中文摘要：

以太湖梅梁湾沉积物环境为研究对象,通过室内培养试验,研究上覆水不同C/N比条件对沉积物中反硝化（nirS、nirK）及氨氧化功能基因（古菌AOA-amoA、细菌AOB-amoA）丰度的影响,实验设计硝氮水平为2.0和5.0mg·L-1,C/N为0.5、2、4、6、10、14.结果表明,所有实验组样品在60天的培养周期中,反硝化功能基因丰度与本底值相比有所上升,但对C/N比变化响应不显著;氨氧化功能基因丰度对C/N比的变化有响应,当C/N比大于一定比值时,其丰度由初期的显著上升变化为显著下降.其中,氨氧化古菌（AOA-amoA）丰度对C/N比变化响应更显著.相关性分析表明,系统中硝酸盐氮浓度与氨氧化功能基因丰度呈显著相关（r2=0.551,P〈0.05）,当氨氧化功能基因丰度较高时,来源于沉积物中氨氮的硝化产物使得系统中硝酸盐氮趋于累积.

英文摘要：

This study investigated the relationships between C/N ratios in overlying water and abundances of denitrification and ammonium oxidation functional genes（nirK,nirS,AOA-amoA and AOB-amoA）in sediments sampled from Meiliang Bay,Taihu Lake.The experiment was conducted under two nitrate substrate concentrations of 2.0and5.0mg·L-1;and the C/N ratios was selected to be 0.5、2、4、6、10、14.The results showed that during 60-day incubation,the abundances of denitrification functional genes in all samples have increased,compared to the background abundances,but showed no significant response to changes in C/N ratios,while the abundance of ammonium oxidation functional genes varied with the changing C/N ratios.When C/N ratio exceed a certain value,the abundance of ammonium oxidation functional genes tended to decrease after an early increase,and AOA-amoAabundance respon-ded to the different C/N ratios more evidently.Correlation analysis indicated that the transformation rates of nitrate significantly correlated to the abundance of ammonium oxidation genes（r2=0.551,P0.05）.When the abundance of ammonium oxidation genes was at high level,nitrate tended to accumulate in the system,which might result from the nitrification of ammonia nitrogen in sediments.