RNA and DNA based biodiversity of sea ice protists over the central Arctic Ocean

Sea ice is a large ecosystem contributing significantly to Polar primary productivity. Especially in the northern hemisphere sea ice consists of often several meters thick multi-year ice (MYI) and thinner first-year ice (FYI). Current global warming is most severe in Arctic regions and as a consequence sea ice cover, especially for MYI is decreasing. Despite its apparent hostile nature sea ice interior is inhabited by a microbial community of bacteria and protists, many of which are photosynthetic. The composition of these communities is yet not known in detail and the relation between active cells versus those just entrapped has not been studied. Here we present data on eukaryotic biodiversity in MYI and FYI from the Central Arctic Ocean using high-throughput sequencing of 18S rRNA and rDNA amplicons. By analyzing datasets from environmental DNA versus RNA we compare the DNA-based total biodiversity to that from RNA amplicons representing the more active part of the community. We found differences between these two in that Bacillariophyceae OTUs are over-represented in the active part of the community. The important arctic diatom Melosira arctica seems to be more abundant in MYI.

海冰是一类重要的极地生态系统，对极地初级生产力贡献显著。尤其在北半球，海冰通常由数米厚的多年冰（multi-year ice, MYI）与厚度较薄的一年冰（first-year ice, FYI）组成。当前全球变暖在北极地区表现最为严重，海冰覆盖范围随之缩减，其中多年冰的减少尤为突出。尽管海冰环境看似严苛，其内部仍栖息着由细菌与原生生物构成的微生物群落，其中多数类群具备光合能力。目前学界尚未明晰这类群落的具体组成，且活性细胞与仅被包埋的细胞之间的关联尚未得到研究。本研究针对北冰洋中心区域的多年冰与一年冰，通过18S rRNA及rDNA扩增子高通量测序技术，获取了其真核生物多样性数据。通过对比环境DNA与环境RNA数据集，本研究将基于DNA检测得到的总生物多样性，与代表群落中更活跃组分的RNA扩增子结果进行了比对。研究发现两类数据集存在显著差异：硅藻门（Bacillariophyceae）的操作分类单元（operational taxonomic unit, OTU）在活性群落中占比偏高。重要的北极硅藻北极旋链藻（Melosira arctica）在多年冰中的丰度似乎更高。