Research Overview
Our research focuses on understanding how human activities influence aquatic ecosystems, with an emphasis on contaminants, wastewater, and cumulative environmental stressors.
Human activities within watersheds can have significant impacts on aquatic ecosystems. Environmental contaminants from urbanization, agriculture, and industrial development enter receiving waters as complex mixtures, and their combined effects are not fully understood. Aquatic communities vary in their sensitivity and resilience to natural and human-induced stressors across watershed gradients, from headwaters to downstream environments. These challenges are compounded by the continued emergence of new contaminants of concern (e.g., endocrine disruptors, nanoparticles) and rapid environmental change driven by altered land use, climate variability, and habitat degradation.
Grand River Watershed
Although our research takes us to watersheds around the world, much of our research is conducted in the local Grand River watershed, a highly impacted system influenced by urban, agricultural, and industrial activities. This system provides an ideal setting to study the effects of wastewater treatment plant effluent and other stressors on aquatic ecosystems under real-world conditions.
For over two decades, we have examined how complex contaminant mixtures affect fish health, reproduction, and community structure downstream of wastewater inputs. Our work focuses primarily on small-bodied fish such as the rainbow darter, while also including species such as greenside, fantail, and blackside darters to assess differences in sensitivity to environmental stressors.
Wastewater exposure has been shown to alter gene expression, physiology (e.g., intersex), energy allocation, and reproductive performance, leading to measurable changes in fish communities. Improvements in wastewater treatment have reduced many of these effects, demonstrating the importance of mitigation strategies and long-term monitoring in managing aquatic ecosystems.
Exposure and Biological Effects
Our research aims to understand how contaminant exposure leads to biological effects in aquatic organisms. We investigate Adverse Outcome Pathways, linking molecular responses (e.g., gene expression) to physiological changes (e.g., steroid production) and whole-organism outcomes. These relationships are evaluated through a combination of controlled laboratory studies and in situ field investigations, including caging studies where fish are deployed upstream and downstream of wastewater treatment plants to assess exposure and biological responses under real-world conditions.
Controlled exposure studies conducted in our WATER Facility allow us to evaluate the uptake, bioaccumulation, and effects of contaminants in fish under defined conditions. These experiments enable us to quantify how chemicals accumulate in tissues, assess dose-response relationships, and examine how exposure influences biological processes over time.
Field-based research is central to this work. Using electrofishing and other sampling techniques, we collect fish across diverse habitats within watersheds. We assess impacts at the individual, population, and community levels, and link observed changes to specific chemical exposures, mechanisms, and environmental stressors.
By integrating field sampling, analytical chemistry, molecular and biological tools, and modelling approaches, we aim to better predict how aquatic systems respond to complex conditions, including long-term studies in the Grand River, and other watersheds around the globe.
Fate, Transport, and Modeling
We study how natural processes within watersheds influence the fate, transport, and bioavailability of contaminants. This includes examining the factors that control contaminant partitioning and movement across environmental gradients. We work closely with collaborators in Civil and Environmental Engineering to develop and apply models (e.g., WASP) that predict organism exposure from multiple sources and conditions, and to link these exposures to ecological effects.
Environmental Management and Solutions
Our research contributes to the development of risk management and mitigation strategies aimed at reducing environmental and human health risks. In collaboration with academic, government, and industry partners, we evaluate advanced water treatment technologies (e.g., advanced oxidation, nanomaterials) and assess how infrastructure and process changes in municipal treatment plants and industrial systems influence aquatic ecosystems. These efforts aim to identify effective solutions to reduce contaminant exposure and protect freshwater environments.
Our work also includes wastewater-based surveillance approaches, where wastewater is analyzed to characterize the presence of viruses, such as SARS-CoV-2, and chemicals including drugs of abuse. These approaches provide insight into the occurrence and dynamics of contaminants within wastewater systems and support public health and environmental decision-making.
Cumulative Effects and Watershed-Scale Research
Our long-term goal is to advance cumulative effects assessment and support environmental management at the watershed scale. We investigate how multiple stressors, including contaminants, habitat alteration, and changing environmental conditions, interact to influence ecosystem health. By integrating field sampling, analytical chemistry, molecular and biological tools, and modeling approaches, we aim to better predict how aquatic systems respond to complex conditions, including long-term studies in the Grand River. This work supports the development of management frameworks that account for natural variability and the combined effects of multiple stressors on freshwater ecosystems.
Wastewater-Based Surveillance and COVID-19
In collaboration with regional partners, our research contributed to wastewater-based surveillance (WBS) efforts during the COVID-19 pandemic. By measuring viral genetic material in municipal wastewater influent, including targeted on-campus sampling at University of Waterloo residences, this approach provided a non-invasive means of tracking community-level infection trends. It enabled the detection of emerging variants and captured both symptomatic and asymptomatic cases. Our work also extended to other viral targets, including respiratory syncytial virus (RSV) and Influenza, demonstrating the broader applicability of WBS for infectious disease monitoring.
Building on this work, we are now applying WBS to analyze the presence and trends of drugs of abuse in wastewater, extending these methods to better understand patterns of substance use at the community level. Together, this research reflects our broader expertise in environmental monitoring and contaminant dynamics, and contributes to public health knowledge and response.
Nanomedicine and Cancer Therapeutics
In addition to our environmental research, our group is involved in the development and application of nanomaterials for cancer treatment. This work, that grew from our interests in nanomaterials and biosensors, is conducted in collaboration with Dr. Xu (Shine) Zhang at Cape Breton University and Dr. Runquin Jiang at the Waterloo Regional Health Network. Although distinct from our aquatic research, it reflects our broader interest in understanding how complex materials interact with biological systems and in developing innovative solutions that address challenges in both environmental and human health.
This research focuses on the use of metal-based nanoparticles, including gold, copper and hafnium nanocomposites, as platforms for enhanced therapy of cancer. Gold and hafnium nanomaterials are being explored for their ability to enhanced radiation therapy, while copper nanomaterials are being investigated for their powerful in vivo catalytic abilities. These approaches are part of a broader global effort to develop more effective and precise cancer treatments.
