Hydrography shapes bacterial biogeography of the deep Arctic Ocean

Abstract

It has been long debated as to whether marine microorganisms have a ubiquitous distribution or patterns of biogeography, but recently a consensus for the existence of microbial biogeography is emerging. However, the factors controlling the distribution of marine bacteria remain poorly understood. In this study, we combine pyrosequencing and traditional Sanger sequencing of the 16S rRNA gene to describe in detail bacterial communities from the deep Arctic Ocean. We targeted three separate water masses, from three oceanic basins and show that bacteria in the Arctic Ocean have a biogeography. The biogeographical distribution of bacteria was explained by the hydrography of the Arctic Ocean and subsequent circulation of its water masses. Overall, this first taxonomic description of deep Arctic bacteria communities revealed an abundant presence of SAR11 (Alphaproteobacteria), SAR406, SAR202 (Chloroflexi) and SAR324 (Deltaproteobacteria) clusters. Within each cluster, the abundance of specific phylotypes significantly varied among water masses. Water masses probably act as physical barriers limiting the dispersal and controlling the diversity of bacteria in the ocean. Consequently, marine microbial biogeography involves more than geographical distances, as it is also dynamically associated with oceanic processes. Our ocean scale study suggests that it is essential to consider the coupling between microbial and physical oceanography to fully understand the diversity and function of marine microbes.

Ocean currents shape the microbiome of Arctic marine sediments

“…A previous study observed that water masses are a factor explaining the distribution of pelagic microbiomes in the Arctic ocean (Galand et al, 2010). Our data agree with that previous work where bacteria are concerned; however, no consistent separation by water mass was observed for archaea.…”

“…Others have observed Proteobacteria including the SAR11 and Bacteroidetes to be prominent in Arctic surface waters (Galand et al, 2010;Kirchman et al, 2010) and abundant Deltaproteobacteria in deeper waters (Galand et al, 2010). The dominance of unclassified Euryarchaeota in Beaufort Shelf waters and minimal abundance of Crenarchaeota has also been observed (Galand et al, 2006(Galand et al, , 2009.…”

“…Community composition Few previous works have explored microbial diversity in Arctic pelagic communities (Bano et al, 2004;Galand et al, 2009Galand et al, , 2010Kirchman et al, 2010) and none has examined sediment communities. Others have observed Proteobacteria including the SAR11 and Bacteroidetes to be prominent in Arctic surface waters (Galand et al, 2010;Kirchman et al, 2010) and abundant Deltaproteobacteria in deeper waters (Galand et al, 2010).…”

Mixing alters the lytic activity of viruses in the dark ocean

“…4; Appendix S1: Tables S1 and S2), although different water masses harbor different prokaryotic and virus communities (Galand et al. 2010, Agogué et al. 2011, Winter et al.…”

“…The deep ocean itself is vertically‐structured due to fine‐grained differences in temperature and salinity resulting in subtle density differences that give rise to defined water masses (Emery 2001) and harbor distinct prokaryotic and virus communities (Galand et al. 2010, Agogué et al. 2011, Winter et al.…”