High concentrations of dissolved biogenic methane associated with cyanobacterial blooms in East African lake surface water
Fazi S.[1; 11]; Amalfitano S.[1; 11]; Venturi S.[2; 3]; Pacini N.[4; 5]; Vazquez E.[6]; Olaka L.A.[7]; Tassi F.[2; 3]; Crognale S.[1]; Herzsprung P.[8]; Lechtenfeld O.J.[8]; Cabassi J.[3]; Capecchiacci F.[2; 3]; Rossetti S.[1]; Yakimov M.M.[9]; Vaselli O.[2; 3]; Harper D.M.[5; 10]; Butturini A.[6];
The contribution of oxic methane production to greenhouse gas emissions from lakes is
globally relevant, yet uncertainties remain about the levels up to which methanogenesis can
counterbalance methanotrophy by leading to CH4 oversaturation in productive surface
waters. Here, we explored the biogeochemical and microbial community variation patterns in
a meromictic soda lake, in the East African Rift Valley (Kenya), showing an extraordinarily
high concentration of methane in oxic waters (up to 156 micromol L-1
). Vertical profiles of
dissolved gases and their isotopic signature indicated a biogenic origin of CH4. A bloom of
Oxyphotobacteria co-occurred with abundant hydrogenotrophic and acetoclastic methano-gens, mostly found within suspended aggregates promoting the interactions between Bacteria, Cyanobacteria, and Archaea. Moreover, aggregate sedimentation appeared critical in
connecting the lake compartments through biomass and organic matter transfer. Our findings
provide insights into understanding how hydrogeochemical features of a meromictic soda
lake, the origin of carbon sources, and the microbial community profiles, could promote
methane oversaturation and production up to exceptionally high rates.
2021 - Articolo in rivista
Communications biology 4 (2021): 1–12. doi:10.1038/s42003-021-02365-x
Keywords: East African Rift Valley (Kenya);