Purpose

Though the process and players of nitrification are important in the ecology and biogeochemistry of Arctic fjords; there are very limited studies available on the ecology of ammonia oxidizers. Hence, we studied the abundance, diversity, and niche separation of ammonia oxidizers in the surface sediment of two high Arctic fjords (Kongsfjorden and Krossfjorden) to explore their ecology in the Arctic system.

Materials and methods

Surface sediment samples were collected from eight stations (four stations from each fjord). The diversity and abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) were analyzed using ammonia monooxygenase A (amoA) gene from the sediment metagenome. Environmental variables including bottom temperature and salinity, and sediment characteristics such as total carbon (TC), total nitrogen (TN), total sulfur (TS), and total organic carbon (TOC), were measured.

Results and discussion

AOA were more abundant than AOB in most of the samples and AOA/AOB ratios ranged from 0.63 to 17.11. AOA were dominated by Nitrosopumilus lineage (67.5%), followed by Nitrososphaera lineage (32.2%). Most of the AOB were affiliated with Nitrosospira lineage (82.2%), and comparatively lesser contribution (18.2%) was observed for Nitrosomonas. We could not observe comammox bacteria in our samples. The distribution of ammonia oxidizers had a significant influence with the total nitrogen and total organic carbon content.

Conclusions

Both AOA and AOB showed spatial variations in community composition within the fjords and between the fjords with a domination of freshwater/soil communities in the inner fjord stations. Freshwater and soil influx from glacial melt had a significant influence in controlling the environmental variables in the fjords which in turn regulated the distribution and niche selection of ammonia oxidizers.

中文翻译：

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斯瓦尔巴特群岛北极高峡湾沉积物中独特的群落组成和氨氧化剂的丰度

目的

尽管硝化的过程和参与者在北极峡湾的生态和生物地球化学中很重要；关于氨氧化剂的生态学的研究非常有限。因此，我们研究了两个北极高峡湾（Kongsfjorden和Krossfjorden）表面沉积物中氨氧化剂的丰度，多样性和生态位分离，以探索其在北极系统中的生态。

材料和方法

从八个站点（每个峡湾四个站点）收集了地表沉积物样本。利用来自沉积物基因组的氨单氧化酶A（amoA）基因分析了氨氧化细菌（AOB）和古细菌（AOA）的多样性和丰度。测量了包括底部温度和盐度在内的环境变量，以及诸如总碳（TC），总氮（TN），总硫（TS）和总有机碳（TOC）等沉积物特征。

结果与讨论

在大多数样品中，AOA比AOB丰富，AOA / AOB的比率范围为0.63至17.11。AOA的亚种由Nitrosopumilus世系（67.5％）控制，其次是Nitrososphaera世系（32.2％）。大多数AOB与亚硝基螺菌谱系有关（82.2％），而亚硝化单胞菌的贡献相对较小（18.2％）。我们无法在样品中观察到昏迷细菌。氨氧化剂的分布对总氮和总有机碳含量有显着影响。

结论

AOA和AOB均显示峡湾内和峡湾之间的群落组成的空间变化，且峡湾内站的淡水/土壤群落占优势。冰川融化引起的淡水和土壤涌入对控制峡湾的环境变量具有重要影响，进而调节了氨氧化剂的分布和生态位选择。