Abstract:

During the Chinese First Arctic Research Expedition (July September, 1999), short term particulate organic matter flux was studied in the pack ice zone in Chukchi Sea from August 20 to 23. Results of analyzing trap samples show that POC flux was 1.582mg C m -2 day -1 at euphotic layer and 1.339mg C m -2 day -1 at 220m; while mass flux was 8.788mg C m -2 day -1 at euphotic layer and 10.303mg C m -2 day -1 at 220m. It indicates that POC flux level was very low during late summer ice melting season in the pack ice zone in Chukchi Sea, so were biogenic silicon and particulate phosphate flux in that area. Diatom cells were common components in the trap samples, but diatom flux was quite low. A marked feature of the sinking diatom component was that there existed large differences between the dominant species composition at the euphotic layer and that at the deep layer of 220m. Among the sinking diatom cells, Nitzschia cf. seriata, Navicula glacialis and Melosira sp. dominated at euphotic layer, but Leptocylindrus sp. predominated at 220m. In both layers these dominant diatoms accounted for over 70% in the total diatom abundance quantitatively. But the absolute diatom carbon fluxes were only 0.107 and 0.113mg C m -2 day -1 respectively at above two layers. In contrast, the estimated carbon flux of large copepods (>330μm) was high to 108.67mg C m -2 day -1 , making up 95.3% of the total macro zooplankton carbon flux. The fact that apparent carbon flux of macro zooplankton was 2 3 orders magnitude higher than phytoplankton carbon flux, displays an obvious feature of high zooplankton carbon and low phytoplankton carbon in the water column in the ice melting duration in Chukchi Sea. Obviously, the high apparent zooplankton carbon flux was directly relative to the day night vertical movement of zooplankton, not to the actual carbon amount delivered into deep ocean.