Influência da redução das chuvas na dinâmica da comunidade microbiana em ecossistemas aquáticos

Abstract

Aquatic ecosystems are recognized as important carbon stocks, where the microbial community plays a central role in the degradation of dissolved organic matter. Such communities may be influenced by changes in the planet's climate, such as those related to precipitation regimes, with consequences still poorly understood for the functioning of aquatic ecosystems. Understanding the impact of climate change on microbial community and consequently on the metabolism of organic matter is therefore central to microbial ecology and ecosystem ecology. Based on predictive data on rainfall reduction, the present study evaluated how these reductions can influence microbial dynamics in relation to their metabolic processes, functional role, composition and diversity. The experiment was built using tank bromeliads as sampling units due to their realistic characteristics and high replicability, and considered four four different scenarios of rain to test how these changes influence the dynamics of the aquatic microbial community, considering the change in frequency and volume of rainfall. The results revealed changes in the functional profiles of the bacterial community, and increase of certain parameters related to its metabolism (bacterial production and bacterial growth efficiency) due to the decrease in volume and /or frequency of rain events, although without direct relation with changes of the composition of the bacterial community. These results indicate that changes in rainfall alter the bacterial biogeochemical environment by "selecting" metabolic pathways according to the availability of substrates and reagents for the biogeochemical reactions. On the other hand microbial groups could have high plasticity in the functions tested, explaining why the changes in the functional profiles were not related to changes in the composition of the bacterial community. Therefore, changes in pluviometric regimes may affect aquatic microbial metabolism, potentially altering microorganism-mediated processes, energy flow in aquatic chains and cycling of elements in ecosystems without major changes in the structure of microbial communities.