Hydrodynamic conditions influenced by river sinuosity may alter carbon (e.g., carbon dioxide and methane) emissions and microbial communities responsible for nutrient turnover. However, knowledge is lacking for the linkage between carbon emission and bacterial community in disturbed environments caused by river sinuosity. Here, the alternative states of benthic bacterial communities under the hydrodynamic conditions in river bends and the feedback to carbon emissions were investigated for the first time through the experiment of channels with different sinuosity combining hydrodynamic profiling, high-throughput sequencing and ecological theory. In this study, bimodal distributions combined with potential analysis showed direct evidence of bistability and demonstrated that increasing hydrodynamic conditions over a threshold (i.e., bottom velocity >
0.73 cm s