Microbial communities associated with benthic faunal assemblages at cold seep sediments of the Sonora Margin, Guaymas Basin

Abstract

The Sonora Margin cold seeps present a seafloor mosaic pattern consisting of different faunal assemblages and microbial mats. To better understand if sedimentary microbial communities reflect this patchy distribution, all major habitats were investigated using four complementary approaches: 16S rRNA gene sequence 454 pyrosequencing, quantitative polymerase chain reaction, fluorescence in situ hybridization and geochemistry analyses. This study reveals that sediments populated by different surface assemblages show distinct porewater geochemistry features and are associated with distinct microbial communities. In the sediments underlying the microbial mat and the surrounding macrofauna, microbial communities were dominated by anaerobic methane oxidizers (archaeal anaerobic methanotroph ANME) and sulfate-reducing Deltaproteobacteria. In contrast, sediment-associated microbial communities underlying the megafauna habitats (vesicomyids and siboglinids) were characterized by a lower biomass and important proportions of the Marine Benthic Group D (MBG-D), Chloroflexi as well as filamentous Gammaproteobacteria and Deltaproteobacteria. Together, geochemical and microbial surveys indicate that porewater methane concentrations play an important role in the microbial community structure and subsequently in the establishment of the surface colonizers. Furthermore, presence and activity of the surface colonizers influence the underlying microbial communities probably because of modification of energy source availabilities.

Comparative Study of Guaymas Basin Microbiomes: Cold Seeps vs. Hydrothermal Vents Sediments

“…Indeed, the archaeal community in vesicomyid cold seep sediments was dominated by members of the Thermoplasmatales (MBG-D) (Figure 4, Figure S2, and Table S5). These Archaea have been previously proposed to be involved in organic matter degradation (Lloyd et al, 2013) and might thrive in cold seep sediments by degrading vesicomyid exudates (Joye et al, 2010;Pop Ristova et al, 2012;Cruaud et al, 2015). By contrast, thermophilic lineages (e.g., Methanopyrales, Thermoprotei) were detected in hydrothermal vent sediments colonized by vesicomyids (Table S5), confirming that this site was fueled by a hydrothermal fluid.…”

“…By contrast, thermophilic lineages (e.g., Methanopyrales, Thermoprotei) were detected in hydrothermal vent sediments colonized by vesicomyids (Table S5), confirming that this site was fueled by a hydrothermal fluid. Nonetheless, the archaeal community in hydrothermally influenced sediments was dominated by members of the Thaumarchaeota (MG-1) (Figure 4, Figure S2, and Table S5), previously identified in water column (DeLong, 1992) and detected in sediments outside seepage area of the Guaymas Basin (Vigneron et al, 2013;Cruaud et al, 2015). One hypothesis to explain the difference between microbial community of vent and seep vesicomyids habitats would be that the hydrothermal sampling site could not be continuously colonized by the bivalves but only be a transition zone for vesicomyids.…”

“…The Guaymas Basin is a unique environment which harbors not only hydrothermal chimneys, mounds (Callac et al, 2015) and hydrothermally impacted sediments (i.e., sediments percolated by hydrothermal fluid) (Teske et al, 2002) but also cold seep sediments (Vigneron et al, 2013;Cruaud et al, 2015), within few kilometers. In this study, area of hydrothermally impacted sediments and cold seep sediments were investigated to compare the microbial community compositions and potential functions present in these contrasted ecosystems in absence of physical borders and in a similar geochemical context characterized by the accumulation of organic-rich sediments.…”

“…Taxonomic assignments of the reads were performed as previously described in detail in Cruaud et al (2015) using the Mothur version of the Bayesian classifier (Schloss et al, 2009) on both SILVA database (release 119, 464,618 sequences of Bacteria and 18,797 sequences of Archaea, www.arb-silva.de) and an in-house database composed of deep-sea marine sediment sequences from reference publications updated and completed for this study using the SILVA database release 119, as described in Cruaud et al (2015) (2,860 bacterial and 978 archaeal sequences, Table S4). …”

“…Therefore, the Guaymas Basin represents a unique opportunity to directly compare hydrothermal vent and cold seep ecosystems. Previous investigations on the sedimentary microbial community compositions of the Guaymas Basin, from either but not both of these ecosystems, suggested that analogous microbial processes might occur, despite contrasted temperatures (Teske et al, 2002;Dhillon et al, 2003;McKay et al, 2012;Vigneron et al, 2013;Cruaud et al, 2015;Lever and Teske, 2015). However, these results remain hardly comparable since different methodologies were used.…”