楚科奇海浮冰区夏季短期颗粒有机物通量及其主要组分

SHORT-TERM FLUX AND COMPOSITION OF PARTICULATE ORGANIC MATTER IN PACK ICE OF CHUKCHI SEA IN SUMMER

中国首次北极科学考察期间 ,于 8月 2 0— 2 3日在楚科奇海浮冰区联合冰站实施了为期 4天的短期颗粒有机物通量研究。结果显示真光层的颗粒有机碳通量为 1 .582mgCm- 2 day- 1 ,2 2 0m深层为 1 .339mgCm- 2 day- 1 ,而相应的沉降颗粒物总通量分别高达 8.788和 1 0 .30 3mgm- 2 day- 1 。显示北极浮冰区的夏季融冰季节后期 ,颗粒有机碳通量的水平较低。与颗粒有机碳通量水平相似 ,生源硅和活性磷的通量水平也较低。对硅藻通量组份的分析表明 ,真光层沉降硅藻的优势种为Nitzschiacf.seriata、Naviculaglacialis和Melosirasp .,而 2 2 0m层则Lepto cylindrussp .占绝对优势 ,其丰度数量百分比均超过 70 %。硅藻碳通量的绝对值较低 ,为0 .1 0 7— 0 .1 1 3mgCm- 2 day- 1 。然而 ,真光层大型桡足类的碳估算值高达 1 0 8.67mgCm- 2day- 1 ,占浮游动物总碳量的 95 .3 % ,大型浮游动物的表观碳通量高于浮游植物碳通量 2— 3个数量级 ,显示楚科奇海夏季融冰期高浮游动物碳量、低浮游植物碳量的特点。但浮游动物表观碳量高的主要原因与浮游动物的昼夜垂直运动有关 。

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.