Algal assemblage responses to acid mine drainage and steel plant wastewater effluent up and downstream of pre and post wetland rehabilitation

Abstract Algae give a time-integrated indication of specific water quality components and respond rapidly to water quality changes making them useful for biomonitoring purposes. Freshwater algae were employed to differentiate between water quality conditions up and downstream before and after wetland rehabilitation to determine the feasibility of wetland enlargement as a possible rehabilitation measure. Grootspruit valley bottom wetland, impacted by acid mine drainage, was severely degraded before restoration. Rehabilitation was done through redirection of water flow using concrete structures to enlarge the surface area by 9.4 ha. After wetland rehabilitation, pH values, suspended chlorophyll- a and alkalinity concentrations increased downstream, while electrical conductivity, sulphate, total suspended solids decreased up to 80%. Algae species diversity and richness corresponded with the improvement of water quality and also increased downstream after rehabilitation. Overall, results indicated an improvement in algal diversity and water quality after enlargement of the bottom wetland.