Effects of varying food-availability on ecology and distribution of smallest benthic organisms in sediments of the arctic Fram Strait during POLARSTERN cruise ARK-XV/2

With the aims of investigating the response of the smallest benthic biota to a strong ice-edge-related input of phytodetritus, and of registering supposed lateral transportation processes of phytodetrital matter with northerly direction under the ice, we analysed a number of abiotic and biotic parameters in surface sediments from the northern Fram Strait. Two transects of 14 stations in total were made. One transect, crossing the Fram Strait from the east to the west, followed mainly the ice edge. The second transect extended latitudinally in a northerly direction, starting in ice-free areas, passing the ice edge, and ending in heavy ice-covered areas, approximately 100 nm north of the ice edge. Stations along this transect were sampled at almost constant water depths to avoid depth-related influences in our investigations. Results showed the expected high phytodetritus concentrations in the ice-edge vicinity. Concentrations of sediment-bound plant pigments were approximately 5 times higher than in ice-covered areas, indicating a very strong phytodetritus input. With increasing distance from the highly productive areas at the ice edge, we found significantly decreasing concentrations of phytodetrital input to the seafloor in a northerly direction. Within the foraminiferans, generic diversity was clearly reduced in the area of strong phytodetritus deposition. Along the latitudinal transect, out of the direct ice-edge influence, foraminiferal diversities slowly increased within increasing distance from the ice edge. The integration of results from earlier foraminiferal investigations, from stations further to the north, indicates a once more decreasing diversity with continually decreasing food supply.

本研究旨在探究小型底栖生物（benthic biota）对冰缘相关强植物碎屑（phytodetritus）输入的响应，并记录冰下植物碎屑物质向北的推测性侧向输运过程，为此我们对弗拉姆海峡（Fram Strait）北部表层沉积物中的多项非生物与生物参数展开了分析。
本次研究共布设两条断面，总计14个采样站位。第一条断面自东向西横穿弗拉姆海峡，基本沿冰缘布设。第二条断面沿纬度方向向北延伸，起点为无冰海域，途经冰缘区域，终点位于冰缘以北约100海里的重冰覆盖海域。为规避水深对本研究的干扰，该断面上的所有站位均采用近似恒定的水深开展采样。
研究结果显示，冰缘附近区域的植物碎屑浓度正如预期般处于较高水平。沉积物结合态植物色素的浓度约为冰覆盖海域的5倍，表明此处存在极强的植物碎屑输入。随着与冰缘高生产力区域的距离增加，向北方向的海底植物碎屑输入浓度呈现显著下降趋势。在有孔虫类（foraminiferans）中，强植物碎屑沉积区域的属多样性明显降低。沿纬度断面，在脱离冰缘直接影响的区域内，有孔虫属多样性随着与冰缘距离的增加而缓慢升高。结合此前针对更北部站位的有孔虫研究结果可知，随着食物供给持续减少，有孔虫多样性会再次出现下降。