PUB - Publikationen an der Universität Bielefeld

The South Pacific Gyre (SPG) covers 10% of the ocean's surface and is often regarded as a marine biological desert. To gain an on-site overview of the remote, ultra-oligotrophic microbial community of the SPG we developed a novel on-board analysis pipeline, which combines next-generation sequencing with fluorescence in situ hybridisation and automated cell enumeration. We tested the pipeline during the SO245 "UltraPac" cruise from Chile to New Zealand and found that the overall microbial community of the SPG was highly similar to that of other oceanic gyres. The SPG was dominated by 20 major bacterial clades, including SAR11, SAR116, AEGEAN-169 marine group, SAR86, Prochlorococcus, SAR324, SAR406, and SAR202. Most of the bacterial clades showed a strong vertical (20 m - 5000 m), but only a weak longitudinal (80°W - 160°W), distribution pattern. Surprisingly, in the central gyre Prochlorococcus, the dominant photosynthetic organism, had only low cellular abundances in the upper waters (20 - 80 m) and were more frequent around the 1% irradiance zone (100 - 150 m). Instead, the surface waters of the central gyre were dominated by SAR11, SAR86, and SAR116 clades known to harbour light-driven proton pumps. The alphaproteobacterial AEGEAN-169 marine-group was particularly abundant in the surface waters of the central gyre indicating a potentially interesting adaptation to ultraoligotrophic waters and high solar irradiance. In the future, the newly developed community analysis pipeline will allow for on-site insights into a microbial community within 35 hours of sampling, which will permit more targeted sampling efforts and hypothesis-driven research.ImportanceThe South Pacific Gyre is due to its vast size and remoteness one of the least studied oceanic regions on earth. However, both remote sensing and in situ measurements indicated that the activity of its microbial community contributes significantly to global biogeochemical cycles. Presented here is an unparalleled investigation of the microbial community of the SPG from 20 - 5000 m depth covering a geographic distance of 7000 km. This insight was achieved through the development of a novel on-board analysis pipeline, which combines next-generation sequencing with fluorescence in situ hybridisation and automated cell enumeration. The pipeline is well comparable to on-shore systems based on the Illumina platforms and yields microbial community data in less than 35 hours after sampling. Going forward the ability to gain on-site knowledge of a remote microbial community will permit hypothesis-driven research, through the generation of novel scientific questions and subsequent additional targeted sampling efforts. Copyright © 2019 American Society for Microbiology.