Effects of benthic animal disturbance on ammonia-oxidising microbial communities in sediments of Naoli River Wetland under varying temperatures

To investigate the effects of benthic faunal disturbance on ammonia-oxidizing microbial communities in wetland sediments under different temperature conditions, three common benthic fauna species, Chironomus plumosus, Limnodrilus hoffmeisteri, and Radix swinhoei, were selected to establish an indoor aquatic microcosm system under two temperature regimes: 22 ℃ (high temperature) and 15 ℃ (low temperature). High-throughput sequencing and real-time quantitative PCR (qPCR) were employed to compare the community structure and abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) among different treatments. The results showed that L. hoffmeisteri significantly increased total carbon (TC), total nitrogen (TN), nitrate nitrogen (NO₃⁻), and ammonium nitrogen (NH₄⁺) contents in sediments under both temperature conditions, while significantly decreasing the carbon-to-nitrogen ratio (C/N) and nitrite nitrogen (NO₂⁻) content (p<0.05). In contrast, the effects of C. plumosus and R. swinhoei on sediment physicochemical properties were relatively weak or insignificant. Significant differences in amoA gene abundance of AOA and AOB were observed among treatments, with AOA abundance generally exceeding that of AOB. Treatments with C. plumosus and L. hoffmeisteri significantly reduced AOB gene abundance, whereas R. swinhoei exerted comparatively weaker effects. Community diversity analysis demonstrated that different treatments exerted distinct effects on AOA and AOB diversity, and under high-temperature conditions, C. plumosus and L. hoffmeisteri significantly enhanced AOB community diversity. Principal coordinate analysis and community composition analysis further revealed that L. hoffmeisteri markedly altered both AOA and AOB community structures under high- and low-temperature conditions. Specifically, AOA communities were characterized by a reduction in Candidatus Nitrososphaera under both temperature conditions, whereas AOB communities showed an increased relative abundance of Nitrosomonas under high-temperature conditions. Redundancy analysis and correlation analysis indicated that TN, TC, NH₄⁺, and C/N were the major environmental factors influencing ammonia-oxidizing microbial community structure. In particular, AOB abundance was significantly positively correlated with NH₄⁺ and significantly negatively correlated with TC, TN, and NO₃⁻ (p<0.05). Overall, benthic faunal disturbance exerted significantly different effects on the community structure and abundance of ammonia-oxidizing microorganisms in wetland sediments under different temperature conditions.