Short-term effect of a temperature gradient on the activity of methanogenic archaea and associated methane fluxes in different types of Mediterranean wetlands

Background Mediterranean wetlands play an important role in carbon cycling, partly due to the metabolic activity of the prokaryotic communities inhabiting these ecosystems. Among the different metabolisms involved, the methanogenesis carried out by methanogenic archaea is of great interest in the current context of global warming, as methane is a powerful greenhouse gas. Mediterranean wetlands, however, are very heterogeneous, and both the structure of prokaryotic communities and their metabolic activities vary greatly and are shaped by different environmental factors. This study analysed the short-term effect of different temperatures on methane fluxes and the expression of genes related to methanogenesis in the sediment of different Mediterranean wetlands. Results The increase in incubation temperatures caused the rise of methane emissions and the overexpression of the mcrA gene, which is involved in the final stage of methanogenesis, though this pattern was demonstrated for non-saline waters in low water renewal sites, whereas saline water system did not display these responses. In addition, a significant relation was observed between bioinformatically inferred methanogenesis and the amount of mcrA gene transcripts also for non-saline waters in low water renewal sites. Furthermore, data suggested that rising temperatures may influence competition for different metabolic substrates between methanogenic archaea and sulphate-reducing bacteria, thus determining the methane fluxes in Mediterranean wetlands. Conclusions Our results allowed us to infer the effects of a general increase in temperatures on methane emissions and the activity of methanogenic archaea in Mediterranean wetlands. Overall, these results may be helpful in improving the management of these ecosystems considering current and future climate change scenarios.