Diversity of Pelagic and Benthic Bacterial Assemblages in the Western Pacific Ocean

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.

Biodiversity and Biogeography of Abundant and Rare Microbial Assemblages in the Western Subtropical Pacific Ocean

“…In the open sea, past investigations on abundant and rare microbial taxa have mainly focused on coastal oceans ( Campbell et al, 2011 ; Mo et al, 2018 ), the Mediterranean Sea ( Hugoni et al, 2013 ; Baltar et al, 2015 ), and the Arctic Ocean ( Galand et al, 2009 ). The western Pacific Ocean has not received much research attention, so our knowledge of pelagic microbial biodiversity and biogeography in this area is still rather limited ( Wang et al, 2020 ). Recently, Liang et al (2017) used a flow cytometer to determine the abundances and distributions of picoplankton and virioplankton in the epi-, meso-, and bathypelagic zones of the western Pacific Ocean.…”

“…Recently, Liang et al (2017) used a flow cytometer to determine the abundances and distributions of picoplankton and virioplankton in the epi-, meso-, and bathypelagic zones of the western Pacific Ocean. With the development of high-throughput sequencing, the diversity and functional structure of pelagic and benthic bacterial assemblages in the western Pacific Ocean were further estimated ( Wang et al, 2020 ), because this technique can help researchers to better identify variation in less abundant species and picoplankton populations when compared with traditional methods. A few studies have analyzed the active planktonic marine archaeal community from the deep chlorophyll maximum (DCM) of the western Pacific Ocean ( Dai et al, 2020 ).…”

“…One is a niche-based (environmental selection-related) process ( Vellend, 2010 ) and the other is neutral (dispersal-related) process ( Caswell, 1976 ; Hubbell, 2001 ). In the western Pacific Ocean, previous studies have shown that environmental factors [e.g., dissolved oxygen (DO), temperature, and salinity] were significantly correlated with microbial community composition and the functional structure of bacterial communities in the epipelagic zone ( Wang et al, 2020 ). Meanwhile, the neutral processes that explain the nature of microbial communities in the western Pacific Ocean have seldom been evaluated.…”

Sargasso Sea bacterioplankton community structure and drivers of variance as revealed by DNA metabarcoding analysis

“…Bacterial species richness was greater in the DCM than at the surface, with this difference being most pronounced in the South Sargasso Sea. Previous studies have found that bacterial richness increases with depth through the water column up to the 0.1% light level ( Treusch et al, 2009 ), peaking near the bottom of the epipelagic and gradually declining with increased depth ( Wang et al, 2020 ). The trend of increasing diversity with depth is often amplified in oceanic regions such as the Sargasso Sea with significant stratification and oligotrophic surface conditions ( Gajigan et al, 2018 ; West et al, 2016 ), where surface waters are heavily impacted by rainfall, sun exposure, flotsam, and other conditions that may permit more dynamic fluctuations of opportunistic bacterial taxa.…”

“…One study focusing on widely distributed marine microbes such as SAR11 and Actinobacteria, which we found to be dominant in Sargasso Sea communities, indicated that temperature significantly influences community dissimilarity, even when environmental differences associated with distance are eliminated ( West et al, 2016 ). Further, seasonal mixing events and productivity cycles created by shifts in temperature regimes have also been shown to impact bacterial diversity ( Wang et al, 2020 ).…”