Distribution of Recent benthic foraminifera in Arctic galciomarine sediments

Foraminifera were examined in recent (<100 years) fine-grained glaciomarine muds from surface sediments and cores from Nordensheld Bay, Novaja Zemlja, and Hornsund and Bellsund, Spitsbergen. This study presents the first data on modern foraminifera distribution for fjord environments in Novaja Zemlja, Russia. The data are interpreted with reference to the distribution of foraminiferal near Svalbard and the Barents Sea. In Nordensheld Bay, live and dead Nonionellina labradorica and Islandiella norcrossi are most abundant in the outer fjord. Cassidulina reniforme and Allogromiina spp. dominate in the middle and inner fjord. The dominant species are dissimilar to species occurring in other areas of the Barents Sea region, with the exception of Svalbard fjords. The number of live foraminifera (24 to 122 tests/10 cm1) in outer and middle Nordensheld Bay corresponds with values known from the open Barents Sea. However, the biomass (0.03 mg/10 cm**3) is two orders of magnitude less due to smaller foraminiferal test size, which in glaciomarine sediments reflects the absence of larger species, paucity of large specimens, and high occurrence of juvenile foraminifera. The smaller size indicates an opportunistic response to environmental stress due to glacier proximity. The presence of Quinqueloculina stalkeri is diagnostic of glaciomarine environments in fjords of Novaja Zemlja and Svalbard.本次研究针对取自俄罗斯新地岛诺登舍尔德湾、斯匹次卑尔根霍恩松德湾与贝尔松德湾的表层沉积物及岩心中的近百年（<100年）细粒冰海相泥质沉积物内的有孔虫（Foraminifera）开展了镜检分析。本研究首次提供了俄罗斯新地岛峡湾环境中现代有孔虫的分布数据。本次所得数据结合斯瓦尔巴群岛及巴伦支海周边的有孔虫分布情况进行了解释。在诺登舍尔德湾中，活壳体与死壳体的拉布拉多拟九字虫（Nonionellina labradorica）及诺氏岛球虫（Islandiella norcrossi）在峡湾外带丰度最高；肾形鸭咀虫（Cassidulina reniforme）与拟编织虫属（Allogromiina spp.）则在峡湾中带与内带占据优势。该区域的优势有孔虫物种与巴伦支海其他区域的物种组成存在显著差异，仅斯瓦尔巴群岛峡湾除外。诺登舍尔德湾外带与中带的活有孔虫丰度（24~122个壳体/10 cm³）与开阔巴伦支海的已知数据基本一致，但生物量（0.03 mg/10 cm³）却比前者低两个数量级，这源于有孔虫壳体尺寸偏小。冰海相沉积物中的小型壳体反映出区域内缺乏大型有孔虫物种、大型个体稀少且幼体占比偏高。壳体尺寸偏小表明有孔虫对冰川邻近带来的环境压力采取了机会主义生存策略。斯氏五玦虫（Quinqueloculina stalkeri）的存在可作为新地岛与斯瓦尔巴群岛峡湾冰海相环境的诊断性标志。