The effects of climate warming on microbe-mediated mechanisms of sediment carbon emission.

Due to significant differences in biotic and abiotic properties of soils compared to those of sediments, the predicted underlying microbe-mediated mechanisms of soil carbon emissions in response to warming may not be applicable for estimating similar emissions from inland water sediments. We addressed this issue by incubating different types of sediments, (including lake, small river, and pond sediments) collected from 36 sites across the Yangtze River basin, under short-term experimental warming to explore the effects of climate warming on sediment carbon emission and the underlying microbe-mediated mechanisms. Our results indicated that under climate warming CO emissions were affected more than CH emissions, and that pond sediments may yield a greater relative contribution of CO to total carbon emissions than lake and river sediments. Warming-induced CO and CH increases involve different microbe-mediated mechanisms; Warming-induced sediment CO emissions were predicted to be directly positively driven by microbial community network modularity, which was significantly negatively affected by the quality and quantity of organic carbon and warming-induced variations in dissolved oxygen, Conversely, warming-induced sediment CH emissions were predicted to be directly positively driven by microbial community network complexity, which was significantly negatively affected by warming-induced variations in pH. Our findings suggest that biotic and abiotic drivers for sediment CO and CH emissions in response to climate warming should be considered separately when predicting sediment organic carbon decomposition dynamics resulting from climate change.