Effects of dissolved oxygen on the decomposers and decomposition of plant litter in lake ecosystem

Plant litter releases an amount of carbon, nitrogen and phosphorus during decomposition, which potentially has significant impacts on carbon, nitrogen, and phosphorus cycles and lake eutrophication. Dissolved oxygen (DO) plays an important role in changing the decomposition rate of litter and the major decomposers of litter. The decomposition rates of Phragmites australis, Triarrhena lutarioriparia and Carex spp under four DO concentration conditions (anaerobic group (0 mg/L DO), low DO group (6 mg/L DO), medium DO group (7 mg/L DO), high DO group (8 mg/L DO)) were measured in the laboratory for 120 days. The microorganisms community structure under the four DO conditions was tested to explore the major litter decomposer. The results showed that affected by litter quality, the decomposition rates of the three litters followed the order: Triarrhena lutarioriparia > Phragmites australis > Carex spp. A large amount of carbon, nitrogen and phosphorus were stored in water over litter decomposition. DO accelerated carbon and nitrogen release and promoted the decomposition of litter. The litter of high DO group decomposed 25.5%–42.0% more than that of anaerobic group. DO significantly affected the microbial community structure, and the proportion of microorganisms with the ability to decompose litter was higher in high DO group.