Impacts of wastewater treatment plant effluent on energetics and stress response of rainbow darter (Etheostoma caeruleum) in the Grand River watershed

Abstract

The objective of this study was to assess the effects of municipal wastewater treatment plant effluent on the energetics and stress response of rainbow darter (Etheostoma caeruleum). Male and female rainbow darter were collected upstream and downstream of the Waterloo WWTP in the Grand River watershed, ON, Canada. To assess the effects of wastewater treatment plant effluent on whole-body and tissue specific metabolic capacity, closed-chamber respirometry and muscle-enzyme activity analyses were performed. Plasma cortisol was also collected from fish before and after an acute air-exposure stressor to evaluate the cortisol stress response in fish exposed to additional stressors. Male and female rainbow darter collected downstream of the effluent had higher oxygen consumption rates, while differences in enzyme activities were primarily associated with sex rather than collection site. No impairment in the cortisol stress response between downstream and upstream fish was observed, however baseline cortisol levels in female fish from the downstream site were significantly higher compared to other baseline groups. Stress-induced cortisol levels were also higher in female fish from both sites when compared to their male counterparts. Overall, this study demonstrates that chronic exposure to WWTP effluent impacts whole-body metabolic performance. This study was also able to demonstrate that sex-differences are a key determinant of various metabolic changes in response to physiological stress, thereby, providing a novel avenue to be considered and further explored.

Multiple Stressors in the Environment: The Effects of Exposure to an Antidepressant (Venlafaxine) and Increased Temperature on Zebrafish Metabolism

“…Our results also indicate that VFX and temperature may be working cumulatively, as RMR was highest in the multi-stressed group. This is in line with other studies that have demonstrated the effects of various contaminants on metabolic rate, such as polychlorinated biphenyls, metals (McGeer et al, 2000), metals (Rajotte and Couture, 2002), and wastewater effluent (Du et al, 2018, 2019; Mehdi et al, 2018). At the tissue level, we demonstrated elevation in muscle glucose levels in the multi-stressed group compared to the Control , and increased PK activity in both Temp and VFX & Temp relative to Control and VFX .…”

“…1.11.1.6). Enzyme assays were performed following the protocols described in Mehdi et al (2018). For reference, enzyme activities were also measured at assay temperatures matching both exposure temperatures (27–32°C), data shown in Supplementary Materials (Supplementary Figure 1).…”

“…However, despite the relatively low concentrations of these chemicals, their impact on aquatic organisms can be significant and has become a source of growing concern. This partly stems from the biochemical nature of these chemicals, as they have the ability to alter the physiological and behavioral responses of exposed aquatic organisms due to the highly conserved drug targets and physiological pathways across vertebrates (Arnold et al, 2014; Brown et al, 2014; Margiotta-Casaluci et al, 2014; McCallum et al, 2017; Mehdi et al, 2018; Saaristo et al, 2018). Another concern of these chemicals that is relatively unexplored is their frequent presence with other stressors, especially in environments impacted by wastewater inputs.…”

“…Metabolic physiology is an important indicator and contributor to fitness as it is linked to various levels of biological organization. Previous studies have demonstrated that exposure to WWTP effluent poses additional metabolic costs demonstrated by elevation in oxygen consumption rates (Du et al, 2018, 2019; Mehdi et al, 2018). VFX, at environmentally relevant concentrations, has also been shown to potentially act as a metabolic disruptor in fish when exposed to secondary stressors (Best et al, 2014).…”

The effect of tertiary treated wastewater on fish growth and health: Laboratory-scale experiment with Poecilia reticulata (guppy)

“…Study done in natural water bodies receiving treated wastewater and containing estrogens, revealed seasonal changes in the HSI, but these did not correlate to plasma vitellogenin concentrations [73], supporting the assumption that elevated vitellogenesis in the liver caused by exposure to estrogenic factors is not the only cause for changes in HSI. Elevated HSI in fish may indicate stress response to TWW exposure and the different contaminants it contains (estrogenic and non-estrogenic), resulting in elevated hepatic lipid content and altered activity, such as gluconeogenesis and glycolysis [74,75].…”