Effects of Vertical Water Mass Segregation on Bacterial Community Structure in the Beaufort Sea

Abstract

The Arctic Ocean is one of the least well-studied marine microbial ecosystems. Its low-temperature and low-salinity conditions are expected to result in distinct bacterial communities, in comparison to lower latitude oceans. However, this is an ocean currently in flux, with climate change exerting pronounced effects on sea-ice coverage and freshwater inputs. How such changes will affect this ecosystem are poorly constrained. In this study, we characterized the bacterial community compositions at different depths in both coastal, freshwater-influenced, and pelagic, sea-ice-covered locations in the Beaufort Sea in the western Canadian Arctic Ocean. The environmental factors controlling the bacterial community composition and diversity were investigated. Alphaproteobacteria dominated the bacterial communities in samples from all depths and stations. The Pelagibacterales and Rhodobacterales groups were the predominant taxonomic representatives within the Alphaproteobacteria. Bacterial communities in coastal and offshore samples differed significantly, and vertical water mass segregation was the controlling factor of community composition among the offshore samples, regardless of the taxonomic level considered. These data provide an important baseline view of the bacterial community in this ocean system that will be of value for future studies investigating possible changes in the Arctic Ocean in response to global change and/or anthropogenic disturbance.

Pathway-Centric Analysis of Microbial Metabolic Potential and Expression Along Nutrient and Energy Gradients in the Western Atlantic Ocean

“…Overall, microbial communities appear to cluster into significantly distinct assemblages that can be divided into two broad marine regions: the surface (5 -150 m) and deep (250 -4000 m) ocean (Figure 3), as shown by others previously (DeLong et al, 2006;Zinger et al, 2011;Friedline et al, 2012;Milici et al, 2016a;Fu et al, 2019). Here, we observe that different microbial taxa flourish as a result of the unique conditions defining the surface, DCM, oxygen minimum and deep waters.…”

“…In the deep ocean, we observed that different indicator taxa and expressed pathways were present in the NADW compared to the bottom waters (Figures 7B, 7C and Supplementary Figures 3B, C), suggesting that these water masses have distinct microbial communities with specific metabolic processes (Shi et al, 2011;Lekunberri et al, 2013;Guerrero-Feijoo et al, 2016;Fu et al, 2019). SAR202, SAR324, and certain orders of Archaea have been found in the deep ocean below 1500 m (Vetriani et al, 1999;Morris et al, 2004;Sheik et al, 2013;Wu et al, 2013), whereas Rhodospirillales are especially common at intermediate depths (~500 m) and below 1500 m in the North Atlantic (Guerrero-Feijoo et al, 2016).…”

“…This geographical homogeneity in microbial community composition is similar to that observed elsewhere (Zinger et al, 2013;Salazar et al, 2016;Djurhuus et al, 2017;Ibarbalz et al, 2019), and is likely a result of our cruise track spanning the South Atlantic subtropical gyre and spatially expansive deep-water masses (i.e., AAIW, NADW). Gyres have been shown to facilitate the transport and mixing of microbial communities (Milici et al, 2016b), contributing to the relative uniformity observed latitudinally in microbial community distribution (Fu et al, 2019). Different deep-water masses have been shown to have characteristic temperature and salinity signatures and may serve to transport microbial communities across oceanic basins, contributing to homogenization of latitudinal differences in microbial community composition (Galand et al, 2010;Friedline et al, 2012;Pernice et al, 2016;Djurhuus et al, 2017).…”

Water mass structure determine the prokaryotic community and metabolic pattern in the Korea Strait during fall 2018 and 2019

“…In this study, we found that T and S variables have a substantial influence on all layers (Figure 4), suggesting that water mass is the primary determinant of bacterial composition. Specifically, FW has a significant impact on the physical properties of seawater, causing changes in the bacterial population (Fu et al, 2019). Compared to UL 2018, the UL 2019 (Sts.…”

“…Physical properties such as temperature (T) and salinity (S) gradients in water masses are important driving factors in determining the prokaryotic population due to their biological mediation within cells. These properties affect prokaryotic photosynthetic activity, carbon, nitrogen, and sulfur metabolism, and other functional processes in various regions including the Western Sub-Arctic (Li et al, 2018), North Atlantic (Agoguéet al, 2008), Eastern North Atlantic (Varela et al, 2008), Arctic Ocean (Galand et al, 2009), and Beaufort Sea (Fu et al, 2019). Water masses at the same location can be vertically classified into different types based on their T-S relationship.…”