Effects of Wastewater Treatment Effluent on Fish Communities in an Illinois River Tributary

As a consequence of human activities, wastewater treatment effluent has the potential to alter the water quality of rivers. Periods of drought allow wastewater to make up the majority of a river’s compositions downstream of the effluent discharge. The Sangamon River is impounded in Decatur, IL, and receives effluent from the Sanitary District of Decatur approximately four miles downstream. We assessed fish communities using electrofishing gear upstream and downstream of the effluent in 2013 and 2015. Additionally, we assessed water quality parameters monthly, including dissolved oxygen, pH, temperature, conductivity, alkalinity, hardness, total nitrates, and total phosphates.  River discharge was recorded monthly. Shifts in relative abundances of families were observed in both upstream and downstream reaches between 2013 and 2015. Water quality differed between reaches and years, with river discharge being the largest cause of variance. These results indicate water quality in the Sangamon River is impacted by effluent discharge during periods of low river discharge, as well as by temporal variations, and may impact fish communities. Research in 2016, including the evaluation of sex ratios, blood vitellogenin levels in male fish, and presence of testicular oocytes in several species, will further determine the effects of effluent discharge.