Acid Mine Drainage Index (AMDI): A benthic invertebrate biotic index for assessing coal mining impacts in New Zealand streams

Abstract

Acid mine drainage (AMD) is a widespread phenomenon globally. Drainage into streams from coal mines often contains a cocktail of acidic waters high in dissolved metals, and consequently stream invertebrate communities may be severely impacted. Traditionally, the intensity of impacts has been assessed by combinations of water chemistry and benthic invertebrate metrics; however, a metric specifically designed for assessing mining impacts has not been developed. We propose a benthic invertebrate biotic index: the Acid Mine Drainage Index (AMDI), based on species presence data. The AMDI has been developed by associating water chemistry and benthic invertebrate community data collected from 91 sites. AMD indicator scores for 57 taxa were calculated using weighted averaging. Site scores can range from 0 (severely impacted) to 100 (unimpacted) and sites can be categorised as severely impacted, impacted or unimpacted. Comparisons between AMDI and traditional indices indicated the AMDI is more accurate at detecting mine drainage. © 2012 The Royal Society of New Zealand.