Disturbance-Driven Reactive Oxygen Species Generation Promotes Organic Carbon Mineralization in Sediments of Lake Taihu.

Lake sediments are prone to disturbance from anthropogenic and natural processes, inducing O2 intrusion that can generate reactive oxygen species (ROS). However, the occurrence and accumulation of ROS production in O2-perturbed lake sediments are poorly documented. Herein, we investigated ROS production in oxygenated sediments from the sediment-water interface to a depth of 41 cm at 14 different sites in Lake Taihu, China. Results showed that ROS exhibited distinct depth-dependent variations, such that the concentrations of H2O2 and •OH increased with increasing depth, while those of O2•- peaked in 11-16 cm range. Autoclaving sterilization experiments revealed that the proportion of biotic ROS declined while those of abiotic ROS increased with increasing depth, with specific contribution determined by sediment characteristics. Surface-disturbed sediments contained rich and active microbial communities, with biotic processes contributing significantly to ROS production. Abiotic process became the dominant contributor in deep-disturbed sediments due to more reduced components. Random forest and partial least-squares path model analyses further demonstrated that physicochemical properties and bacteria community were primary drivers for ROS production in sediments. Moreover, the generated •OH significantly promoted the abiotic mineralization of sediment organic carbon, accounting for 7.0-32.4% of CO2 efflux. Our research expanded ROS distribution and demonstrated mechanisms for ROS production in lake sediments, which can contribute to a deeper understanding of the carbon cycle as well as pollutant attenuation in lake ecosystems.