Assessing Microbial Diversity in Open-Pit Mining: Metabarcoding Analysis of Soil and Pit Microbiota Across Operational and Restoration Stages

Abstract

Mine closure operations aim to restore the ecosystem close to its original state. Microorganisms are key components of the soil equilibrium and therefore essential to the restoration process. We used metabarcoding techniques to characterize the bacterial and fungal composition in pristine soils, stockpiled soils (topsoils), enriched stockpiled soils (technosoils), enriched and revegetated soils (revegetated technosoils), and visually distinct pits in an open pit gold mine. Comparative analysis indicated that pristine and topsoils exhibited the highest levels of richness, followed by technosoils and pits. Taxonomic analysis identified dominant microbes’ communities. For both bacteria and fungi, the dominant genera differed between pristine/topsoils and technosoils. Ecological similarity indices showed that topsoil microbial communities were separated from pristine soil. Revegetated technosoil showed more similarity to pristine/topsoil than freshly prepared technosoil, indicating an ongoing process of microbial restoration. All pit samples differed greatly in their microbial composition, with the presence of moisture and rock composition being the main axes of dissimilarity. It is concluded that the greater community complexity in soils is related to the availability of nutrients, physicochemical variations and the possibility of interaction with other microbes, while pits could be considered as extreme ecosystems that limit the growth of most microorganisms.