Rapid shifts in pond sediment microbiota in response to high ambient temperature in a water-sediment microcosm.

Unlike the extensive research on the response of soil microorganisms to high ambient temperature (HTA), the response of sediment microorganisms to HTA remains unclear. Understanding the response of sediment microorganisms to HTA is important to forecast their impacts on ecosystems and climate warming under projected climate change scenarios. Against the background of climate warming and frequent high ambient temperatures in summer, we conducted a laboratory incubation experiment to clarify the unique assembly characteristics of pond sediment bacterial communities at different temperatures (4, 10, 15, 25, 30 and 35 °C). The results showed that the structure and function of the microbial community in pond sediments at 35 °C were different from those under other temperatures; the microbial community structure at 35 °C had the most large modules and an average module size. Temperature and dissolved oxygen influenced the microbial community network modularity. The CO emission rates of pond sediments at 35 °C were significantly higher than those at other temperatures. At 35 °C, heterogeneous selection was the most important assembly process. Additionally, warming altered the microbial network structure and ecosystem functioning but not the microbial diversity or community composition, which may be related to horizontal gene transfer. Revealing the rapid response of pond sediment microorganisms to HTA is important for identifying their role in nutrient cycling and assessing the ecological impacts of climate warming and high ambient temperatures on inland water sediments.