Fig. 1. SOD activity (Unit/mg p.) in the liver ofO. niloticus following exposure to Cr
and Pb (1 mg/mL) for 0, 1, 7 and 14 days. Data are expressed as mean
(n¼6)7standard deviations. Significant differences (Po0.05) resulted from the
Duncan tests between tap water controls and salinity controls (fish were exposed
to different salinities only) were shown with ‘‘#’’ while the differences between
salinity controls and salinityþmetal combination exposures were shown with ‘‘n’’.