Sean McLay

Sean completed his undergraduate degree at the University of Waterloo, where his interest in aquatic ecology developed through Dr. Mark Servos’ BIOL 470 course. This experience helped shape his focus on applied environmental monitoring and the effects of wastewater on aquatic ecosystems.

He later completed his MSc research under the co-supervision of Dr. Adam Yates, examining the ecological effects of upgrades to the Kitchener and Waterloo wastewater treatment plants on the central Grand River. His work used benthic macroinvertebrate (BMI) assemblages as bioindicators to evaluate changes in receiving water quality in a system undergoing major wastewater infrastructure improvements.

Using long-term monitoring data collected upstream and downstream of effluent outfalls between 2009 and 2018, Sean assessed changes in macroinvertebrate community structure associated with treatment plant upgrades. His analyses included multivariate approaches to evaluate overall assemblage shifts, as well as univariate metrics such as family richness. He also incorporated comparisons across additional wastewater treatment plants within the Region of Waterloo, along with independent sampling sites along the central Grand River.

The results showed increasing similarity between upstream and downstream benthic macroinvertebrate assemblages at the Waterloo and Kitchener facilities following upgrades, reflected in reduced Bray-Curtis dissimilarity and improved downstream biological condition. These patterns suggest a reduction in effluent-related ecological stress and indicate ongoing ecosystem recovery, although full recovery may still be developing due to the timing of recent upgrades and known lag times in benthic community response.

Overall, this research highlights the value of benthic macroinvertebrates as indicators of wastewater treatment performance and reinforces the importance of long-term monitoring frameworks, such as BACI designs, for distinguishing anthropogenic impacts from natural environmental variability.