The effect of acid mine drainage on the hatching success of branchiopod egg banks from endorheic wetlands in South Africa

Abstract

Endorheic wetlands are abundant in South Africa, and are more commonly referred to as pans. The pan environment experiences daily and seasonal fluctuations in physico-chemical conditions, caused by variable hydroperiods. Branchiopod crustaceans are a unique group of fauna which are able to survive this variability through the production of dormant egg banks. The endorheic nature of these wetlands makes them more vulnerable to anthropogenic activities. A decrease in the hatching success of branchiopods could be detrimental to the biodiversity and ecosystem functioning of these wetlands. Pans were selected from regions where increasing mining activities are a potential risk. The sediment collected from selected pans was inundated with two saline solutions of 1,000 and 1,500 mg/l, respectively, which served as controls. A third solution of decanted acid mine drainage (AMD) was used to determine hatching success with exposure to AMD. Findings showed that AMD had a negative effect on the hatching success from egg banks. Recovery experiments were performed to assess whether egg banks could recover from AMD exposure upon first inundation. Recovery rates were low and support the concern that affected wetlands will suffer a loss of biodiversity.