Spatiotemporal evolution and assembly processes of ammonia-oxidizing prokaryotic communities in 1000 years of coastal reclaimed soils

Abstract

Coastal marshes are transitional areas between terrestrial and aquatic ecosystems and are sensitive to climate change and anthropogenic activities. In recent decades, the reclamation of coastal marshes has greatly increased, and its effects on microbial communities in coastal marshes have been studied with great interest. However, most of these studies have explained short-term spatiotemporal variation in soil microbial community dynamics. Besides, the impact of reclamation on functional microbial community composition and assembly processes is often ignored. Therefore, community structure and assembly processes of ammonia-oxidizing prokaryotes in long-term reclaimed coastal marshes have not been studied. In the current study, using qPCR and IonS5™XL sequencing platform, we investigated the spatiotemporal dynamics, assembly processes, and diversity patterns of ammonia-oxidizing prokaryotes in 1000-year-old reclaimed coastal salt marshes. The taxonomic and phylogenetic diversity and composition of ammonia oxidizers showed apparent spatiotemporal variations along with the reclamation of the soil. The phylogenetic null modelling-based analysis showed across all sites, the archaeal ammonia-oxidizing community was assembled by a deterministic process (84.71%), while stochastic processes dominated in the ammonia-oxidizing bacterial assemblage at stage 60 years (|βNTI| < 2), despite the relatively dominant deterministic process (55.2%). The assembly process and nitrification activity in reclaimed soils were positively correlated. An abundance of the amoA gene and changes in ammonia-oxidizing archaea (AOA) and bacteria (AOB) diversity significantly affect nitrification activity in reclaimed soils. These findings suggest that long-term coastal salt marsh reclamation affects nitrification by modulating the activities of ammonia-oxidizing microorganisms and regulating their community structures and assembly processes. These results provide a better understanding of the effects of long-term land reclamation on soil nitrogen-cycling microbial communities.