若尔盖花湖沉积物氨氧化与反硝化功能基因丰度垂向分布特征及其环境响应

若尔盖湿地作为中国最大的泥炭沼泽区,是生物地球化学循环的重要场所.本文以若尔盖湿地的花湖为研究对象,采集0～47 cm的沉积物样品,通过实时荧光定量PCR(qPCR)技术,探究沉积物中氨氧化(amoA)和反硝化(nirS、nirK、nosZ clade I)功能基因丰度的垂向分布特征,及其对环境因子的响应.结果表明:花湖沉积物中古菌amoA基因丰度在垂向分布上呈下降趋势,而nirS基因丰度呈上升趋势;古菌和细菌的amoA基因丰度相近,nirS基因丰度则远高于nirK基因,且氨氧化功能基因丰度整体上比反硝化功能基因低1～2个数量级.总氮(TN)、总磷(TP)、氨态氮(NH~+_4-N)、硝态氮(NO~-_3-N)和亚硝态氮(NO~-_2-N)与古菌amoA基因丰度均呈显著正相关关系(p0.05),而与nirS基因丰度呈显著负相关关系(p0.05).这两种功能基因明显受到花湖沉积物中不同形式氮素浓度的影响与限制.通过研究花湖沉积物氨氧化与反硝化功能基因的垂向分布特征及其对环境的响应,可为深入了解高原湖泊沉积物中的氮循环机理提供参考.

Vertical distribution and environmental response of the abundance of ammonia-oxidizing and denitrifying functional genes in sediments of Huahu Lake in Zoige

As the largest peat bog in China, the Zoige wetland is an important place for biogeochemical cycles. In this study, sediment samples at depth of 0~47 cm were collected in Huahu Lake located in the Zoige wetland. The vertical distribution of abundance of ammonia-oxidizing (amoA) and denitrifying (nirS, nirK, nosZ clade I) functional genes in sediments were explored by real-time fluorescence quantitative PCR (qPCR) technology. The mechanisms underlying their responses to environmental factors were also studied here. The results showed that the abundance of archaea-amoA gene declined with the depth, whereas the abundance of nirS gene increased. The abundance of archaea-amoA gene kept similar level as bacteria-amoA gene, but the abundance of nirS gene was much higher than that of nirK gene. Generally, the abundance of ammonia-oxidizing functional gene was 1~2 orders of magnitude lower than that of denitrifying functional gene. The abundance of archaea-amoA gene showed significant positive correlations (p<0.05) with total nitrogen (TN), total phosphorus (TP), ammonia-nitrogen (NH₄⁺-N), nitrate-nitrogen (NO₃^--N), and nitrite-nitrogen (NO₂^--N), whereas the abundance of nirS gene was significantly negatively correlated with these environmental factors (p<0.05). Therefore, the two functional genes were obviously affected and restricted by the concentration of different forms of nitrogen in sediments of Huahu Lake. It can provide reference for further understanding the nitrogen cycles in sediments of plateau lakes by studying the vertical distribution characteristics of ammonia-oxidizing and denitrifying functional genes in sediments of Huahu Lake and their responses to the environment.