Abstract
High-resolution 16S rRNA tag pyrosequencing was used to obtain seasonal snapshots of the bacterial diversity and community structure at two locations in Gosung Bay (South Sea, Korea) over a one year period. Seasonal sampling from the water column at each site revealed highly diverse bacterial communities containing up to 900 estimated Operational Taxonomic Units (OTUs). The Alphaproteobacteria and Gammaproteobacteria were the most abundant groups, and the most frequently recorded OTUs were members of Pelagibacter and Glaciecola. In particular, it was observed that Arcobacter, a genus of the Epsilonproteobacteria, dominated during summer. In addition, Psedoalteromonadaceae, Vibrionaceae and SAR11-1 were predominant members of the OTUs found in all sampling seasons. Environmental factors significantly influenced the bacterial community structure among season, with the phosphate and nitrate concentrations contributing strongly to the spatial distribution of the Alphaproteobacteria; the Gammaproteobacteria, Flavobacteria, and Actinobacteria all showed marked negative correlations with all measured nutrients, particularly silicon dioxide and chlorophyll-a. The results suggest that seasonal changes in environmental variables contribute to the dynamic structure of the bacterial community in the study area.
Highlights
Knowledge of the distribution and abundance of bacteria and the environmental factors that control them is crucial for understanding and predicting ecosystem function and the responses to of future changes of the ecosystem [1, 2]
To determine the composition and distribution of bacteria in the water column, seasonal samples were collected at two sites in Gosung Bay (Fig 1); environmental factors including temperature, dissolved oxygen (DO), chlorophyll-a and various nutrients differed significantly among the seasons (Table 1)
On the basis of the nonparametric Chao1 index, the richness of the entire bacterial community was highest during spring, while the bacterial diversity appeared to be similar between the sampling sites and among seasons, based on the Shannon diversity index; the exception was the spring water column, which showed much more bacterial diversity than in the other seasons
Summary
Knowledge of the distribution and abundance of bacteria and the environmental factors that control them is crucial for understanding and predicting ecosystem function and the responses to of future changes of the ecosystem [1, 2]. High-throughput pyrosequencing techniques for phylogenetically informative marker genes, including the ribosomal RNA (rRNA) genes, have recently provided evidence that marine bacteria may exhibit spatial patterns akin to those of larger organisms, in terms of distribution and abundance, but their temporal patterns remain relatively unexplored in the ocean water column [9,10,11,12]; the finding obtained far have led to comprehensive descriptions of natural microbial assemblages [13, 14]. Investigations of the temporal trends of various bacterial groups over multiple years have indicated that certain groups tend to be more common during particular seasons, showing statistically robust and predictable patterns in microbial communities [17, 18]
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