Effects of emergent aquatic plants on abundance and community structure of ammonia-oxidising microorganisms

Clone library construction and quantitative polymerase chain reaction were used to investigate the effects of three emergent aquatic plant species (Iris pseudacorus, Thalia dealbata and Typha orientalis L.) on the abundances and community structures of ammonia-oxidising archaea (AOA) and bacteria (AOB). The abundances of archaeal and bacterial amoA genes ranged from 2.91 × 107 to 3.20 × 109 and 1.03 × 107 to 5.10 × 108, respectively. At the study area, T. orientalis showed the highest abundances of AOA and AOB. I. pseudacorus harbored higher AOA richness and diversity than T. orientalis, but lowest AOB abundance. Nitrososphaera, Nitrosopumilus and Nitrosotalea clusters were observed in AOA, in which the Nitrososphaera cluster was predominant. Moreover, Nitrosomonas and Nitrosospira clusters were detected in AOB, in which the Nitrosospira cluster was dominant. Assays of potential nitrification rates (PNRs) in the samples cultivated with or without ampicillin suggested that AOA may be important in nitrification in unvegetated and I. pseudacorus-associated sediments, whereas AOB may dominate nitrification in the other species.