白令海表层沉积物中放射虫的深度分布特征及其海洋学意义

DEPTH DISTRIBUTION PATTERN OF RADIOLARIANS IN SURFACE SEDIMENTS OF THE BERING SEA AND THEIR OCEANOGRAPHIC IMPLICATIONS

中国首次北极科学考察在白令海高生产力的“白令海绿带”下方采取的表层沉积物样品中放射虫组合的研究显示,这一放射虫组合的优势种为Stylochlamydiumvenustum,Spongotrochusglacialis和Antarctissa?sp.,三者的总和超过放射虫总数的50%。放射虫含量的深度分布表明,大部分属种在100—500m的深度明显增加,显然是对陆坡至陆架边缘上部水体中高生产力的“白令海绿带”的响应。并由此推断,Stylochlamydiumvenustum,Spongotrochusglacialis,Ceratospyrisborealis和Actinommaboreale等属种主要生活于500m以上水域,并与高生产力的“白令海绿带”相关,可以作为表层生产力的替代物。而Siphocampearachnea,Cycladophoradavisiana,Stylatractuspyriformis和Pseudodictyophimusgracilipes等主要生活于500m以下冷的中层水至深层水中,可以作为中层水和深层水的替代物。白令海陆坡上部至陆架边缘高的有机碳、蛋白石含量和硅质微体化石丰度指示了高的表层生产力,是“白令海绿带”的替代物,为研究“白令海绿带”的变化及其地质历史提供了可靠依据。

Radiolarians from twelve surface sediment sites, which are located below the high productivity “Bering Sea Green Belt” (BSGB) in the Bering Sea, recovered by the box core equipment during the First Chinese National Arctic Expedition are studied. The dominant species of this radiolarian assemblage are indicated by Stylochlamydium venustum,Spongotrochus glacialis and Antarctissa ? sp., whose shell number exceeds 50 percent of total number. Depth distribution pattern of the radiolarian compositions shows that most of them increase obviously at the depth interval of 100 to 500 meters, which reveals a response to the high productivity BSGB above the slope to shelf margin. It follows that Stylochlamydium venustum,Spongotrochus glacialis,Ceratospyris borealis and Actinomma boreale live mostly above the depth of 500 meters and are related to the high productivity BSGB, serving as a proxy of surface productivity and that Siphocampe arachnea,Cycladophora davisiana,Stylatractus pyriformis and Pseudodictyophimus gracilipes dwell chiefly in the intermediate and deep waters below the depth of 500 meters, usable as a proxy of the intermediate and deep waters in the Bering Sea. Following the radiolarians from the shelf edge and upper slope are high TOC and opal and total siliceous microfossil abundance, all attributable to the high productivity BSGB. Together, they provide good proxies for studying the past BSGB variations in the Bering Sea.