attached algae exposed to paraquat with concentrations ranging from 0.0276 to 0.276 mg/l synthesized less chlorophyll a and c than the control group that encountered 0 mg/l of paraquat. (The data represented a statistical significance of P < 0.01.) Regarding those exposed to paraquat concentrations of more than 2.76 mg/l, their biomass was adversely affected. In other words, the synthesis of attached algae was inhibited