供应可能也影响了内陆架的C含量。
Organic carbon (C) and total nitrogen (N) contents and corresponding isotope ratios were determined in surficial sediment (0–3 cm) at 94 stations ranging from 21 to 1995 m water depth off Tokachi, Hokkaido, Japan, to elucidate the distribution and source of sedimentary organic matter. Suspended particulate organic matter (POM) in the seawater and suspended POM and sediment in the Tokachi River were also examined. δ13C, δ15N and C/N ratios of the samples in the Tokachi River suggest that the spring snowmelt is an important process for the transport of terrestrial organic matter to the coastal waters. δ13C values of suspended POM in the surface seawater were higher in May and November than in August, while δ15N values of the POM were higher in May and August than in November. These changes are attributed to seasonal changes in phytoplankton growth rate and nitrate availability. δ13C and δ15N values in the sediments off Tokachi were lowest near the Tokachi River mouth, and increased offshore to constant values that persisted from 134 to 1995 m water depth. The spatial variation in C/N ratios in the sediment mirrored those of δ13C and δ15N. Comparison of δ13C, δ15N and C/N ratios in the sediments off Tokachi with those in the Tokachi River and seawater indicates that about half of the organic matter in the sediment was of terrestrial origin near the Tokachi River mouth, and the sedimentary organic matter from 134 to 1995 m water depth was of marine origin. The organic C content in the sediment was high near the Tokachi River mouth, and also around 1000 m water depth. The C content was significantly correlated with silt plus clay content, with different regression lines for those stations shallower and deeper than 134 m, owing to several stations of higher C content with the elevated C/N ratio on the inner shelf. These results suggest that transport and deposition of organic-rich fine sediment particles by hydrodynamic processes were major factors controlling C content off Tokachi. In addition, the supply of a fraction of terrestrial organic matter with high C/N probably also affected C content on the inner shelf.