Abstract
Particle-attached (PA) and free-living (FL) microorganisms play significant but different roles in mineralization of organic matter (OM) in the ocean. Currently, little is known about PA and FL microbial communities in bathyal and abyssal pelagic waters, and understanding of their diversity and distribution in the water column and their interactions with environmental factors in the trench area is limited. We investigated for the first time the variations of abundance and diversities of the PA and FL bacterial communities in the epi-, bathy-, and abyssopelagic zones of the New Britain Trench (NBT). The PA communities showed decreasing species richness but increasing relative abundance with depth, suggesting the increasing ecological significance of the PA bacteria in the deep ocean. The abundance and diversity of PA and FL bacterial communities in the NBT water column appeared to be shaped by different sets of environment factors, which might be related to different micro-niches of the two communities. Analysis on species distribution suggested that the differences between PA and FL bacteria communities mainly resulted from the different relative abundance of the “shared taxa” in the two types of communities. These findings provide valuable information for understanding the relative ecological roles of the PA and FL bacterial communities and their interactions with environmental factors in different pelagic zones along the vertical profile of the NBT water column.
Highlights
The pelagic deep ocean contains 70% of the ocean’s microbial cells and 60% of its heterotrophic activity, playing a significant role in regulating the biogeochemical cycles of the earth (Arístegui et al, 2009)
We investigate for the first time the changes of abundance and diversity of the PA and FL bacterial communities in the water column of the New Britain Trench (NBT)
We investigated for the first time the vertical variations of abundance and diversity of PA and FL bacterial communities from surface ocean to abyssopelagic waters in the New Britain Trench
Summary
The pelagic deep ocean contains 70% of the ocean’s microbial cells and 60% of its heterotrophic activity, playing a significant role in regulating the biogeochemical cycles of the earth (Arístegui et al, 2009). The PA and FL communities have been reported to harbor different groups of microbial lineages in various marine environments including coastal or surface water (Mohit et al, 2014; Zhang et al, 2016), bathypelagic water (Wilkins et al, 2013; Salazar et al, 2016; Milici et al, 2017) or even extreme depths of hadalpelagic habitats (>6000 m) (Eloe et al, 2011b; Tarn et al, 2016) These studies mainly focus on the shallower waters or a particular depth in the deep ocean, and understanding on variations of PA and FL communities along the vertical profile is limited (Li et al, 2015; Milici et al, 2017). It is not clear whether the two microbial communities respond differently to the changes of environmental conditions along vertical scale from surface to abyssopelagic depths, and if so, what are the major factors controlling the vertical variations of PA and FL communities?
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