Heavy Metals: Confounding Factors in the Response of New Zealand Freshwater Fish Assemblages to Natural and Anthropogenic Acidity


Acidification of freshwaters is a global phenomenon, occurring both through natural leaching of organic acids and through human activities from industrial emissions and mining. The West Coast of the South Island, New Zealand, has both naturally acidic and acid mine drainage (AMD) streams enabling us to investigate the response of fish communities to a gradient of acidity in the presence and absence of additional stressors such as elevated concentrations of heavy metals. We surveyed a total of 42 streams ranging from highly acidic (pH 3.1) and high in heavy metals (10mgL-1 Fe; 38mgL-1 Al) to circum-neutral (pH 8.1) and low in metals (0.02mgL-1 Fe; 0.05mgL-1 Al). Marked differences in pH and metal tolerances were observed among the 15 species that we recorded. Five Galaxias species, Anguilla dieffenbachii and Anguilla australis were found in more acidic waters (pH < 5), while bluegill bullies (Gobiomorphus hubbsi) and torrentfish (Cheimarrichthys fosteri) were least tolerant of low pH (minimum pH 6.2 and 5.5, respectively). Surprisingly, the strongest physicochemical predictor of fish diversity, density and biomass was dissolved metal concentrations (Fe, Al, Zn, Mn and Ni) rather than pH. No fish were detected in streams with dissolved metal concentrations > 2.7mgL-1 and nine taxa were only found in streams with metal concentrations < 1mgL-1. The importance of heavy metals as critical drivers of fish communities has not been previously reported in New Zealand, although the mechanism of the metal effects warrants further study. Our findings indicate that any remediation of AMD streams which seeks to enable fish recolonisation should aim to improve water quality by raising pH above ≈ 4.5 and reducing concentrations of dissolved Al and Fe to < 1.0mgL-1.


Biological Sciences


Foundation for Research, Science and Technology of New Zealand


This project was funded by the New Zealand Foundation for Research, Science and Technology (contract CRLX0401).

Keywords and Phrases

Acid Mine Drainage; Acidic Water; AMD; Dissolved Metal Concentrations; Elevated Concentrations; Fish Communities; Fresh Water; Freshwater Fishes; Human Activities; Local Adaptation; Metal Concentrations; Metal Tolerance; Multiple Stressors; Natural Leaching; New Zealand; South Island, New Zealand; Trace Metals; West Coast; Aluminum; Concentration (Process); Dissolution; Fish; Heavy Metals; Industrial Emissions; Leaching; Manganese; Manganese Compounds; Metals; Organic Acids; Toxicity; Trace Analysis; Water Pollution; Water Quality; Zinc; Trace Elements; Aluminum; Iron; Nickel; Water Pollutant; Acidification; Acidity; Community Response; Freshwater; Industrial Emission; PH; Pollution Tolerance; Remediation; Acidification; Anguilla Australis; Anguilla Dieffenbachii; Biomass; Cheimarrichthys Fosteri; Community Structure; Concentration (Parameters); Concentration Response; Controlled Study; Density Gradient; Eel; Environmental Impact Assessment; Freshwater Environment; Galaxias; Gobiomorphus Hubbsi; Nonhuman; PH Measurement; Physical Chemistry; Sensitivity Analysis; Species Difference; Species Diversity; Water Contamination; Analysis; Animal; Epidemiology; Water Pollutant; Acids; Animals; Confounding Factors (Epidemiology); Hydrogen-Ion Concentration; Metals, Heavy; Water Pollutants, Chemical; South Island; West Coast [South Island]; Lepomis Macrochirus; Philypnodon

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Article - Journal

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© 2010 Elsevier, All rights reserved.

Publication Date

01 Jul 2010

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