Effect of acclimation period on the relationship of acute copper toxicity to water hardness for fathead minnows

Abstract

Abstract-The acute (96-h) toxicity of copper sulfate to fathead minnows was tested in a 2 ϫ 2 factorial experiment, with factors being low (ca. 1 meq/L) and high (ca. 4 meq/L) water hardness during an acclimation period and low and high hardness during the exposure period. Acclimation hardness was found to have no significant effects on copper lethality, except that the 24-h LC50 at high exposure hardness was 44% higher for fish subject to low acclimation hardness than fish subject to high acclimation hardness. In contrast, exposure hardness was found to have major effects, with LC50s being two to three times greater at high exposure hardness than at low, regardless of the acclimation hardness. These results suggest that the extent of the acclimation period is not a general, severely confounding factor for previous reports of the effects of hardness on copper toxicity to fish, although it may assume some importance for some species and test conditions.

Effect of culture water hardness on the sensitivity of Ceriodaphnia dubia to copper toxicity

“…Barron and Albeke [17] reported a similar response with zinc, where acclimation to high‐hardness (348 mg/L as CaCO 3 ) waters reduced zinc uptake by RBT compared to those cultured at a lower hardness (43 mg/L as CaCO 3 ). In studies with fathead minnows, Erickson et al [5] reported no significant differences in 96‐h LC50s due to acclimation conditions, although LC50s were slightly higher for organisms acclimated in the higher‐hardness water (215 vs 47 mg/L hardness as CaCO 3 ). On the other hand, studies by Welsh et al [10] showed that RBT were more tolerant to copper in hard water (hardness of 180 mg/L as CaCO 3 ) when they were acclimated for two weeks in softer waters (88 mg/L as CaCO 3 ).…”

“…Many water quality parameters have been shown to affect copper toxicity to aquatic organisms, including water hardness, alkalinity, sodium, pH, and dissolved organic carbon [1–4]. Of these factors, the water hardness in which organisms were exposed is one of the more important factors affecting sensitivity to copper [2,5,6]. Not only will the total hardness of a water influence copper toxicity, but the relative ratio of the individual ions that make up hardness (Ca 2+ and Mg 2+ ) can also alter copper toxicity to some species [7,8].…”

“…And in fact, Lloyd [9] and Welsh et al [10] observed that acclimating rainbow trout to test waters altered their sensitivity to zinc and copper, respectively. However, this phenomenon was not observed with fathead minnows ( Pimephales promelas ) [5].…”