Microbial diversity and community structure across environmental gradients in Bransfield Strait, Western Antarctic Peninsula

Abstract

These authors have contributed equally to this work.The Southern Ocean is currently subject to intense investigations, mainly related to its importance for global biogeochemical cycles and its alarming rate of warming in response to climate change. Microbes play an essential role in the functioning of this ecosystem and are the main drivers of the biogeochemical cycling of elements. Yet, the diversity and abundance of microorganisms in this system remain poorly studied, in particular with regards to changes along environmental gradients. Here, we used amplicon sequencing of 16S rRNA gene tags using primers covering both Bacteria and Archaea to assess the composition and diversity of the microbial communities from four sampling depths (surface, the maximum and minimum of the oxygen concentration, and near the seafloor) at 10 oceanographic stations located in Bransfield Strait [northwest of the Antarctic Peninsula (AP)] and near the sea ice edge (north of the AP). Samples collected near the seafloor and at the oxygen minimum exhibited a higher diversity than those from the surface and oxygen maximum for both bacterial and archaeal communities. The main taxonomic groups identified below 100 m were Thaumarchaeota, Euryarchaeota and Proteobacteria (Gamma-, Delta-, Beta-, and Alphaproteobacteria), whereas in the mixed layer above 100 m Bacteroidetes and Proteobacteria (mainly Alpha-and Gammaproteobacteria) were found to be dominant. A combination of environmental factors seems to influence the microbial community composition. Our results help to understand how the dynamic seascape of the Southern Ocean shapes the microbial community composition and set a baseline for upcoming studies to evaluate the response of this ecosystem to future changes.

Linking Seasonal Reduction of Microbial Diversity to Increase in Winter Temperature of Waters of a Chilean Patagonia Fjord

“…Our observations are consistent with reports showing predominance of the same taxa of bacteria in large brackish environments (Riemann et al, 2008), in estuaries and coastal saline gradients (Campbell et al, 2011;Herlemann et al, 2011;Fortunato et al, 2012;Fortunato and Crump, 2015), and in polar surface waters (Zeng et al, 2009;Teske et al, 2011;Prasad et al, 2014;Signori et al, 2014;Piquet et al, 2015) and Patagonian glacial fjords (Gutiérrez et al, 2015). For archaeal OTUs, predominance of members of the phylum Thaumarchaeota (including Marine group I Archaea) is consistent with this group being a major contributor to microbial diversity in estuarine waters and sediments (Webster et al, 2015;Xia et al, 2015), in polar waters (Bano et al, 2004;Galand et al, 2008Galand et al, , 2009a, in sea ice (Collins et al, 2010;Cowie et al, 2011) and in fjord environments (Zaikova et al, 2010;Gutiérrez et al, 2015).…”

“…Salinity and oxygen concentration exerted major controls on prokaryotic community composition among the contrasting water masses identified during the present study in Puyuhuapi Fjord (Figure 4). Salinity is known to be a major factor influencing global biogeography of microorganisms (Lozupone and Knight, 2007;Auguet et al, 2012) and the spatial variability of microbial communities along coastal ecotones (Herlemann et al, 2011;Campbell and Kirchman, 2013;Fortunato and Crump, 2015), including polar and fjord waters (Signori et al, 2014;Gutiérrez et al, 2015). Dissolved oxygen is also known to have a major influence on microbial diversity and activity in marine environments exhibiting strong vertical oxygen gradients (Stevens and Ulloa, 2008;Wright et al, 2012).…”

Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

“…Bacterioplankton (free-floating and particle-attached archaea and bacteria) community dynamics are closely coupled to phytoplankton dynamics in the upper ocean, and strongly influenced by environmental characteristics, such as sea ice, salinity, temperature, stratification and nutrient availability (e.g. Ghiglione and Murray 2012;Luria et al 2016Luria et al , 2017Piquet et al 2011;Rozema et al 2017b;Signori et al 2014;Obryk et al 2016). These microbial communities play a key role in biogeochemical cycling.…”

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria

“…DNA was extracted as previously described (Signori et al, 2014). Briefly, filter pieces containing cells were lysed in a NaCl-sucrose buffer with lysozyme, SDS and proteinase K, and DNA was subsequently precipitated with sodium acetate/ethanol and linear acrylamide as a co-precipitant due to low concentrations of DNA present.…”