Total and arbuscular mycorrhizal fungal communities in the first 3 years after the collapse of the Fundao Dam: are we on the ecosystem recovery pathway?

After the collapse of Fundao Dam in Mariana-MG, Brazil, the discharge of iron ore mining waste into the Doce River watershed negatively impacted the landscape. Monitoring the composition and species richness of soil microbiota may be useful bioindicators of ecosystem recovery. This study aimed to compare soil chemical properties, total fungal species, and arbuscular mycorrhizal fungi (AMF) in sites unaffected and affected by mining tailings in the first 3 years after the collapse of Fundao Dam. Soil and root samples were collected in dry and rainy seasons over 3 years in unaffected (adjacent forest and pasture) and affected areas (REC1, REC2, and PASTrec) by mine tailings. Changes in soil chemical properties over the sampling period were measured by routine chemical analyses. Total fungi in the soil was determined by high-throughput sequencing. AMF community was evaluated using spore number, root colonization, and denaturing gradient gel electrophoresis. Affected sites had higher ranges of pH and lower soil organic matter than unaffected sites. Revegetation had a positive effect on soil fungal community. Increased similarity in AMF DGGE analysis was observed in the two sampling sites over time. A high similarity of total fungi and AMF was observed between REC and pasture areas, suggesting that revegetation strategy employed may be heading towards a pasture condition. Thus, post-disturbance analysis of this study was important to evaluate of ecosystem recovery affected by the rupture of iron ore mining dam and demonstrated that the soil microbiota was a sensitive bioindicator in this long path of ecosystem recovery.