| description |
In this preliminary study we addressed the following research questions: (i) What is driving the massive biofilm growth? (ii) Who are the key players contributing to ecosystem processes? (iii) Does microbial community composition in the cave reflect intrinsic physicochemical gradients? We sampled microbial communities from horizontal and vertical transects in the cave employing16S rRNA sequencing thereby identifying bacterial taxa. Gas emissions were evaluated by means of gas chromatography and the uptake of methane into biofilm biomass was evaluated by stable isotope analysis. Potential oxidation rates for methane were evaluated in the laboratory.Stable isotope analysis of biofilms indicates that methane gas seeping into the cave from a deep subsurface origin serves as main driver of biofilm formation. A high abundance and diversity of methanotrophs primarily consisting of Methylococcales (Gammaproteobacteria) and methylotrophic Methylotenera sp. (Alphaproteobacteria) substantiated this finding. Detailed analysis of upwelling brackish water revealed elevated iodine loads and an inflow of iron-oxidizing Gallionella sp. as well as diverse sulfur-oxidizing bacteria. Surprisingly, distinct methane oxidation potentials were measured in different biofilm compartments (submerged, wall, ceiling) and suggested an importance of as-yet unidentified electron donors especially in biofilms on the ceiling. |