Microbial diversity and biogeochemical parameters at Schulz Bank seamount (Arctic Mid-Ocean Ridge) measured in summer 2016, 2017 and 2018@en

Seamounts represent ideal systems to study the influence and interdependency of environmental gradients at a single geographic location. These topographic features represent a prominent habitat for various forms of life, including microbiota and macrobiota, spanning benthic as well as pelagic organisms. While it is known that seamounts are globally abundant structures, it still remains unclear how and to which extend the complexity of the seafloor is intertwined with the local oceanographic mosaic, biogeochemistry and microbiology of a seamount ecosystem. Along these lines, the present study aimed to explore whether and to which extend seamounts can have an imprint on the microbial community composition of seawater and of sessile benthic invertebrates, sponges. For our high-resolution sampling approach of microbial diversity (16S rRNA gene Amplicon sequencing) along with measurements of inorganic nutrients and other biogeochemical parameters, we focused on the Schulz Bank seamount ecosystem, a sponge ground ecosystem which is located on the Arctic Mid-Ocean Ridge. Seawater samples were collected at two sampling depths (mid-water: MW, and near-bed water: BW) from a total of 19 sampling sites. With a clustering approach we defined microbial micro-habitats within the pelagic realm at Schulz Bank, which were mapped onto the seamount's topography, and related to various environmental parameters (such as suspended particulate matter (SPM), dissolved inorganic carbon (DIC), silicate (SiO4−), phosphate (PO43−), ammonia (NH4+), nitrate (NO32−), nitrite (NO2), depth, and dissolved oxygen (O2)). The results of our study reveal a seamount effect (sensu stricto) on the microbial mid-water pelagic community up to approximately 200 m above the seafloor. Further, we observed a strong spatial heterogeneity in the pelagic microbial landscape across the seamount, with planktonic microbial communities reflecting oscillatory and circulatory water movements, as well as processes of bentho-pelagic coupling. Depth, NO32−, SiO4−, and O2 concentrations differed significantly between the determined pelagic microbial clusters close to the seafloor (BW), suggesting that these parameters were presumably linked to changes in microbial community structures. Secondly, we assessed the associated microbial community compositions of three sponge species along a depth gradient of the seamount. […]海山（seamount）是研究单一地理位置下环境梯度的影响及其相互依存关系的理想系统。这类地形特征是各类生命形式的重要栖息生境，涵盖底栖与浮游生物，包括微生物群落与大型生物群落。尽管已知海山在全球范围内广泛分布，但目前仍不清楚海底地貌的复杂性与海山生态系统的局地海洋水文格局、生物地球化学过程以及微生物学特征之间，究竟以何种方式、在多大程度上相互交织。基于上述研究现状，本研究旨在探索海山能否以及在多大程度上，对海水以及固着底栖无脊椎动物海绵（sponge）的微生物群落组成产生印记。针对微生物多样性的高分辨率采样（采用16S rRNA基因扩增子测序（16S rRNA gene Amplicon sequencing）技术），并同步测定无机营养盐与其他生物地球化学参数，我们将研究聚焦于北极中洋脊的舒尔茨海山（Schulz Bank）生态系统——一处海绵底栖生态系统。我们共在19个采样点的两个采样深度（中层水：MW，近底水：BW）采集了海水样本。通过聚类分析方法，我们在舒尔茨海山的浮游域内界定了微生物微生境，并将其映射至海山地貌，同时关联各类环境参数：包括悬浮颗粒物（suspended particulate matter，SPM）、溶解无机碳（dissolved inorganic carbon，DIC）、硅酸盐（SiO₄⁴⁻）、磷酸盐（PO₄³⁻）、氨（NH₄⁺）、硝酸盐（NO₃⁻，原文标注为NO32−）、亚硝酸盐（NO₂）、水深以及溶解氧（O₂）。本研究结果揭示了严格意义上的海山效应：其对海床上方约200米范围内的中层水浮游微生物群落产生影响。进一步研究发现，海山周边的浮游微生物群落景观存在显著的空间异质性，浮游微生物群落特征可反映振荡与循环水流运动以及底栖-浮游耦合过程。在靠近海床的浮游微生物聚类群（BW组）中，水深、NO₃⁻、SiO₄⁴⁻以及O₂浓度均存在显著差异，表明这些参数大概率与微生物群落结构的变化相关联。其次，我们沿海山的深度梯度评估了三种海绵物种的相关微生物群落组成。[…]