Remediation of a major acid mine drainage point source discharge restores headwater connectivity for a diadromous native fish |
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Authors: | DP Gray JS Harding P Lindsay |
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Institution: | 1. School of Biological Sciences, University of Canterbury, Christchurch, New Zealand;2. Environment Group, Solid Energy New Zealand Ltd, Christchurch, New Zealand |
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Abstract: | Rivers receiving acid mine drainage (AMD) are frequently depauperate in fish and impacts may extend long distances downstream. AMD inputs may form chemical barriers for migratory species and isolate fish in unimpacted headwaters. We investigated the response of a diadromous fish, kōaro (Galaxias brevipinnis), to remediation of an AMD tributary in a 5th order river in New Zealand. A 2005 survey indicated limited recruitment of kōaro in the river likely due to the chemical barrier of AMD. By 2010, water treatment in the contaminated tributary had raised pH from a median value of 4.3 to 6 and reduced metals in the lower river, notably aluminium from a median of 2.48 to 0.41?mg/L. In 2012, kōaro density had increased by an order of magnitude relative to 2005. Furthermore, a greater proportion of juvenile fish were present. These results indicate that large-scale remediation of discharges can reverse the impacts of AMD on fish migration. |
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Keywords: | Acid mine drainage chemical migration barrier diadromous fish New Zealand water quality remediation |
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