Bacterial communities as bioindicators of climate change in freshwater ecosystems: Tank bromeliads as model systems

Climate change, characterized by rising temperatures and extreme weather events, threatens tropical freshwater ecosystems. However, despite their global relevance, research on the effects of climate change on tropical environments remains scarce. Tank bromeliads, functioning as natural microcosms, offer a valuable model for studying tropical ecosystems. These plants host complex communities, including microorganisms, which may serve as bioindicators of climate change due to their adaptability and ubiquity. This study used 16S rRNA gene sequencing to examine bacterial communities in bromeliads along a latitudinal gradient on the Brazilian coast, using a space-for-time substitution approach. The analysis of water and sediment samples from 60 bromeliads across 10 sites revealed the phyla Pseudomonadota, Acidobacteriota, and Bacillota as the predominant members. Alpha diversity metrics were positively correlated with latitude and negatively with atmospheric temperature, while dbRDA and Mantel tests identified atmospheric temperature and pH as key factors influencing bacterial communities. The study showed that deterministic processes shaped community assembly; however higher temperatures led to stochastic processes, altering bacterial composition. Network analysis revealed that rare species were key connectors in highly interconnected modules, suggesting resilience in the face of environmental changes. However, the vulnerability of these rare species to stochastic processes raises concerns about community stability under climate change. This study provides the first detailed characterization of bacterial communities and co-occurrence networks in tank bromeliads, supporting their use as model systems for monitoring the impacts of climate change on tropical freshwater ecosystems.