Organic substrate availability and enzyme activity affect microbial-controlled carbon dynamics in areas disturbed by a mining dam failure

Abstract

We investigated key ecophysiological traits of microbial communities across different disturbance levels for two upper horizon depths (A1: 0–3 cm and A2: 10–13 cm) in areas disturbed by Fundão dam failure across Gualaxo do Norte river. We found that lower microbial growth (microbial biomass) and higher microbial-C losses (high qCO2) were linked to both decreases in organic substrate availability and enzyme activity suggesting important feedbacks on C dynamics in areas disturbed by Fundão dam failure. Basal respiration was not affected by organic substrate availability but increased with enzyme activity at A2 suggesting an enzymatic compensation in response to a lower plant-derived input. Lower degradative activity of extracellular enzymes (expressed as GMean index) was linked to lower organic matter content in mine tailings. Our results suggest that changes in organic substrate availability reflect changes in the microbial-controlled C dynamics in mine tailings. Thus, the design of restorative strategies based on microbial traits has the potential to accelerate the rehabilitation in areas disturbed by Fundão dam failure.