Microbial diversity patterns and extracellular enzyme activities of river sediment in different geomorphic regions of the Loess Plateau

Abstract

Geomorphic zoning can change soil physicochemistry, and the sediment formed by soil erosion contains various types of microorganisms. In this study, samples were collected from the aeolian sand and loess regions in the Wuding river basin on the Loess Plateau to determine sediment enzyme activities and microbial communities. The environmental pollution in the aeolian sand region was worse than that in the loess region. The activities of carbon and nitrogen cycling enzyme were higher in the loess region. Electric conductivity and ammonia nitrogen in runoff were significantly correlated with carbon cycling enzyme activity. Nitrogen cycling enzyme activity was significantly correlated with temperature and total phosphorus in runoff. The bacterial communities in the aeolian sand region had higher alpha diversity index, and the values of Simpson, Shannon, and Chao1 indices were 0.98, 8.17, and 2087.95, respectively. Conversely, alpha diversity index of the fungal communities in the loess region was higher, and the values of Simpson, Shannon, and Chao1 indices were 0.92, 5.99, and 424.19, respectively. Proteobacteria and Ascomycota were the dominant phyla in the microbial community. In the aeolian sand region, silt in sediment was the most significant influencing factor for bacterial community changes, while ammonia nitrogen in runoff was the most notable for fungal community changes. In contrast, electric conductivity in runoff emerged as the most significant factor affecting the changes of both bacterial and fungal communities in the loess region. This study offered new insights into the distribution of enzyme activities and microbial communities within river sediment across various geomorphic regions, contributing to understanding of the formation of sediment microbial communities on the Loess Plateau.