delta C-13 and delta N-15 Values of Sediment-trap Particles in the Japan and Yamato Basins and Comparison with the Core-top Values in the East/Japan Sea

摘要

Investigation of sediment-trap deployments in the East/Japan Sea (EJS) showed that distinct seasonal variations in particulate organic carbon (POC) fluxes of intermediate-water sediment-traps clearly corresponded to changes in chlorophyll a concentrations estimated from SeaWiFS data. The prominent high POC flux periods (e.g., March) were strongly correlated with the enhanced surface-water phytoplankton blooms. Deep-water sedimenttraps exhibited similar variation patterns to intermediate-water sediment-traps. However, their total flux and POC flux were higher than those of intermediate-water sediment-traps during some months (e.g., April and May), indicating the lateral delivery of some particles to the deep-water sediment-traps. Distinct seasonal delta C-13 and delta N-15 variations in settling particles of the intermediate-water sediment-traps were observed, strongly supporting the notion of seasonal primary production. Seasonal variations in delta C-13 and delta N-15 values from the deep-water sediment-traps were similar to those of the intermediate-water sediment-traps. However, the difference in delta C-13 and delta N-15 values between the intermediate-water and the deepwater sediment-traps may be attributed to degradation of organic matter as it sank through the water column. Comparison of fluxweighted delta C-13 and delta N-15 mean values between the deep-water sediment-traps and the core-top sediments showed that strong selective loss of organic matter components (lipids) depleted in C-13 and N-15 occurred during sediment burial. Nonetheless, the results of our study indicate that particles in the deep-water sediment-trap deposited as surface sediments on the seafloor preserve the record of surface-water conditions, highlighting the usefulness of sedimentary delta C-13 and delta N-15 values as a paleoceanographic application in the EJS.