Abstract
Despite numerous studies on marine prokaryotes, the vertical distribution patterns of bacterial community, either on the taxonomic composition or the functional structure, remains relatively unexplored. Using HiSeq-derived 16S rRNA data, the depth-related distribution patterns of taxonomic diversity and functional structure predicted from diversity data in the water column and sediments of the Western Pacific Ocean were explored. The OTU richness declined along the water column after peaking between 100 to 200 m deep. Relative abundance of Cyanobacteria and SAR11 decreased significantly with depth, while Actinobacteria and Gammaproteobacteria increased. This clearly mirrors the vertical distribution pattern of the predicted functional composition with the shift between phototrophic to chemoheterotrophic groups from the surface to the deeper layers. In terms of community composition and functional structure, the epipelagic zone differed from other deeper ones (i.e., meso-, bathy-, and abyssopelagic zones) where no obvious differences were detected. For the epipelagic zone, temperature, dissolved oxygen, and salinity were recognized as the crucial factors shaping both community composition and the functional structure of bacteria. Compared with water samples, benthic sediment samples harbored unexpectedly higher read abundance of Proteobacteria, presenting distinguishable taxonomic and functional compositions. This study provides novel knowledge on the vertical distribution of bacterial taxonomic and functional compositions in the western Pacific.
Highlights
Bacterioplankton are considered to play a central role in the biological cycle of carbon through the microbial loop (Stocker, 2012; Fuhrman et al, 2015)
Water samples were collected from the surface to the near bottom of seven stations at 11–15 different depths according to water depth (Supplementary Table S1) using 25 L Niskin bottles mounted on a Seabird conductivity temperature depth probe (CTD) rosette
Bacterial diversity was significantly higher in the epipelagic zone than in the deeper zones in terms of OTU richness (p < 0.05)
Summary
Bacterioplankton are considered to play a central role in the biological cycle of carbon through the microbial loop (Stocker, 2012; Fuhrman et al, 2015). Previous studies indicated that bacterial richness and communities on the surface of water columns in the ocean vary from those in deeper levels (Delong et al, 2006; Durbin and Teske, 2011; Tseng et al, 2015; Zorz et al, 2019), as well as from those in seafloor sediments (Bienhold et al, 2016; Walsh et al, 2016). Vertical Distribution of Bacterial Communities in water samples from the Pacific, whereas the aphoticzone samples (below the DCM) were mainly dominated by Alpha-, Gamma-, Deltaproteobacteria, and Deferribacteres. More information on this topic, from various marine habitats, would be a valuable piece of the puzzle
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