Succession of fungal communities in rivers polluted by acidic mine drainage

Acid mine drainage (AMD) pollution is one of the most prominent environmental problems, causing serious damage to the surrounding environment, manifested as acidification and heavy metal pollution. The flow of AMD into the river will disrupt the ecological balance. Rivers, as vital ecological corridors connecting land, lakes and oceans, have highly complex biological and geographical environments that significantly affect the biogeographic patterns of species and various ecosystem functions. Revealing the distribution patterns and community assembly mechanisms of fungal species in AMD-polluted rivers can help clarify the ecological functions of fungi along AMD-polluted river courses and the response patterns to environmental changes. In this study, the sediment samples were collected from a tributary of the Han River, which had been chronically polluted by AMD from a pyrite mine, were analyzed by physicochemical and high-throughput sequencing to study the evolution of fungal communities in sediments of the river. The main results are as follows. During the process along the AMD-polluted river, AMD-pollution varied from severe to light pollution, returning to nearly normal habitat at the downstream river mouth (with pH increasing from 2.65 to 6.71, SO42− concentration decreasing from 3.93 g·kg−1 to 1.43 g·kg−1, DTPA-Fe concentration decreasing from 371.15 mg·kg−1 to 28.27 mg·kg−1). The diversity of fungal communities in sediments increased as the degree of AMD pollution decreased, but decreased at the river mouth where self-purification had been completed. The dominant fungal species changed from acidophile-dominated to moderately acidophilic and freshwater groups, and were replaced by a relatively homogeneous fungal community at the river mouth, with only a few genera belonging to Ascomycota and Chytridiomycota. The assembly of fungal communities in sediments was mainly driven by abiotic environmental factors such as geographical distance, pH, SO42−, DTPA-Fe and so on. This study expands the understanding of the composition and assembly mechanism of fungal communities in AMD-polluted rivers, reveals the response model of fungi to environmental changes. These findings provide new perspectives for in-situ remediation of AMD-polluted ecosystems by ecological microorganisms.