Abstract
The Baltic Sea represents one of the largest brackish ecosystems where various environmental factors control dynamic seasonal shifts in the structure, diversity, and function of the planktonic microbial communities. In this study, despite seasonal fluctuations, several bacterial populations (<2% of the total OTUs) that are highly dominant (25% of relative abundance) and highly frequently occurring (>85% of occurrence) over four seasons were identified. Mathematical models using occurrence frequency and relative abundance data were able to describe community assembly persisting over time. Further, this work uncovered one of the core bacterial populations phylogenetically affiliated to SAR11 subclade IIIa. The analysis of the hypervariable region of 16S rRNA gene and single copy housekeeping genes recovered from metagenomic datasets suggested that the population was unexpectedly evolutionarily closely related to those inhabiting a mesosaline lacustrine ecosystem rather than other marine/coastal members. Our metagenomic results further revealed that the newly-identified population was the major driver facilitating the seasonal shifts in the overall community structure over the brackish waters of the Baltic Sea. The core community uncovered in this study supports the presence of a brackish water microbiome distinguishable from other marine and freshwater counterparts and will be a useful sentinel for monitoring local/global environmental changes posed on brackish surface waters.
Highlights
The Baltic Sea represents a semi-enclosed aquatic environment that receives high freshwater load but has limited connection to the ocean
Our findings provide quantitative insights into planktonic members making up the core community and help researchers focus on the key drivers, other than numerous transient organisms, shaping the community structure and function, which will be a useful basis for manipulating ecosystem services and monitoring anthropogenic environmental changes
A total of 31 metagenomic datasets originating from the same location (LMO)3 in the central area of the Baltic Sea over the four seasons (Figure S1) were first analyzed
Summary
The Baltic Sea represents a semi-enclosed aquatic environment that receives high freshwater load but has limited connection to the ocean. Earlier studies report the ubiquity and numerical dominance of SAR11 bacteria in the Baltic Sea surface waters, implying their core membership [5,6] These studies determined the abundance and occurrence of SAR11 bacteria at various taxonomic levels (e.g., from the entire SAR11 to the sub-lineage level). Since the Baltic Sea surface waters exhibit a variety of environmental conditions over the range of different spatiotemporal scales, where (e.g., a relatively narrow range of habitats/periods vs all geographical/temporal sites) the core membership of the SAR11 bacteria is valid remains to be further described. We performed a comprehensive survey of exploring core members of planktonic microbial communities in the Baltic Sea surface waters using metagenomic datasets obtained a wide range of spatial (32 locations with a greatly varied salinity from freshwater to eusaline) and temporal (over four seasons in one location) scales. Our findings provide quantitative insights into planktonic members making up the core community and help researchers focus on the key drivers, other than numerous transient organisms (satellites), shaping the community structure and function, which will be a useful basis for manipulating ecosystem services and monitoring anthropogenic environmental changes
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
