Sunken woods on the ocean floor provide diverse specialized habitats for microorganisms

Abstract

Marine waterlogged woods on the ocean floor provide the foundation for an ecosystem resulting in high biomass and potentially high macrofaunal diversity, similarly to other large organic falls. However, the microorganisms forming the base of wood fall ecosystems remain poorly known. To study the microbial diversity and community structure of sunken woods, we analyzed over 2800 cloned archaeal and bacterial 16S rRNA gene sequences from samples with different geographic locations, depths, and immersion times. The microbial communities from different wood falls were diverse, suggesting that sunken woods provide wide‐ranging niches for microorganisms. Microorganisms dwelling at sunken woods change with time of immersion most likely due to a change in chemistry of the wood. We demonstrate, for the first time in sunken woods, the co‐occurrence of free‐living sulfate‐reducing bacteria and methanogens and the presence of sulfide oxidizers. These microorganisms were similar to those of other anaerobic chemoautotrophic environments suggesting that large organic falls can provide similar reduced habitats. Furthermore, quantification of phylogenetic patterns of microbial community assembly indicated that environmental forces (habitat filtering) determined sunken wood microbial community structure at all degradation phases of marine woodfalls. We also include a detailed discussion on novel archaeal and bacterial phylotypes in this newly explored biohabitat.

Temporal and spatial constraints on community assembly during microbial colonization of wood in seawater

“…In this case, only one specific fraction of the environmental bacterial pool is able to colonize and persist in the wood matrix when colonization starts. This abiotic selection process is called habitat filtering (Webb et al, 2002) and was shown earlier to structure wood fall communities on the sea floor (Fagervold et al, 2012). Interestingly, the level of habitat filtering decreased with time.…”

“…Wood fall bacterial communities that were early characterized according to their physical action on the wood matrix (Mouzouras et al, 1988;Jurgens et al, 2003), and first described through the isolation of cultivable representatives (Cundell and Mitchell, 1977;Austin et al, 1979), were precisely identified only recently by molecular tools. A large cloning and sequencing effort gave the first insights into the diversity of natural wood fall bacterial and archaeal assemblages (Fagervold et al, 2012). It demonstrated the presence of sequences associated to possible fermenters and sulfide-oxidizing bacteria, as well as the co-occurrence of free-living sulfate-reducing bacteria.…”

“…Archaea have also been detected on wood falls, especially on samples with substantial signs of decay (Palacios et al, 2009). They are potentially involved in the production of methane (Fagervold et al, 2012), but the observation of the association of a giant Thaumarchaeota with sulfur-oxidizing bacteria (Muller et al, 2010) suggests the presence of diverse archaeal metabolisms on wood falls. The first molecular descriptions of wood microbes gave clues to potential metabolisms associated with the degradation of wood in the marine environment.…”

Microbial Communities in Sunken Wood Are Structured by Wood-Boring Bivalves and Location in a Submarine Canyon

“…As submerged woods become anaerobic after only a few days [15], it is expected that pathways associated to fermentation, with electron acceptors other than oxygen, play a significant role. Indeed, studies on sunken wood in the deep Mediterranean revealed that this substrate can harbor rich bacterial communities [16]–[18] including fermenting bacteria, microorganisms involved in sulfur cycling and methane production, and new clades of Bacteria and Archaea with unknown physiologies [18]. As the application of molecular techniques has revealed a large diversity of microbes associated to sunken woods, they have also allowed a first understanding of the ecology of sunken wood microbial communities, showing that wood type, immersion time and the environmental conditions surrounding submerged wood may promote contrasted bacterial communities [19], [16]–[18].…”

Redescription of wood-associated tanaidacean Protanais birsteini (Kudinova-Pasternak, 1970) and its relationship within the Tanaididae

“…Xylophagous invertebrates physically modify solid wood tissue into three-dimensional habitat attractive to numerous benthic organisms and their predators (Bienhold et al, 2013, Bessette et al, 2014, McClain and Barry, 2014. These pioneer organisms consume oxygen and are responsible for the development of anaerobic chemoautotrophic conditions that in consequence support a growth of microorganisms involved in methane and sulfur cycles (Fagervold et al, 2012).…”