Prior to all statistical analyses diatom abundance data were

Statistical analyses were conducted with R version 3.0.2 (R Development Core Team, 2013) using packages MASS (Venables and Ripley, 2002) and vegan (Oksanen et al., 2013). Additionally, the diatom species counts were entered into Omnidia 5.5 software (Lecointe et al., 1993) for the calculation of IPS values. We used this index, as it was developed to evaluate overall water quality in terms of organic pollution and nutrient levels (Coste in CEMAGREF, 1982).