In the spring 2012, post-flotation tailings of the inactive impoundment Lintich (Slovakia) were sampled. In the impoundment sediment and also in its surrounding, we detected concentration of Pb, Zn, Cd, Cu, and Ba exceeding limiting values. We detected low values of the microbial biomass carbon and microbial activity in the impoundment sediment (LiS) and its dam (DAM) along with potential respiration stayed relatively low and therefore also substrate availability index and metabolic quotient (qCO2) were higher in the control sample (REF) than in the LiS and the DAM. The low qCO2 level indicates that microbial community, despite of dangerously high levels of heavy metals in sediment, is still able to sufficiently utilize sources of available organic carbon. Anyway, we could doubt function of the metabolic index as universal indicator of environment conditions, regarding the anthropogenic substrates. We confirmed changes in composition of the mite communities along gradient dam-impoundment. The percentage of eudominant, recendent, and subrecendent species increased at the expense of dominants and subdominants, all together with decreasing diversity and equitability of the community. We identified species Chamobates borealis, Carabodes rugosior, Metabelba propexa, and Pergalumna nervosa with negative respond under the heavy metal stress. Species Adoristes ovatus was indifferent and Dissorhina sp., Hafenrefferia gilvipes, and Oppiella nova prospered under the loaded conditions. Forty years after experimental afforestation, we expect specific community of actively surviving microorganisms and Oribatida species detected in the DAM are usual in the greatly degraded habitats or on sites in the early succession.