科研之友
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摘要
Microbial mats from marine intertidal settings have been reported to release significant quantities of H-2, in a unique trait among other mats and microbial communities. However, the H-2 source and ecophysiological mechanisms that enable its export are not well understood. We examined H-2 accumulation and export in three types of greenhouse-reared mats, from the intertidal region of Guerrero Negro, Mexico, and kept under natural light-dark conditions and wetting and drying cycles simulating low-, mid- and high-tidal height periodicity. All mats released H-2 reproducibly and sustainably for 1.5 years. Net H-2 export took place in a pulsed daily manner, starting after dusk, and waning in the morning, as photosynthesis resumed. Mid- and low-tidal mats developed high concentrations, capable of sustaining export fluxes that represented 2-4% of the water split through primary productivity. Neither N-2 fixation nor direct photolytic hydrogenogenesis was significant to this H-2 export, which was fermentative in origin, variable among mats, originating from cyanobacterial photosynthate. Analyses of community composition by pyrosequencing of 16S rRNA and hoxH genes indicate that filamentous non-heterocystous cyanobacteria (e.g. Lyngbya, Microcoleus) were important in the process of H-2 export, as was the relatively low abundance and activity of methanogens and sulfate reducers.
- 出版日期2015-10
