engleski

Distribution of methanotrophs along the oxycline in two lake systems

Freshwater lakes are dynamic environments that emit significant amount of greenhouse gasses to the atmosphere, in particular methane – a major regulator of global climate. Methanotrophs can mitigate that emission by aerobic and anaerobic oxidation of methane from anoxic layers of the lake that can contain high methane concentrations. In order to understand the microbial significance in methane cycling we investigated two lake systems in Croatia with different climate, trophic status and lake type – Plitvice Lakes and Baćina Lakes. Water samples from different depths were collected from May to November 2021 and environmental parameters were measured in situ using a multiparameter sonde (EXO2, YSI, USA). Microbial community was taxonomically determined using 16S rRNA gene pair-end sequencing method and statistical analysis was performed using R software (R Core Team, 2021). Dominant phyla in both lake systems were Actinobacteriota, Bacteroidota, Cyanobacteria, Proteobacteria and Verrucomicrobiota. In some of the samples, we determined the presence of the aerobic methanotrophs, above and below the oxycline, with the most abundant genera being Crenothrix, Methylomonas, Methylocystis and order Methylacidiphilales. Their community structure is lake-specific and differs based on their lifestyle (free-living and particle-associated). Also, we determined seasonal changes in microbial communities in all lakes. Our results show that aerobic methanotrophs have the potential for methane oxidation even in oxygen-deficient environments.

methane oxidation ; anoxia ; amplicon sequencing ; climate change

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