Analysis of the Phylogenetic and Functional Dynamics of Microbial Communities in Metalliferous, Acid-Generating Mine Tailings Subject to a Phytostabilization Treatment

Abstract

Extensive research conducted over the last decade has demonstrated the great potential of phytostabilization for the reclamation of abandoned mine tailing piles. The right combination of plant species and soil amendments can facilitate the growth of a permanent vegetative cover on the tailings that will help minimize the mobilization of metal-bearing particles by means of wind dispersion and water erosion. Despite previous research efforts, the diversity and potential role of microbial populations inhabiting the root zone of the plants on the stabilization of the metal(loid) contaminants remains mostly unresolved. The study presented in this dissertation represents one of the first comprehensive efforts aimed to understand the ecology and dynamics of microbial communities colonizing both bulk and rhizosphere tailings during phytostabilization as an initial step towards elucidating the role of microbes in the stabilization of metal(loid) contaminants during the remediation treatment. This study was divided into two main projects: (1) the first aimed to monitor the temporal variations in functional and taxonomic diversity of prokaryotic populations in acid-generating metalliferous mine tailings during phytostabilization to determine how they respond to and/or influence changes in environmental parameters and to identify key patterns in their composition that may serve as bioindicators of soil health and the success of the remediation treatment; and (2) the second aimed to expand our understanding of the dynamics of root-associated bacterial, fungal and archaeal communities during mine tailing phytostabilization and how the dynamic behavior of the communities correspond to the growth of plants, the addition of soil amendments, and fluctuations in environmental conditions. The results presented here demonstrate that different microbial groups respond differently to changes in environmental conditions during phytostabilization, suggesting that by monitoring the behavior of specific microbial groups in the systems (as bioindicators) we may be able to assess the effectiveness of the remediation treatment. Furthermore, the results from the taxonomic and functional analysis of the microbial communities served as the basis for the development of a model that explains the ecology and distribution of dominant microbial groups in the tailings that may significantly contribute to the oxidation of iron-sulfides, the production of acid mine drainage, and to facilitate plant establishment and survival during phytostabilization.