Hydrogen export from intertidal cyanobacterial mats: sources, fluxes, and the influence of community composition. Hydrogen export in microbial mats

We examined H2 accumulation and export in 3 types of greenhouse-reared mats kept under natural light-dark conditions and controlled wetting and drying cycles that simulate low-, mid- and high-tidal height periodicity. All mats released H2 reproducibly and sustainably for longer than 1.5 years of incubation. Net H2 export took place in a pulsed daily manner, starting soon after dusk, and waning in the early morning hours, as photosynthesis resumed. 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 H2 export, as was the relatively low abundance of methanogens and sulfate reducers.