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ORIGINAL RESEARCH article

Front. Microbiol.
Sec. Extreme Microbiology
Volume 15 - 2024 | doi: 10.3389/fmicb.2024.1420899

Metagenomic 18S rDNA reads revealed zonation of eukaryotic communities in the Yongle blue hole

Provisionally accepted
Hongxi Zhang Hongxi Zhang 1*Taoshu Wei Taoshu Wei 1Qingmei Li Qingmei Li 1Liang Fu Liang Fu 2Lisheng He Lisheng He 1Yong Wang Yong Wang 3*
  • 1 Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences (CAS), Sanya, China
  • 2 Sansha Track Ocean Coral Reef Conservation Research Institute Co., Ltd, Sansha, China
  • 3 Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, China

The final, formatted version of the article will be published soon.

    The Yongle blue hole (YBH), situated in the South China Sea, represents a compelling subject of study in marine microbiology due to its unique redox-layered microbial ecosystems. However, the diversity and ecology of microbial eukaryotes within the YBH remains underexplored. This study endeavors to bridge this gap through the application of the in situ microbial filtration and fixation (ISMIFF) device to collect 0.22-30 μm microbial samples from 21 water layers of YBH. Subsequent extraction of 18S rRNA metagenomic reads of 21 metagenomes and 10 metatranscriptomes facilitated a comprehensive analysis of community structures. Findings revealed a pronounced superiority in the diversity and richness of eukaryotic microorganisms in the oxic zone compared to its suboxic and anoxic counterparts. Notably, Dinophyceae and Maxillopoda emerged as the predominant taxa based on the analysis of the 18S rRNA reads for the V4 and V9 regions, which showed stratification in their relative abundance and suggested their potential role in the thermo-halocline boundaries and oxic-anoxic interface. Specifically, in these eukaryotic microbial communities, Dinophyceae exhibited significant abundance at 20 m (20.01%) and 105 m (26.13%) water depths, while Maxillopoda was prevalent at 40 m (22.84%), 80 m (23.19%), and 100 m (15.42%) depths. A part of these organisms, identified as larvae and protists, were likely attracted by swarming chemosynthetic bacterial prey prevailing at the thermo-halocline boundaries and oxic-anoxic interface. Furthermore, the phylogenetic relationships of the major 18S operational taxonomic units (OTUs) showed a close adjacency to known species, except for three Dinophyceae OTUs. In conclusion, this study provides critical insights into the vertical distribution and transcriptional activity of <30-μm eukaryotic microbes, shedding light on the taxonomic novelty of eukaryotic microorganisms within the semi-enclosed blue holes.

    Keywords: Yongle blue hole, 18S rRNA gene, eukaryotic communities, Anoxic water, Metagenomics

    Received: 21 Apr 2024; Accepted: 15 Jul 2024.

    Copyright: © 2024 Zhang, Wei, Li, Fu, He and Wang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence:
    Hongxi Zhang, Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences (CAS), Sanya, China
    Yong Wang, Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, China

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