长江三峡大坝两侧水体中氨氧化微生物种群结构分析

Structure of planktonic ammonia-oxidizing community in the waters near the Three Gorges Dam of the Yangtze River

【目的】研究自然界中的氨氧化微生物对于理解全球氮元素循环至关重要,而人们对于人工坝体对氨氧化微生物种群生态的影响还知之甚少。本工作旨在分析三峡大坝两侧水体中浮游和附着在颗粒表面的氨氧化微生物种群构成的多样性,并试图分析其潜在的控制因素。【方法】在靠近三峡坝体的上游水体及下游水体中各选取1个取样点,在取样点现场测量水体理化参数并收集生物量,采用氨氧化功能基因的mRNA逆转录产物构建克隆文库等技术分析样品中氨氧化微生物种群的多样性。【结果】坝下水体中浊度、溶氧量和氧化还原电位略高于坝上水体。坝体两侧的氨氧化菌以氨氧化古菌(AOA)为主,没有检测到氨氧化细菌(AOB)。坝体两侧水体不同存在方式的AOA组群存在差异:坝上水体中附着在颗粒表面的AOA多样性较高,而坝下水体中浮游的AOA多样性更高;坝上水体中附着在颗粒表面与浮游的AOA种群间的差异明显大于坝下水体。【结论】三峡大坝对坝体两侧水体中AOA种群主体构成的影响不是很明显,但三峡大坝产生的水动力条件改变影响了坝体两侧水体中浮游和附着在颗粒表面的AOA组群分布。

[Objective]Investigation of ammonia-oxidizing microorganisms （AOM） in natural environments is of great importance to understand global nitrogen cycling.However,little is known about the effects of dam constructions on the AOM community.We studied the diversity of the free-living and particle-attached AOM populations in the waters behind and in front of the Three Gorges Dam of the Yangtze River,and analyzed the possible correlation between the observed difference in the two fractions of AOM with the environmental parameters.[Methods]Two sampling locations near the Three Gorges Dam were selected：one behind and the other in front of the dam.Physicochemical profiles of waters at each location were measured,and the biomass in the waters was collected by filtration.The diversity of AOM in the collected samples was investigated by using an integrated approach including reverse transcription and clone library construction.[Results]The turbidity,dissolved oxygen,and redox potential of the water in front of the dam were higher than those behind the dam.The AOM population behind and in front of the dam was dominated by ammonia-oxidizing archaea,whereas the ammonia-oxidizing bacteria were not detected.The distribution of free-living and particle-attached AOA behind and in front of the dam was different：the particle-attached AOA behind the dam was more diverse than that in front of the dam,whereas the free-living AOA showed the opposite tendency;the difference between the fractions of AOA behind the dam was apparently higher than that in front of the dam.[Conclusion]The dominant AOA population did not show significant variation in the waters behind and in front of the dam,whereas the altered water dynamics resulted from the TGD construction may change the distribution of free-living and particle-attached AOA fractions in the waters behind and in front of the dam.