Poster, VAAM-Tagung, Jena: 19.03.2006 - 22.03.2006
Abstract:
Methanogenesis is the main terminal electron sink in peats and fermentation products serve as substrates for methanogens. Activities of fermenters and methanogens from an acidic peat (pH 4.8) were evaluated from 0-40 cm of depth in anoxic microcosms. Sulphate (10 µM) and nitrate (20 µM) concentrations indicated that these electron acceptors were neglectible. Water content ranged from 60-90 %. Pore water concentrations of formate, lactate, and acetate were 187.4, 15.5, and 2.9 µM, respectively. Nonsupplemented peat produced CO2, CH4 and organic acids. CO2- and CH4-accumulation over time decreased with depth in slurries and field fresh peat at 15 °C. In slurries, formate and lactate were consumed while acetate and propionate were produced. CO2 and CH4 were produced from 2-40 °C and from pH 2-7 with optimal activity at 30 °C and pH 7, respectively, indicating that fermenters and methanogens are temperature- and pH-limited in situ. When methanogenesis was inhibited with 2-bromo-ethane sulphonate (BES), monomers of common biopolymers, i.e. glucose, xylose, and N-acetylglucosamine, stimulated the formation of H2, CO2, and organic acids. The production of gases and acids increased with increasing substrate concentrations. Without BES, glucose also stimulated CH4-production. H2-formation was 2-3-fold lower compared to incubations with BES, and H2 was subsequently consumed, indicating that H2 was a CH4-precursor. The production of CH4 was stimulated by formate and H2/CO2; methanol and acetate had no effect, indicating the presence of hydrogenotrophic and formate-consuming methanogens. The collective results suggest that this acidic peat harbours sugar-consuming fermenters that provide formate and H2/CO2 to methanogens.