EROD activity was determined as described by Smith
PCA of variability in biomarkers of fathead minnows in relation to sex and in mussels in relation to gravidity was performed with Torin 1 library vegan (Oksanen et al., 2015). For the fathead minnows, homoscedasticity and homogeneity were not guaranteed since both liver and gills were analyzed together.
3. Results and discussion
3.1. Water quality
Electrical conductivity of river water (SI Fig. 2) was consistently lowest at both reference sites, ranging from 329 μS/cm to 342 μS/cm. The conductivity at NSR3 at 0.15 km downstream of the discharge (580 μS/cm to 838 μS/cm) was typically double the conductivity at the reference sites. The electrical conductivity at the site 1 km downstream (NSR4) was clearly elevated, at > 500 μS/cm. At the sites 2.5 km and 9.9 km downstream (i.e. NSR5 and NSR6), electrical conductivity was still slightly elevated by approximately 20 μS/cm, relative to the reference sites.
All sites were well oxygenated, although the NSR3 site had the lowest concentrations of Dissolved Oxygen (DO), ranging from 9.5 to 10.5 mg/L. The remainder of the sites generally had DO concentrations between 11 and 12 mg/L. Since temperature has an impact on oxygen saturation, the sites were compared using %DO saturation (SI Fig. 3). All sites except NSR3 showed > 100% saturation at all times. Overall, site NSR3 had the lowest %DO saturation, but on only one occasion (i.e. between October 9 to14) was measured at < 100% saturation (approximately 97% saturation). Measurements of pH also showed differences between upstream and downstream sites. The pH at the reference sites was pH 8.5, while the pH at NSR3 and NSR4 was 7.5 and at NSR6 the pH was 8.3.