Vertical stratification of bacterial communities driven by multiple environmental factors in the waters (0–5000 m) off the Galician coast (NW Iberian margin)

Abstract

The processes mediated by microbial planktonic communities occur along the entire water column, yet the microbial activity and composition have been studied mainly in surface waters. This research examined the vertical variation in bacterial abundance, activity and community composition and structure from surface down to 5000 m depth following a longitudinal transect off the Galician coast (NW Iberian margin, from 43ºN, 9ºW to 43ºN, 15ºW). Community activity and composition changed with depth. The leucine incorporation rates decreased from the euphotic layer to the bathypelagic waters by three orders of magnitude, whereas prokaryotic abundance decreased only by one order of magnitude. The relative abundance of SAR11 and Alteromonas, determined by catalyzed reported deposition fluorescence in situ hybridization (CARD-FISH), decreased with depth. Meanwhile, the contribution of SAR 202 and SAR324 was significantly higher in the deeper layers (i.e. NEADW, North East Atlantic Deep Water and LDW, Lower Deep Water) than in the euphotic zone. Bacterial community structure, assessed by Automated Ribosomal Intergenic Spacer Analysis (ARISA), was depth-specific. A distance based linear model (DistLM) revealed that the variability found in bacterial community structure was mainly explained by temperature nitrate, phosphate, dissolved organic matter (DOM) fluorescence, prokaryotic abundance, leucine incorporation and to a lesser extent salinity, oxygen, CDOM absorbance and dissolved organic carbon. Our results displayed a bacterial community structure shaped not only by depth-related physicochemical features but also by DOM quality, indicating that different prokaryotic taxa have the potential to metabolize particular DOM sources.

High dark inorganic carbon fixation rates by specific microbial groups in the Atlantic off the Galician coast (NW Iberian margin)

“…The contribution of Bacteria to the total microbial community decreased from the euphotic zone to bathypelagic waters while the relative abundance of Thaumarchaeota increases with depth (Guerrero‐Feijóo et al ., ). The contribution of the most abundant bacterial taxa to the total bacterial abundance was depth‐specific, showing that the relative abundance of SAR11 and Alteromonas decreased with depth and the contribution of SAR202 and SAR324 was increasing towards deeper waters (Dobal‐Amador et al ., ). In this study, dark DIC fixation of the bulk microbial community and of the most abundant deep‐water bacterial phylotypes was determined using the MICRO‐CARD‐FISH approach.…”

“…Recent metagenomic analyses have found genes encoding different subunits of the carbon monoxide dehytrogenase associated with Alteromonas (Smedile et al ., ). The high DIC uptake (particularly in the SSLs) by these taxa could be related to transporters of amino acids and TonB involved in the transport of carbohydrates (Baker et al ., ) and the availability of organic matter compounds easily degradable in the subsurface and upper mesopelagic waters off the Galician waters (Dobal‐Amador et al ., ; Guerrero‐Feijóo et al ., ), which might favour anaplerotic metabolism (Erb, ; Sauer and Eikmanns, ). In contrast to SAR406 and Alteromonas , most members of the SAR202 clade did not fix DIC or their activity was below the detection limit (see Fig.…”

“…The filters for catalyzed reported deposition fluorescence in situ hybridization (CARD-FISH) were embedded in low-gelling point agarose and incubated with lysozyme for Bacteria and specific bacterial groups or with proteinase-K for Thaumarchaeota following the method described in Teira and colleagues (2004). Filters were cut into sections and hybridized with horseradish peroxidase (HRP)-labelled oligonucleotide probes (see details of the probe sequences and hybridization conditions used in the CARD-FISH in Dobal-Amador et al, 2016;Guerrero-Feij oo et al, 2017), followed by tyramide-Alexa488 signal amplification. Autoradiographic development was conducted by transferring hybridized filter sections onto slides coated with photographic emulsion (type NTB-2 melted at 438C for 1 h; Teira et al, 2004).…”

Changes in Marine Prokaryote Composition with Season and Depth Over an Arctic Polar Year

“…Whilst we recorded generally higher levels of all three taxa in winter surface and year-round deeper waters, active populations were still detected in surface waters in summer months, albeit at much lower levels. The Chloroflexi-type SAR202 cluster is also typical and highly abundant in mesopelagic waters (Morris et al, 2004;Varela et al, 2008;Arístegui et al, 2009;Dobal-Amador et al, 2016). Recent studies have shown the Chloroflexi to be well adapted to deeper oligotrophic waters and to efficiently utilize recalcitrant organic compounds uptake, such as those found in the mesopelagic zone (Yilmaz et al, 2016).…”

Water mass mixing shapes bacterial biogeography in a highly hydrodynamic region of the Southern Ocean

“…Even though many studies have shown that distinguishable oceanic water bodies harbour different microbial communities (Pinhassi et al ., ; Díez et al ., ; Tamburini et al ., ; Celussi et al ., ; Galand et al ., ; Agogué et al ., ; Ghiglione et al ., ; Sul et al ., ; Han et al ., ; Techtmann et al ., ; Dobal‐Amador et al ., ), only a few of them have directly tackled the role of dispersal limitation by factoring out the effect of environmental selection (Hamdan et al ., ; Wilkins et al ., ). As selection seems to have a stronger influence on microbial biogeography than dispersal (Hanson et al ., ), historical processes may go undetected or underestimated in studies that emphasize environmental gradients (e.g., comparison of very distinct environments such as surface vs. meso‐ and bathypelagic water masses, or latitudinal distances of thousands of kilometers).…”