| dc.description.abstract | The Grand River watershed extends throughout the majority of Southern Ontario with its
final outlet at Lake Erie and accommodates thirty wastewater treatment plants (WWTP) with
varying types and degrees of treatment. Many WWTPs are currently unable to effectively
eliminate several contaminants of concern (CECs) from their final effluent, leading to measurable
concentrations in surface waters and ultimately chronically exposing aquatic species to mixtures
of CECs. Exposures to CECs have reported impacts on oxidative stress, measurable through
reactive oxygen species (ROS) and the antioxidant defense response which helps reduce the
toxicity of ROS generated molecules. This thesis aims to investigate the effects of WWTP effluent
on four Etheostoma (Darter) species endemic to the Grand River. Objectives were to examine if
increased antioxidative response markers are present in the brains of darters downstream from the
effluent outfall compared to clean reference site upstream relative to the Waterloo, ON WWTP
between two separate years (Fall 2020 and Fall 2021). This was assessed using transcriptional
analysis and enzymatic analysis of antioxidant enzymes (SOD, GPX, CAT) and an enzyme
involved in serotonin synthesis (TPH). In fall 2020, significant differences in transcript expression
of markers were found among sites and sexes in greenside darters (GSD) with SOD and CAT
showing increased expression downstream. Changes in transcript expression aligned with
antioxidative enzyme activity where interactive effects with sex-related differences were observed
in fish collected the Fall of 2020. In contrast, transcription markers measured in Fall 2021 were
increased upstream compared to species below the effluent outfall.
Field research is essential to understand subtle effects of wastewater effluent on non-target
species, meaning a species that is not intentionally targeted by CECs. Using in vitro studies to
supplement in vivo studies provide a better understanding in the mechanisms for any observed
phenotypic response. Therefore, this thesis also aimed to investigate the mechanism in alterations
in antioxidant response by exposing isolated brain primary cell culture collected from zebrafish
and darters to environmentally relevant concentrations of venlafaxine. Antioxidant response of the
cells was assessed through cell viability, and antioxidant enzyme activity. Antioxidant enzyme
activity of SOD and CAT were both increased in zebrafish, RBD, and GSD isolated brain cultures
exposed to 0.01-1 ug/L of venlafaxine. This response supplements the observed changes in
antioxidant response of darters in the Grand River as they are chronically exposed to contaminated
effluent containing notably high concentrations of pharmaceuticals.
Overall, this thesis demonstrates how yearly varying abiotic factors such as observed
temperature increases in Fall 2021, species-specific differences, sex-differences, and venlafaxine
have roles in increased antioxidant response observed in non-target species. Continued
investigation on the impacts of pharmaceutical exposures in non-target organisms is crucial to
further the knowledge of WWTP effluent impacts. | en |
