Effects of hexavalent chromium in rainbow trout (Salmo gairdneri) after prolonged exposure at two different pH levels
van der Putte, I.; van der Galiën, W.; Strik, J.J.
Ecotoxicology and Environmental Safety 6(3): 246-257
Toxic effects were studied in rainbow trout (Salmo gairdneri) exposed to Na2CrO4 solutions of different concentrations (0.02, 0.2, and 2.0 mg/liter Cr) and pH (7.8 and 6.5). The study involved embryo-through-juvenile and alevin-through-juvenile exposure for 32 weeks and exposure of yearling trout for 1, 3, 6, and 12 weeks. The experiments were started at the same time of the year and were carried out concurrently. When survival was used as the criterion, Cr was more toxic at pH 6.5 than at pH 7.8 in all life stages studied. For trout in the embryo-through-juvenile exposure study the lowest concentrations inducing an increase in mortality were 0.2 mg/liter Cr at pH 6.5 and 2.0 mg/liter Cr at pH 7.8. Embryo hatchability was only affected at the highest exposure concentration at a pH of 6.5. No growth retardation was detected at the termination of the experiments. In addition to survival and growth, biochemical, hematological, and histological changes were studied as indicators of toxicity in yearling trout. These parameters also showed that fish were more susceptible to Cr at the lower pH. The observed effects are discussed in relation to previously reported findings in short-term toxicity tests.