Offre et al. also found the changes in the relative abundance of the specific archaeal amoA genes during active nitrification in soil microcosms incubated at 30uC. In the present study, the copy numbers of the archaeal amoA gene increased significantly in the microcosms incubated at 35uC. Due to the lack of the relative contribution analysis of archaeal and bacterial ammonia oxidizers, we do not yet know whether this increase in the abundance of archaeal amoA gene would affect the nitrification rates in the sediment samples. Further studies are needed to investigate the effects of ammonia oxidation inhibitor on the growth of ammonia oxidizer and nitrification kinetics and elucidate the relative contributions of archaeal and bacterial ammonia oxidizers in the freshwater ecosystem under different temperature conditions. The coupled nitrification-denitrification processes could remove high percentages of anthropogenic nitrogen pollution, which is of particular significance in the eutrophic lake ecosystem. With the increasing temperature, ammonia oxidation rate and the nitrite production rate increased, which could result in the NH3-N consumption and NO3-N accumulation. In the present study, the concentrations of NH3-N reduced after incubation, indicating the consumption of ammonia through nitrification in sediment samples. Stark investigated the influence of temperature on ammonia oxidation and reported that the optimum temperature for potential nitrification was in the range of 20uC�C37uC. Avrahami et al. also reported a decrease in ammonium concentration in microcosms of an Monensin sodium salt agricultural soil after short and long incubation. In the present study, the amount of TN decreased in all treatment groups compared to the pre-incubation samples suggesting the nitrogen loss after incubation. The remained TN amount SB 206553 hydrochloride correlated negatively with temperature. Higher temperatures would induce the decreased dissolved oxygen in the sediments, which could activate anaerobes and the denitrification activity, promoting the NO3-N consumption and N2O production. Avrahami et al. also demonstrated the release rates of N2O increased monotonously between 4 and 37uC in the soil microcosms. This was also confirmed by the accumulation of NO3-N in the 35uC treatment that was not significantly higher than the other two groups in the present study. Variation in the temperature could change the abundances and community compositions of AOA and AOB in the lake sediments and therefore affect the nitrogen cycling process. The coupled nitrification-denitrification processes play pivotal roles in removing the nitrogen from the eutrophic lake ecosystem.