Reciprocal influences of temperature and copper on fathead minnows (Pimephales promelas)

Acclimation temperature had a significant effect on the lethality of copper to fathead minnows in replicated 96-hour lethality tests. Lowest median lethal copper concentrations (LC{dollar}sb{lcub}50{rcub}{dollar}) were recorded at 12 and 22{dollar}spcirc{dollar}C, with LC{dollar}sb{lcub}50{rcub}{dollar}s at 5 and 32{dollar}spcirc{dollar}C at least 140 {dollar}mu{dollar}g/l higher. This research found LC{dollar}sb{lcub}50{rcub}{dollar} copper concentrations in the 300 to 500 {dollar}mu{dollar}g/l range and a polynomial relationship between LC{dollar}sp{lcub}50{rcub}{dollar}s and acclimation temperature.; Following a 24-hour exposure to three sublethal concentrations of copper, critical thermal maxima (CTMax) were tested in minnows acclimated to four temperatures. Sublethal exposure to copper significantly decreased the CTMaxs relative to controls at three of the four temperatures. Control CTMaxs ranged from 28.6 to 40.4{dollar}spcirc{dollar}C and increased 0.46{dollar}spcirc{dollar}C for each 1{dollar}spcirc{dollar}C increase in acclimation temperature.