Fig. 2

Relative hepatic EROD activity [%] in rainbow trout exposed up- and downstream of different WWTPs. Frequencies are given relative to respective control levels. Latter were set to 100%. Bold lines within boxes display the median values, boxes the 25–75% quantiles, whiskers the minimum and maximum values, circles potential outliers. Sample sizes: a WWTP A: upstream: n = 15 and downstream: n = 17; b WWTP B: upstream: n = 16 and downstream: n = 15. c WWTP C: prior to WWTP upgrade: upstream: n = 17 and downstream: n = 11, subsequent to WWTP upgrade: upstream: n = 38 and downstream: n = 41. Asterisks and horizontal lines indicate significant differences between exposure sites; asterisks within boxes indicate significant differences to the respective controls. a WWTP A: ANOVA(sqrt), F(2,40) = 0.61, p = 0.5490. b WWTP B: ANOVA(sqrt), F(2,56) = 5.64, p = 0.0059; Tukey HSD: upstream vs. control: p = 0.0142; downstream vs. control: p = 0.0394. c WWTP C: prior to upgrade: ANOVA(sqrt), F(2,35) = 10.06, p = 0.0004, α′ = 0.0250/upstream vs. control: pairwise comparison, p = 0.0490, α′ = 0.0500, downstream vs. control: pairwise comparison, p = 0.0001, α′ = 0.0125 and upstream vs. downstream: pairwise comparison, p = 0.0061, α′ = 0.0250. Upstream/prior vs. subsequent to WWTP upgrade: ANOVA(sqrt), F(1,53) = 17.31, p = 0.0001, α′ = 0.0170. Downstream/prior vs. subsequent to WWTP upgrade: ANOVA(sqrt), F(1,50) = 44.57; p < 0.0001, α′ = 0.0100