Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

Fall 2020

Thesis Director

Robert E. Colombo

Thesis Committee Member

Eloy Martinez

Thesis Committee Member

Eden L. Effert-Fanta


Midwestern United States undergo extreme temperature and precipitation fluctuations throughout the year, which leads to changing habitats within Illinois river systems. Wastewater treatment facilities have long been used to treat sewage and reduce the organic products in sewage before releasing it into aquatic environments. Wastewater treatment facilities must maintain optimal conditions, especially temperature, for reproduction and growth of facilitated bacteria that break down organic materials in wastewater. The objectives for this study were to determine the thermal effects of wastewater treatment facilities on receiving waters; and secondly, to investigate the influence of these wastewater facilities on fish abundance and assemblages. Finally, I wanted to consider physiological processes that allow individuals to adapt to extreme temperatures experienced in wastewater stream systems. In all sample streams, water temperature was warmer in the effluent habitats compared to the unimpacted habitats during the winter sampling event. Overall fish abundance was significantly influenced by the changing seasons with greater abundance in the winter. Conversely, the greatest abundances of fishes for a single site were sampled in the effluent sites during the warmest season in the two smaller order streams. Effluent discharges in these streams have a constant, flowing habitat (0.17 and 0.44 m/s) and higher dissolved oxygen concentrations (7.64 and 8.03 mg/L) that could allow for higher abundance of fishes in these sites during a period of low flow and warm temperatures. Whereas in the larger order stream, extremely high conductivity values combined with above ambient water temperatures measured in the effluent during the summer survey could have influenced the lower fish abundance. Drastic changes to water temperature, typically experienced 6 in Midwestern streams, influenced changes in the physiological thresholds, somatic indices, and population structures in a Bluegill population. The adaptative strategy to undergo physical and biochemical changes allow this shallow-dwelling species to be better suited to an environment with extreme temperatures. In warmer temperatures, Bluegill were sampled with less energy reserves indicating the allocation of resources towards growth and reproduction; however, the greater amount of energy storage seen in individuals sampled in below optimal temperatures may suggest allocation towards survival and metabolic maintenance. Upper thermal tolerance was also significantly greater in specimens sampled in warmer temperatures compared to the colder temperatures. Together this information can better explain the adaptive strategies certain populations utilize to survive seasonal changes in wastewater streams.