Methanogenesis in sediments from deep lakes at different temperatures (2–70°C)

Abstract

Methanogenic degradation of organic matter occurs in a wide temperature range from psychrophilic to extreme thermophilic conditions. Mesophilic and thermophilic methanogenesis is relatively well investigated, but little is known about low temperature methanogenesis and psychrophilic methanogenic communities. The aim of the present work was to study methanogenesis in a wide range of temperatures with samples from sediments of deep lakes. These sediments may be considered deposits of different types of microorganisms, which are constantly exposed to low temperatures. The main question was how psychrophilic methanogenic microbial communities compare to mesophilic and thermophilic ones. Methanogenesis in a temperature range of 2–70°C was investigated using sediment samples from Baldegger lake (65 m) and Soppen lake (25 m), Switzerland. Methane production from organic matter of sediments occurred at all temperatures tested. An exponential dependence of methane production rate was found between 2 and 30°C. Methanogenesis occurred even at 70°C. At the same time stable methane production from organic matter of sediments was observed at temperatures below 10°C. Methanogenic microbial communities were enriched at different temperatures. The communities enriched at 4–8°C had the highest activity at low temperatures indicating that a specific psychrophilic community exists. Addition of substrates such as cellulose, volatile fatty acids (butyrate, propionate, acetate), methanol and H2/CO2 stimulated methane production at all temperatures. H2/CO2 as well as methanol were directly converted to methane under thermophilic conditions. At low temperatures these substrates were converted to methane by a two-step process. First acetate was formed, followed by methane production from acetate. When acetate concentrations were high, acetoclastic methanogenesis was inhibited at low temperatures. This reaction appears to be one of the “bottle neck” in psychrophilic methanogenesis.

Eddy covariance flux measurements confirm extreme CH<sub>4</sub> emissions from a Swiss hydropower reservoir and resolve their short-term variability

“…Along with the reactivity of the organic matter, temperature is an important regulator of organic matter degradation in sediments (Gudasz et al, 2010;Kelly and Chynoweth, 1981;Nozhevnikova et al, 1997), and consequently also of CH 4 production (Bastviken, 2009). However, at the shorter timescales of the present study, variations in temperature are small and hence the effect on methanogenesis is most likely also smaller.…”

Spatial distribution of methane in the Lake Biwa sediments and its carbon isotopic compositions.

“…Previous studies, however, have often reported that acetate fermentation is the major pathway of methanogenesis in profundal lake sediments (Schulz and Conrad, 1996;Schulz et al, 1997;Nozhevnikova et al, 1997). This inconsistency with previous studies might be explained by indirect methane production from CO 2 via autotrophic acetogenesis (Nozhevnikova et al, 1997;Hornibrook et al, 2000). Carbon isotope fractionation for acetate production from H 2 and CO 2 was reported to be compatible with that for the methanogenesis of the CO 2 reduction pathway (Gelwicks et al, 1989).…”

“…Two primary metabolic pathways are generally recognized for biological methanogenesis: fermentation of acetate and reduction of carbon dioxide, and the low δ 13 C CH 4 values and high αcCO 2 -CH 4 values both suggested that methane in the sediments of Lake Biwa is predominantly produced via CO 2 reduction pathway (Whiticar et al, 1986;Sugimoto and Wada, 1993). Previous studies, however, have often reported that acetate fermentation is the major pathway of methanogenesis in profundal lake sediments (Schulz and Conrad, 1996;Schulz et al, 1997;Nozhevnikova et al, 1997). This inconsistency with previous studies might be explained by indirect methane production from CO 2 via autotrophic acetogenesis (Nozhevnikova et al, 1997;Hornibrook et al, 2000).…”

Temporal evolution of methane cycling and phylogenetic diversity of archaea in sediments from a deep-sea whale-fall in Monterey Canyon, California

“…At low temperatures, hydrogenotrophic methane production is thought to be inhibited, shifting methanogenesis toward acetate or C1 compounds (Zeikus and Winfrey, 1976;Gunnarsson and Ronnow, 1982;Schulz and Conrad, 1996;Nozhevnikova et al, 1997). Despite this limitation, a few species of Methanogenium have been observed and even isolated from psychrophilic sulfate-rich marine sediments (Parkes et al, 1990;Franzmann and Liu, 1997;Chong et al, 2002;Purdy et al, 2003;Kendall and Boone, 2006).…”