Habitat recovery from diverted acid mine drainage pollution determined by increased biodiversity of river and estuarine benthic species

Acid mine drainage (AMD) is a frequent cause of ecological damage to many river and estuarine habitats. Once AMD pollution is halted our understanding of subsequent habitat recovery requires long-term ecological assessment. This study examines the consequences of diverting AMD away from a highly contaminated river and estuary using water quality and ecological data from pre- and post-diversion sample periods. 10-12 years following diversion, water quality and benthic macroinvertebrate biodiversity significantly improved at all sample sites of the river, indicative of ecological recovery but upstream sites that were closer to the pollution source were less improved. However, redirection of the AMD into a nearby stream channel caused an almost complete loss of benthic macroinvertebrates. Habitat recovery at the river estuary was demonstrated by increased richness of infaunal invertebrates and rocky shore species, including crustaceans, barnacles and mollusc species. Measurements of copper bioaccumulation in the barnacle Austrominius modestus showed a significant reduction in present day samples compared to those collected before AMD diversion. This study shows that within a decade, an estuarine and river system can demonstrate ecological recovery from AMD pollution, yet within this time period, recovery did not fully match uncontaminated sites.