Microbial communities of reclaimed mines increasingly become similar to undisturbed reference sites

Background/Question/Methods

The mining sector consistently ranks amongst the top four contributors of GDP in Canada, providing jobs to thousands of people. However, mining brings ecological damage, resulting in land degradation that impacts life at all trophic levels. As such, reclamation efforts are employed to rehabilitate the ecosystem. Traditional approaches to reclamation focus on vegetation coverage while the belowground ecology remains largely understudied. This study focuses on the impact of mine reclamation on belowground ecology – specifically the assembly of microbial community composition in reclaimed mines. This project explores the effects of a) mine reclamation strategy and b) reclamation age on microbial community assembly. To that end, we collected soil samples from a reclaimed area of an active mine (Highland Valley Copper mine). We collected samples from sites that were reclaimed either with biosolids or not. We also sampled sites along a chronosequence based on reclamation age – ranging from areas reclaimed in 1992 to 2014. For comparisons, we sampled soils from nearby references areas that were not influenced by mining activities. Further, we used high-throughput sequencing of eDNA from the collected samples. We sequenced over 125 samples targeting the 16S rRNA and the ITS gene to study bacterial and fungal communities.

Results/Conclusions

We analyzed several alpha diversity metrics (Shannon, Simpson, and richness) of bacteria and fungi and found no significant differences across reclamation strategies or age. We further examined the beta diversity of both bacterial and fungal communities and found reclamation strategy (biosolid treatments) and age were significant factors in explaining the variation associated with bacterial and fungal communities. We observed that age explained more variation than reclamation strategy indicating its importance in determining microbial community assembly. To better understand the relationship between reclamation age and microbial community, we ran linear regression against Bray-Curtis dissimilarity and reclamation age and found a significant relationship between them. We observed that the community dissimilarity of reclaimed and reference sites reduced with age. The analysis indicates that the microbial communities become increasingly similar to the reference sites as they get older regardless of the reclamation strategy. The results suggest that given enough time (several decades), the microbial community can recover from disturbances such as mining. Microbial communities play a crucial role in soil functionality; therefore, a recovery in microbial community composition may become a precursor to the rehabilitation of ecosystem function.