Response of Arctic benthic bacterial deep-sea communities to different detritus composition during an ex-situ high pressure experiment

In a multidisciplinary ex situ experiment, benthic bacterial deep-sea communities from 2,500 m water depth at the Long-Term Ecological Research Observatory HAUSGARTEN (stationPS93/050-5 and 6), were retrieved using a TV-guided multiple corer. Surface sediments (0 - 2 cm) of 16 cores were mixed with sterile filtered deep-sea water to a final sediment dilution of 3.5 fold. The slurries were split and supplemented with five different types of habitat-related detritus: chitin, as the most abundant biopolymer in the oceans, and four different naturally occurring Arctic algae species, i.e. Thalassiosira weissflogii, Emiliania huxleyi, Bacillaria sp. and Melosira arctica. Incubations were performed in five replicates, at in situ temperature and at atmospheric pressure, as well as at in situ pressure of 250 atm. At the start of the incubation and after 23 days, changes in key community functions, i.e. extracellular enzymatic activity, oxygen respiration and secondary production of biomass (bacterial cell numbers and biomass), were assessed along with changes in the bacterial community composition based on 16S rRNA gene and 16S rRNA Illumina sequencing. In summary, differences in community structure and in the uptake and remineralization of carbon in the different treatments suggest an effect of organic matter quality on bacterial diversity as well as on carbon turnover at the seafloor.

本研究开展多学科非原位实验：从长期生态研究观测站HAUSGARTEN的2500米水深海域（站位PS93/050-5与6），采用电视引导式多管采泥器采集深海底栖细菌群落。所获16个沉积物柱样的表层沉积物（0~2 cm）与无菌过滤深海海水混合，最终沉积物稀释倍数为3.5倍。将所得沉积物悬液均分后，添加五种不同的生境相关有机碎屑：海洋中丰度最高的生物聚合物几丁质（chitin），以及四种天然北极藻类——威氏海链藻（Thalassiosira weissflogii）、赫氏圆石藻（Emiliania huxleyi）、未定种杆状硅藻（Bacillaria sp.）与北极直链藻（Melosira arctica）。实验设置5个生物学重复，分别在原位温度、常压条件以及250个标准大气压的原位压力条件下开展培养。在培养起始时刻与培养23天后，同步评估群落关键功能的变化，包括胞外酶活性、氧呼吸速率以及细菌生物量次级生产（细菌细胞数量与生物量），同时基于16S rRNA基因与16S rRNA的Illumina测序（Illumina sequencing）分析细菌群落组成的变化。综上，不同处理组的群落结构、碳摄取与碳再矿化过程存在差异，结果表明有机质质量可对海底细菌多样性以及海底碳周转过程产生影响。