Table_1_Effects of Ice-Algal Aggregate Export on the Connectivity of Bacterial Communities in the Central Arctic Ocean.XLSX

In summer 2012, Arctic sea ice declined to a record minimum and, as a consequence of the melting, large amounts of aggregated ice-algae sank to the seafloor at more than 4,000 m depth. In this study, we assessed the composition, turnover and connectivity of bacterial and microbial eukaryotic communities across Arctic habitats from sea ice, algal aggregates and surface waters to the seafloor. Eukaryotic communities were dominated by diatoms, dinoflagellates and other alveolates in all samples, and showed highest richness and diversity in sea-ice habitats (∼400–500 OTUs). Flavobacteriia and Gammaproteobacteria were the predominant bacterial classes across all investigated Arctic habitats. Bacterial community richness and diversity peaked in deep-sea samples (∼1,700 OTUs). Algal aggregate-associated bacterial communities were mainly recruited from the sea-ice community, and were transported to the seafloor with the sinking ice algae. The algal deposits at the seafloor had a unique community structure, with some shared sequences with both the original sea-ice community (22% OTU overlap), as well as with the deep-sea sediment community (17% OTU overlap). We conclude that ice-algal aggregate export does not only affect carbon export from the surface to the seafloor, but may change microbial community composition in central Arctic habitats with potential effects for benthic ecosystem functioning in the future.

2012年夏季，北极海冰缩减至有记录以来的最低值，受海冰消融影响，大量聚集的冰藻沉降至4000余米深的海底。本研究针对北极各类生境——从海冰、藻聚集体、表层海水至海底——中的细菌与微生物真核生物群落，评估了其组成、周转特征与群落连通性。所有样本中的真核生物群落均以硅藻、甲藻及其他囊泡虫类为优势类群，且在海冰生境中展现出最高的丰富度与多样性，约含400~500个操作分类单元（Operational Taxonomic Unit，OTU）。在所有调查的北极生境中，黄杆菌纲（Flavobacteriia）与γ-变形菌纲（Gammaproteobacteria）为主要的细菌类群；细菌群落的丰富度与多样性在深海样本中达到峰值，约含1700个OTU。与藻聚集体相关的细菌群落主要由海冰群落招募获得，并随沉降的冰藻被运输至海底。海底的藻沉积物拥有独特的群落结构，其部分序列既与原始海冰群落存在22%的OTU重叠率，也与深海沉积物群落存在17%的OTU重叠率。本研究表明，冰藻聚集体的输出不仅会影响表层海洋至海底的碳输出通量，还可能改变北极中部生境的微生物群落组成，进而对未来的底栖生态系统功能产生潜在影响。