Insights on the response of microbial communities to vegetation and biogeochemical properties in amended and unamended acid-generating mine wastes

Understanding the structure of microbial
communities in acidic, metal contaminated tailings and waste rock in cool,
continental northern temperate climates is important for identifying their potential
for use in phytostabilization and bioremediation programs. In this study, microbial
community compositions across two large mine waste sites in the Sudbury basin were
analyzed along gradients of barren-to-vegetated tailings and waste rock. Microbial
communities were less diverse, more homogenous, and mainly chemolithoautotrophic
in barren sites, transitioning to more diverse communities of organoheterotrophs,
nitrogen-fixing/plant-growth promoting bacteria, and ectomycorrhizal fungi in
the vegetated areas. Network interaction analyses of microbial communities demonstrated
higher levels of interactions of microbial groups in the barren tailings, which
were related to the extreme environmental and chemical conditions and
restricted anabolic nutrient availability of the substrates. We also show that
vegetation and plant-derived organic matter in the tailings are associated with
the shifts observed in the structure of microbial communities towards more soil-like
communities, which sequentially further aids in the establishment of
vegetation. These
findings have implications for the optimization of phytoestablishment and bioremediation
in mine tailings and waste rock in the cool, continental northern temperate and boreal climates.