Effects Of Climate Warming On Aquatic Bacterial Community Structure And Decomposition Of Submerged Macrophytes Litter

Under future climate change conditions,extreme climate events such as heat waves will also occur with greater frequency and intensity.Freshwater ecosystems are particularly vulnerable to climate warming,microorganisms are recognized as sensors of external disturbance in freshwater ecosystems,and it is crucial to understand how climate warming will affects the whole microbial communities and functions in shallow lakes.In this study,we use high-throughput sequencing to analyze bacterial community composition in the 18 outdoor mesocosms under 3 temperature scenarios(ambient temperature,constant warming and variable warming).We aim to reveal(1)effects of climate warmings on planktonic and sedimentary bacterial communities at seasonal scale;(2)decomposition of submerged macrophyte litter and response of related bacterial communities to climate warming.The main research results of this study are as follows:(1)The two warming treatments did not affect the diversity and richness of planktonic bacteria in any season,and only increased those of sedimentary bacteria in winter;The community structure of planktonic bacteria had no obvious clustering in seasons or among treatments,and the community structure of each sample differed greatly.The obvious clustering of sedimentary bacteria in different seasons indicates that the community structure had significant seasonality,and there is little difference in the community structure within the group.In addition,consistent with the diversity changes,the constant warming and variable warming have significant effects on the community structure of sedimentary bacteria in winter;The planktonic and sedimentary bacteria network in each treatment was mainly composed of positive correlation,indicating that the symbiotic relationship was dominant among the bacteria.Both constant and variable warming increased the gap of proportion of positive correlation between planktonic and sedimentary bacterial networks,suggesting that planktonic bacteria network may became fragile and vulnerable to interference while sedimentary bacteria network was developing towards a more stable direction,this suggested that sediment may provide more ecological niches and serve as a refuge for aquatic microorganisms under climate warming.(2)Warming treatments may accelerate the decomposition of submerged macrophyte litter in shallow lake ecosystems,and increase the diversity of decomposition-related bacteria with community composition changed the relative abundance of Proteobacteria and Choloflexi while that of Firmicutes decreased.