Abstract
Historic and modern tailings piles and waste dumps in east Otago (South Island) and the Coromandel Peninsula (North Island) of New Zealand encompass a wide range of physico‐chemical environmental conditions, and host chemolitho(auto)trophs (iron‐ and sulfur‐oxidising bacteria, IOB and SOB respectively) and sulfate‐reducing bacteria (SRB). Sulfide mineral grains are only marginally altered, even after up to 100 years of surficial exposure, at all sites examined. The environmental parameters of the tailings piles and waste rock dumps were examined to determine their effect on the growth of these bacterial isolates. This study revealed the co‐occurrence (at the cm scale) of IOB, SOB, and SRB in many of these environments, supporting previous findings from acidic sites and extending the spectrum to circumneutral‐to‐alkaline anoxic spoils. The apparently unweathered appearance of sulfide grains supports the idea that sulfate reduction dominates over sulfur oxidation in these environments. Temperature, rainfall, and dissolved metal(loid) concentrations appear to have little effect on the bacterial populations. These results indicate that the environmental parameters investigated have very little bearing on the presence of IOB, SOB, and SRB in the tailings piles and waste rock dumps examined in this study.