Acute effects of Cu on oxygen consumption and 96 hr-LC₅₀ values in the freshwater fish <i>Tilapia sparrmani</i> (Teleostei: Cichlidae) in Mooi River hard water, South Africa

Abstract

The median lethal copper (Cu) concentration (96 hr-LC₅₀) values for acute Cu toxicity for Tilapia sparrmanii (live mass: 30 ± 8g) in Mooi River hard water of dolomitic origin at 20° C, pH 7.9, was 68.1 µmol l^–1. At this 96 hr-LC₅₀ value the specific oxygen consumption rate (∉ O₂) decreased by 44.2 (± 2.1) % from a non-exposed value of 6.6 (± 0.32) mmol O₂ kg^–1 hr^–1 to 3.63 (± 0.23) mmol O₂ kg^–1 hr^–1. At 46.4 µmol Cu l^–1, 100% of the exposed T. sparrmanii were still alive after 96 hours, but the ∉ O₂ decreased by a mean value of 1.65 (± 0.16) mmol O₂ kg^–1 fish hr^–1 or 25% (± 2.4). Contrary to Pb and Cd, Cu as CuCl₂ 2H₂O was not precipitated in hard water four days after it was dissolved. Thus T. sparrmanii and other cichlids are shown to be more than an order of magnitude more resistant to Cu as a toxicant than most salmonids.

Keywords: acid mine drainage; acute toxicity; copper; LC₅₀ tests; metal pollution; oxygen consumption

African Journal of Aquatic Science 2006, 31(2): 305–311