|Title||Vertically distinct microbial communities in the Mariana and Kermadec trenches|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Peoples L.M, Donaldson S., Osuntokun O., Xia Q., Nelson A., Blanton J., Allen EE, Church M.J, Bartlett DH|
|Type of Article||Article|
|Keywords||bacterioplankton; Challenger Deep; deep-sea; Distribution; hadal trenches; hydrostatic-pressure; japan trench; organic-matter; pacific-ocean; phylogenetic analysis; Science & Technology - Other Topics; sp-nov.|
Hadal trenches, oceanic locations deeper than 6,000 m, are thought to have distinct microbial communities compared to those at shallower depths due to high hydrostatic pressures, topographical funneling of organic matter, and biogeographical isolation. Here we evaluate the hypothesis that hadal trenches contain unique microbial biodiversity through analyses of the communities present in the bottom waters of the Kermadec and Mariana trenches. Estimates of microbial protein production indicate active populations under in situ hydrostatic pressures and increasing adaptation to pressure with depth. Depth, trench of collection, and size fraction are important drivers of microbial community structure. Many putative hadal bathytypes, such as members related to the Marinimicrobia, Rhodobacteraceae, Rhodospirilliceae, and Aquibacter, are similar to members identified in other trenches. Most of the differences between the two trench microbiomes consists of taxa belonging to the Gammaproteobacteria whose distributions extend throughout the water column. Growth and survival estimates of representative isolates of these taxa under deep-sea conditions suggest that some members may descend from shallower depths and exist as a potentially inactive fraction of the hadal zone. We conclude that the distinct pelagic communities residing in these two trenches, and perhaps by extension other trenches, reflect both cosmopolitan hadal bathytypes and ubiquitous genera found throughout the water column.
Hadal microbial communities have been proposed to contain distinct taxa adapted to the unique in situ conditions found in trenches. Here, we show that hadal communities within the Kermadec and Mariana trenches are indeed distinct from the abyssal assemblages above them. Hadal communities are enriched in certain taxa that may represent bathytypes, including clades such as the Marinimicrobia and specific genera such as Aquibacter. Sequences related to known piezophiles were identified in both trenches, albeit in higher abundances in the Kermadec Trench, but at <1% of total communities. These findings suggest similar hadal-associated taxa are present in multiple trenches, potentially transported by deep-ocean currents. Such lineages may be responsible for the higher rates of activity under in situ rather than atmospheric pressures determined here. Communities were also distinct between the Mariana and Kermadec trenches, showing varying abundances of cosmopolitan taxa and the presence of unique but rare OTUs. Inter-trench variation was largely driven by differentially abundant heterotrophic Gammaproteobacteria that show a remarkable ability to survive long-term pressurization and may be from bathyal and shallower depths where they colonize particles and sink. Trenches are therefore home to unique microbial communities, comprised of autochthonous, pressure-adapted members and ubiquitous genera found throughout the water column.