Mean (± SE) gammarid feeding rate. (A) Effect of exposure to different water concentrations of Zn (0, 6.6, 20, 60, and 180 µg‧L⁻¹; all n = 5). (B) Effect of exposure to different water concentrations of methomyl (MT; 0, 20, 40, 80, and 160 µg‧L⁻¹; all n = 5). (C) Effect of exposure to different water concentrations of perfluorooctanoic acid (PFOA; 0, 50, 100, 200, and 400 µg‧L⁻¹; all n = 5). *p < 0.05; **p < 0.01; ns: nonsignificant.