蓝藻堆积对河蚬N2O释放通量及其肠道细菌群落结构的影响

Effect of cyanobacterial accumulation on the nitrous oxide emission of Corbicula fluminea and intestinal bacterial community structure

摘要:

【背景】底栖动物是湖泊生态环境的重要组成部分，在泥水界面氮迁移转化中扮演着重要的角色，是一个潜在的N2O释放源，其N2O释放量与栖息环境有关。蓝藻堆积区通常是湖泊N2O释放的热点区域，其水质环境不同于无藻区。【目的】为了解蓝藻堆积与无藻堆积时底栖动物河蚬N2O释放情况。【方法】采用室内微宇宙实验，以河蚬为研究对象，通过气相色谱和现代分子生物学相结合的技术测定蓝藻堆积区域底栖动物N2O释放特征及其内在微生物学机制。【结果】蓝藻堆积区河蚬N2O释放通量为447.2 pmol/(ind·h)，相比无藻区河蚬减少63%左右。河蚬肠道内总细菌及反硝化细菌对蓝藻堆积有不同的响应。454测序结果显示，无藻区河蚬肠道内细菌以变形菌门(β-和δ-变形菌纲)、绿弯菌门和拟杆菌门为主，三者相对丰度为67.3%，而蓝藻堆积区河蚬肠道细菌优势类群为变形菌门(α-和β-变形菌纲)，相对丰度达到85.8%。chao1和shannon指数表明，蓝藻堆积区河蚬肠道细菌丰富度和多样性低于无藻区河蚬。对河蚬肠道内具有反硝化功能细菌进一步分析发现，蓝藻堆积区河蚬肠道内反硝化菌相对丰度可达到22.6%，是无藻区河蚬的2.3倍，反硝化作用得到增强。【结论】蓝藻堆积导致河蚬肠道内细菌丰富度和多样性降低，反硝化功能菌丰度增加，完全反硝化作用得以强化，导致河蚬N2O释放通量降低。研究结果有助于揭示富营养化中湖泊底栖动物的环境效应，为湖泊温室气体控制提供理论支撑，具有重要的理论和现实意义。

Abstract:

[Background] Benthic animals are an indispensable constituent of lake eco-environment and play an important role in transformation of nitrogen between sediment and water. There have been showed that benthic animals are the potential source of N2O emission, while the release capability is closely related to habitat environment. The water quality without cyanobacterial accumulation is different from that with cyanobacterial accumulation, which is usually a hot spot of N2O emission. [Objective] To compare the N2O emission of the fresh invertebrates between with and without cyanobacterial accumulation. [Methods] Combing gas chromatography with modern molecular biology techniques, the N2O emission flux and intestinal microbial from Corbicula fluminea were analyzed to extend our knowledge about the microbiology mechanism of N2O emission through laboratory microcosm experiment. [Results] with cyanobacterial accumulation the N2O emission flux of C. fluminea was 447.2 pmol/(ind·h), decreased by about 63% in comparison with control group. The intestinal bacterial and denitrifying bacteria of C. fluminea have different responses to cyanobacterial accumulation. The 454 pyrosequencing revealed that Proteobacteria (β- and δ-), Chloroflexi and Bacteroid were dominant bacteria in control group and occupied about 67.3% of the total bacteria number. While in cyanobacterial accumulation treatment the intestinal microorganism was mainly Proteobacteria (α- and β-), and the relative abundance reached 85.8%. The index of Chao1 and Shannon indicated that the richness and diversity of intestinal bacterial community structure in cyanobacterial accumulation treatment were lower than the intestinal bacterial in control group. Further analysis was conducted on denitrifying bacteria in the intestine of C. fluminea, the result showed that the relative abundance of denitrifying bacteria in cyanobacterial accumulation treatment occupied to 22.6%, which was 2.3 times as much as the control group, thus strengthening the intestinal denitrification. [Conclusion] cyanobacterial accumulation decreased the richness and diversity of the intestine bacteria from C. fluminea, while increased the abundance of intestinal denitrifying bacteria, probably enhanced the complete denitrification, resulting in decreasing the emissions of N2O from C. fluminea. The data obtained in this study could serve as a valuable resource for the environmental effects of benthic animals, which has a great theoretical and practical significance in greenhouse-gas control.