人类活动对三峡消落带土壤亚硝酸盐型甲烷厌氧氧化菌群落的影响

由"Candidatus Methylomirabilis oxyfera(M.oxyfera)"主导的亚硝酸盐型甲烷厌氧氧化过程(nitrite-dependent anaerobic methane-oxidizing,ndamo)是碳循环中新发现的一个过程.已有研究发现三峡库区消落带有n-damo菌的存在.为了解人类活动对n-damo菌群落结构的影响,对三峡库区受人类活动干扰程度不同的消落带n-damo菌群落进行了研究.结果表明,人为干扰水平高的小河消落带n-damo菌基因丰度(8.98×102~3.31×105copies·g~(-1))整体上要高于白家溪(4.72×102~5.32×104copies·g~(-1)).此外,淹水都会导致两个地点n-damo菌基因丰度的增加.白家溪的n-damo菌丰度与累积淹水时间呈线性正相关,而小河的n-damo菌丰度与土壤总氮显著负相关.系统发育树和多样性分析表明,淹水前白家溪和小河相近高程土壤n-damo菌群落结构比较类似,但淹水后出现较大差异;较低高程土壤的群落多样性要明显高于较高高程土壤.消落带土壤中的n-damo菌群落具有明显的时空异质性,且淹水会导致这种异质性增加.淹水和人类活动对于n-damo菌的多样性具有同等的重要性.这些结果表明,淹水和人类活动都会影响消落带土壤中n-damo菌群落结构,而人类活动可能进一步增加n-damo菌的丰度和多样性.

Influences of anthropogenic disturbance on nitrite-dependent anaerobic methane-oxidizing bacterial community in water level fluctuation zone of the Three Gorges Reservoir

Nitrite-dependent anaerobic methane-oxidizing (n-damo) mediated by "Candidatus Methylomirabilis oxyfera (M. oxyfera)" is a recently discovered process in carbon cycle. The presence of n-damo bacteria in the water level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) was reported previously. In order to understand the influence of human activities on the n-damo bacteria, the n-damo bacterial community from two WLFZs in the TGR with contrast anthropogenic disturbance was investigated. The results showed that the gene abundance of n-damo bacteria in the site of Xiaohe (8.98×10² to 3.31×10⁵ copies·g^-1), which has high level of anthropogenic disturbance, was generally higher than that of Baijiaxi (4.72×10² to 5.32×10⁴ copies·g^-1). Besides, the gene abundance increased after water flooding in both sites. A linear positive correlation was observed between the abundance and accumulate flooding time in Baijiaxi. Whereas the abundance in Xiaohe showed a significant negative correlation with the total nitrogen. Phylogenetic and diversity analyses showed that the community structure of n-damo bacteria was similar in parallel elevations of the two sites before flooding, but greater differences were observed after flooding. The community diversity of n-damo bacteria in soils of low elevations were higher than that of higher elevations. The community structure of n-damo bacteria in WLFZ showed obvious spatial-temporal heterogeneity, and the heterogeneity was further increased by water flooding. These results suggest that the water flooding and human activities are of equal importance in influencing the n-damo bacterial community diversity. Overall, both the water flooding and human activities could affect the n-damo bacterial community in WLFZ, and the human activities have the effect of increasing the abundance and diversity.