Inside old reclaimed mine tailings in Northern Ontario, Canada: A microbial perspective

Abstract

Large areas of metal–contaminated tailings have been revegetated in Northern Ontario (Canada). The specific objective of the present study is to determine if variations in vegetation, and soil physico-chemistry in sulfide tailings is associated with microbial biomass, abundance and diversity. Microbial biomass was determined using Phospholipid fatty acid analysis (PLFA). Amplicon based analysis of the soil bacterial and fungal microbiota was assessed by high throughput sequencing of 16S rRNA gene for bacteria and internal transcribed spacer (ITS) region for fungi. Significant differences in soil pH, organic matter content, and total metals (Cu, Fe, Ni, and Zn) were observed among sites. There were significant variations in microbial biomass among the tailing sites with areas covered with white birch showing the highest level of bacterial and fungal biomass compared to areas vegetated by pines species or pine-white birch mixture. Proteobacteria was the most dominant bacterial phylum while Basidiomycota was the predominant fungal phylum. The most abundant bacterial genus was Mucilaginibacter , followed by Acidobacterium , Acidisphaera , Burkholderia , and Steroidobacter . Site-specific bacterial and fungal genera were identified. However, there were no significant differences for # of OTUs, Chao 1, Simpson index, Shannon index, and species richness among the bacterial populations from different soil tailing areas despite differences in plant populations and soil physico-chemistry. The relative abundance of fungi was associated with the variation in ecology of specific areas. Chao 1, # of OTUs, Simpson index, Shannon index, and species richess were significantly lower at Vale 3 compared to Vale 1 and Vale 5.