夏季の東京湾における懸濁態および堆積有機物の炭素安定同位体比(<特集>東京湾およびその集水域内の物質循環)

概要

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The carbon isotopic characteristics (δ^<13>C) of particulate organic matter during the summer blooming in Tokyo Bay have been investigated. The δ^<13>C of suspended particulate organic matter (POM) in the surface seawater ranged from -15.4‰ to -4.5‰, which were considerably higher than the value generally known of planktonic organic matter (-20±1‰), suggesting that actively growing phytoplankton might be subjected to such a condition that the diffusion rate of CO_2 might strongly limit the production of organic carbon. However, the isotope ratios of surfacial sedimentary organic matter ranged from -20.4‰ to -18.1‰, which were lower than those of POM. The δ^<13>C of sinking organic particles collected in sediment traps were similar to those of POM. Therefore, the ^<13>C-enriched isotope characteristics produced during summer phytoplankton blooming might be unlikely to be conserved in the sediments, possibly, by being mixed with terrestrial organic matter depleted in ^<13>C, and/or, being rapidly decomposed during their sedimentation process. In conclusion, it was strongly suggested that properly determining the marine-endmember of δ^<13>C should be important if the δ^<13>C would be principally used to estimate contributions of terrestrially and in situ produced organic matter in such an exceedingly eutrophic coastal area as Tokyo Bay.
日本地球化学会の論文
1994-03-24