Distribution and Niche Separation of Planktonic Microbial Communities in the Water Columns from the Surface to the Hadal Waters of the Japan Trench under the Eutrophic Ocean

Abstract

The Japan Trench is located under the eutrophic Northwestern Pacific while the Mariana Trench that harbors the unique hadal planktonic biosphere is located under the oligotrophic Pacific. Water samples from the sea surface to just above the seafloor at a total of 11 stations including a trench axis station, were investigated several months after the Tohoku Earthquake in March 2011. High turbidity zones in deep waters were observed at most of the sampling stations. The small subunit (SSU) rRNA gene community structures in the hadal waters (water depths below 6000 m) at the trench axis station were distinct from those in the overlying meso-, bathy and abyssopelagic waters (water depths between 200 and 1000 m, 1000 and 4000 m, and 4000 and 6000 m, respectively), although the SSU rRNA gene sequences suggested that potential heterotrophic bacteria dominated in all of the waters. Potential niche separation of nitrifiers, including ammonia-oxidizing archaea (AOA), was revealed by quantitative PCR analyses. It seems likely that Nitrosopumilus-like AOAs respond to a high flux of electron donors and dominate in several zones of water columns including shallow and very deep waters. This study highlights the effects of suspended organic matter, as induced by seafloor deformation, on microbial communities in deep waters and confirm the occurrence of the distinctive hadal biosphere in global trench environments hypothesized in the previous study.

In situ meta‐omic insights into the community compositions and ecological roles of hadal microbes in the Mariana Trench

“…Relative abundance of microbial taxa in the hadal samples based on 16S rRNA gene amplicons was summarized Table 4). Our profile data of hadal microbial communities were compared with those of the samples collected using Niskin bottles from the surface water to the deepest region of the Mariana Trench in the previous work (Nunoura et al, 2015). Microbial communities of the in situ hadal samples were obviously distinct from those of the Niskin samples ( Supplementary Fig.…”

“…Compositions of microbial assemblages in the Puerto Rico Trench (PRT) from 6000 m depth were the first hadal microbial communities reported using the improved sequencing techniques (Eloe et al, 2011a). The following work exhibited a vertical profile of planktonic microbial communities from surface water to the deepest region of the Mariana Trench, in which heterotrophic microbial lineages were more abundant in the hadal waters compared to the upper abyssal oceans and potentially represented distinct microbial ecosystem driven by endogenous recycling of organic matter (Nunoura et al, 2015). Dominant species in hadal freeliving and particle-associated microbial communities were then uncovered, which highlighted the potential importance of heterotrophy, sulfur-cycling, and methane and hydrogen utilization within the hadal bottom waters of the Mariana Trench (Tarn et al, 2016).…”

“…5A). Ammonia source in ocean ecosystem was probably derived from nitrogenous organic matter decomposition (Nunoura et al, 2015). Interestingly, three groups of MAGs separately have the genes encoding nitronate monooxygenase for nitroalkane oxidization (B7, P11, P20, P21, EN27 and CH23), genes encoding nitrilase for hydrolyzing nitrile hydrolyzation (B7, EN26, T3 and T4) and genes encoding formamidase for formamide hydrolyzation (P10, CH6, CH23 and CH29).…”

“…Dominant species in hadal free‐living and particle‐associated microbial communities were then uncovered, which highlighted the potential importance of heterotrophy, sulfur‐cycling, and methane and hydrogen utilization within the hadal bottom waters of the Mariana Trench (Tarn et al ., ). The most recent comparative analysis of microbial communities in different trenches further indicated the occurrence of distinctive hadal biospheres in global trench environments (Nunoura et al ., ; Liu et al ., ; Peoples et al ., ).…”

“…Since then, hundreds of new microbial strains were isolated from hadal trenches and the composition of hadal microbial communities was also casually determined using culturing and/or conventional 16S rRNA gene cloning methods (Bartlett, 2009;Cao et al, 2014). Only recently, nextgeneration sequencing techniques facilitated the studies on hadal microbial communities and provided in-depth insight on them (Eloe et al, 2011a;Nunoura et al, 2015Nunoura et al, , 2016Tarn et al, 2016;Liu et al, 2018;Peoples et al, 2018;Wang et al, 2019a). Compositions of microbial assemblages in the Puerto Rico Trench (PRT) from 6000 m depth were the first hadal microbial communities reported using the improved sequencing techniques (Eloe et al, 2011a).…”