Skip to main content

Biodiversity and functions of microbial communities associated with sunken woods in marine environments

Final Activity Report Summary - SUNKEN WOOD MICRODIV (Biodiversity and functions of microbial communities associated with sunken woods in marine environments)

Different sources of imported, organic matter carried down to the deepest parts of all seas could enhance the species' richness of sediment-dwelling communities where organisms are highly food-limited and rely primarily on organic material from upper layers. Furthermore, when deposited in marine sediments, large organic falls undergo sufficiently steady decay for oxygen to be depleted, attracting anaerobic living forms. The phylogenetic resemblance and overlap in species of metazoans living in woods or large animal remains with those of highly reduced environments like hydrothermal vents and cold seeps has lead to the hypothesis that deep-sea organic rich matter deposits could play a major role in the dispersion and evolution of chemoautotrophic communities at the ocean basin.

Chemosynthetic symbiotic and free-living bacteria drive these communities. No culture-independent studies on free-living microorganisms at sunken woods have been conducted so far. We used culture-independent methods to study the microbial communities on both artificially immersed and naturally sunken wood logs in geographically distant coastal and deep-sea environments. We used a fingerprinting method called Capillary electrophoresis single stranded conformation polymorphisms (CE-SSCP) to fingerprint the archaea and bacteria communities living on and within the woods to determine their resemblance among samples. Scanning electron microscopy revealed extensive microbial erosion of the wood cell walls and different decay patterns with length of immersion. Furthermore, posterior ribosomal Ribonucleic acid (RNA) gene (rDNA) cloning and sequencing of target samples gave clues on the actual diversity and phylogenetic resemblance of the main microbial players responsible of energy and carbon flows.

Our results broadened our narrow knowledge on the microbial biofilms that developed around woods in marine environments and gave clues on the ecological importance of these organic island deposits for the dispersion of chemosynthetic communities at the ocean basin.