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Compositional stability of sediment microbial communities during a seagrass meadow decline

The presence of seagrass shapes surface sediments and forms a specific environment for diverse and abundant microbial communities. Although the taxonomic composition of microorganisms in seagrass meadow sediments has previously been described little is known about their response to a meadow decline. In order to assess changes in microbial communities during a declining Cymodocea nodosa meadow Illumina MiSeq sequencing of the V4 region of the 16S rRNA was performed. Sampling was carried out in surface sediments from July 2017 to October 2018 at monthly intervals. For comparison, samples from an adjacent non-vegetated area were also analyzed. Microbial communities differed primarily by sediment depth and by the presence or absence of seagrass vegetation. Although the C. nodosa meadow declined to a point where almost no leaves were present no clear temporal community variation was observed. Taxonomic analysis showed a clear dominance of bacterial over archaeal sequences with most archaeal reads classified as Nanoarchaeota, Thermoplasmatota, Crenarchaeota and Asgardarchaeota. The bacterial community was mainly composed of Desulfobacterota, Proteobacteria, Bacteroidota and Chloroflexi. Our results indicate that changing environmental conditions caused by a decline of a seagrass meadow do not have a strong effect on the microbial community composition.

seagrass meadow decline ; Cymodocea nodosa ; sediment microbial communities

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