现场监测结果显示水华蓝藻水华爆发时氨氮浓度偏高，其内在原因尚不清楚；结合富营养化湖泊中“沉降蓝藻促进底泥-水界面反硝化作用”的研究成果，本申请项目提出“沉降蓝藻可能促进底泥-水界面微生物的DNRA作用，并从自身DNRA过程中获取能量以维持存活”这一科学假说。本申请项目将利用稳定氮同位素示踪技术，围绕上述假说开展实验室模拟研究和现场围隔研究，解析由蓝藻引起的底泥-水界面氮素变化和对微生物DNRA过程的驱动作用，以及在暗光缺氧条件下蓝藻的存活与DNRA过程的相关性，相关研究成果将有助于拓展对蓝藻驱动的湖泊生态系统氮素迁移转化过程的认识和理解，并为揭示沉降蓝藻存活提供新的科学解释。

Field monitoring results show concentration of NH4+-N is higher when the algal bloom outbreak; however, its mechanism is not clear. Recently investigations have illustrated that in eutrophic lake sinking cyanobacteria would promote the denitrification in water-sediment interface. According to it, the proposal puts a hypothesis that sinking cyanobacteria would promote the DNRA of microorganism in water-sediment interface，and obtain energy to maintain the survival from its own DNRA. In this proposal, we intend to conduct field mesocosm study and laboratory simulation experiment combined with 15N isotope-tracing technique to investigate the effects of cyanobacteria on the changes of nitrogen in water-sediment interface and the DNRA of microorganism, and the relationship between the survival of cyanobacteria and its own DNRA in the dark and anoxic conditions. The results would help to expand nitrogen migration and transformation process in lake ecosystem driving by cyanobacteria, and provide new scientific explanation for revealing the survival of cyanobacteria.