Activity and biomass of small benthic biota in the central Arctic Ocean@en

Sediment samples collected during the expedition “Arctic Ocean '96” with the Swedish ice-breaker ODEN were investigated to estimate for the first time heterotrophic activity and total microbial biomass (size range from bacteria to small metazoans) from the perennially ice-covered central Arctic Ocean. Benthic activities and biomass were evaluated analysing a series of biogenic sediment compounds (i.e. bacterial exoenzymes, total adenylates, DNA, phospholipids, particulate proteins). In contrast to the very time-consuming sorting, enumeration and weight determination, analyses of biochemical sediment parameters may represent a useful method for obtaining rapid information on the ecological situation in a given benthic system. Bacterial cell numbers and biomass were estimated for comparison with biochemically determined biomass data, to evaluate the contribution of the bacterial biomass to the total microbial biomass. It appeared that bacterial biomass made up only 8–31% (average of all stations = 20%) of the total microbial biomass, suggesting a large fraction of other small infaunal organisms within the sediment samples (most probably fungi, yeasts, protozoans such as flagellates, ciliates or amoebae, as well as a fraction of small metazoans). Activity and biomass values determined within this study were generally extremely low, and often even slightly lower than those given for other deep oceanic regions, thus characterizing the seafloor of the central Arctic Ocean as a “benthic desert”. Nevertheless, some clear trends in the data could be found, e.g. generally sharply decreasing values within the sediment column, a vague tendency for declining values with increasing water depth of sampling stations, and also differences between various Arctic deep-sea regions.本研究针对搭乘瑞典破冰船奥登号（ODEN）开展的‘北冰洋1996’科考航次中采集的沉积物样品展开分析，首次估算了常年被冰覆盖的北极海中央区域的异养活性与总微生物生物量（涵盖从细菌到小型后生动物的尺寸范围）。研究通过分析一系列生源性沉积物组分（即细菌胞外酶、总腺苷酸、DNA、磷脂、颗粒态蛋白质），对底栖生物活性与生物量进行了评估。相较于耗时耗力的分选、计数与重量测定流程，沉积物生化参数分析可作为一种实用手段，快速获取特定底栖生态系统的生态状况相关信息。为评估细菌生物量在总微生物生物量中的占比，本研究同时估算了细菌细胞数量与生物量，并与生化测定得到的生物量数据进行对比。结果显示，细菌生物量仅占总微生物生物量的8%~31%（所有站位的平均值为20%），表明沉积物样品中存在大量其他小型底内生物类群，极有可能为真菌、酵母、各类原生动物（如鞭毛虫、纤毛虫或变形虫）以及部分小型后生动物。本研究测定的活性与生物量数值整体极低，甚至往往略低于其他深海区域的报道值，由此将北极海中央区域的海底界定为‘底栖荒漠’。不过，数据中仍存在若干明确的趋势：例如沉积物柱样内的数值普遍急剧下降；采样站位水深增加时，数值呈现微弱的下降趋势；不同北极深海区域之间也存在差异。