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

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.

本研究对瑞典破冰船奥登（ODEN）执行的“北极海洋'96”科考航次采集的沉积物样本展开分析，首次估算了常年被冰覆盖的北极中央海域的异养活性（heterotrophic activity）与总微生物生物量（total microbial biomass，尺寸范围覆盖细菌至小型后生动物（metazoans））。研究通过分析一系列生源沉积物组分（biogenic sediment compounds，即细菌胞外酶（bacterial exoenzymes）、总腺苷酸（total adenylates）、DNA、磷脂（phospholipids）、颗粒态蛋白质（particulate proteins））来评估底栖活性（benthic activity）与生物量。相较于耗时极久的分选（sorting）、计数（enumeration）与重量测定（weight determination）方法，生化沉积物参数（biochemical sediment parameters）分析可作为一种有效手段，快速获取特定底栖系统（benthic system）的生态状况信息。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%（所有站位平均值为20%），表明沉积物样本中存在大量其他小型底内生物（infaunal organisms），极有可能包括真菌、酵母菌、鞭毛虫（flagellates）、纤毛虫（ciliates）、变形虫（amoebae）等原生动物（protozoans），以及部分小型后生动物。本研究测得的活性与生物量数值普遍极低，甚至常略低于其他深海海域的相关数据，因此北极中央海域的海底可被定义为“底栖荒漠”。尽管如此，数据仍呈现出若干清晰的趋势：例如沉积物柱（sediment column）内的数值普遍急剧下降；采样站位水深（water depth）越大，数值呈现出微弱的下降趋势；同时不同北极深海区域之间也存在差异。