Fig 1.
Geographical location of the Paulina tidal flat (Westerschelde estuary, SW Netherlands) and sampling design.
For both estuarine sediments types (HBM and LBM) triplicate samples were taken as close as technical constraints allowed. Additional cores for measuring physico-chemical parameters were taken in immediate vicinity of the sample cores (not shown on figure).
Table 1.
Physico-chemical parameters of both estuarine sediments (HBM and LBM) (n = 3).
Table 2.
Overview of 16S rRNA (n = 2), nirK (n = 3) and nirS (n = 3) gene sequences derived from HBM and LBM estuarine sediments.
Fig 2.
Distribution of 16S rRNA gene OTUs.
A-C, Venn diagrams representing the number of observed OTUs for the 16S rRNA gene. Comparisons are shown between (A) HBM replicates, (B) LBM replicates, (C) HBM (n = 2) and LBM (n = 2) samples. The number and percentage of unique and shared OTUs are given. D, The relative abundance of abundant 16S rRNA derived OTUs, grouped per phylum, from HBM (n = 2) and LBM (n = 2) sediment samples. Sequences were assigned to OTUs using sequence dissimilarity treshold of 3%. All OTUs with a relative abundance below 1% were grouped. Uncl. stands for unclassified.
Table 3.
Dissimilarity in community membership (Jaccard) and structure (Bray-Curtis) between both estuarine sediment types (HBM and LBM) based on 16S rRNA, nirK and nirS genes.
Fig 3.
Overview of diatom-associated bacteria found in different phyla.
The inner tier represents diatom-associated bacterial taxa reported by Amin et al. (35). The outer tier depicts diatom-associated bacterial taxa found in our study, either previously reported (blue) or representing potentially new diatom- bacteria associations (red). The highest taxonomic identification of these taxa is shown. Diatom-bacteria associations were identified based on the difference in relative abundances of specific taxa (i.e. number of sequences per taxon) between HBM and LBM sediment samples.
Table 4.
Detection and distribution of bacterial phyla (or subdivisions of Proteobacteria).
Fig 4.
Venn diagrams representing number of observed OTUs for the nirK (A) and nirS (B) genes.
Comparison is shown between HBM and LBM samples (n = 3) for both genes. The number and percentage of unique and shared OTUs are given.
Table 5.
Absolute and relative quantification of 16S rRNA, nirK and nirS genes in both estuarine sediment types (HBM and LBM).