Research Goals
Aquatic ecosystems serve as “sinks” for contaminants which can impact drinking water quality, fisheries, and other important ecosystem services. The main themes of my research are Contaminants of Emerging Concern, New Approaches to Legacy Pollutants, and Chemical Stressors in Complex Aquatic Environments. Contaminants of emerging concern (CECs) are newly identified and unregulated contaminants that may be harmful to wildlife and human health. CEC research is important for informing risk assessments, policy, and new regulations. By contrast, legacy pollutants are regulated contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), that continue to persist in the environment and can be released through landfill leachate, dredging, improper disposal, or oil spills. New, innovative research is needed to address persistent challenges with legacy pollutants. In addition to contaminants, aquatic organisms are also exposed to environmental stressors such as pathogens, temperature, pH, nutritional status, salinity, and hypoxia (low oxygen). Many of these stressors are increasing due to climate change and can exacerbate the impacts of contaminant exposure.
My research goals are to 1) determine the combined effects of chemicals and climate change stressors on aquatic organisms, 2) characterize the sources, transport, fate, and effects of emerging contaminants in the Great Lakes, and 3) develop innovative solutions for freshwater oil spill toxicity, response, and preparedness. To address these research goals, I use both field and laboratory approaches including field surveys, in situ and multiple stressor exposures, multi-omics techniques, and sub-organismal to whole organism assessments (e.g., cytotoxicity, metabolic rate, development, and behavior). Together, this research can inform innovative solutions and policies for addressing contaminants in aquatic ecosystems.
PFAS sampling in Great Lakes wetlands
Using drones to track oil slicks
Oil slick work
PFAS sampling in Great Lakes wetlands
Research Projects
PFAS in Great Lakes Ecosystems
PFAS are synthetic chemicals used in a wide range of industrial and commercial applications such as non-stick coatings, waterproofing, metal plating, and firefighting foams. Once in the environment, PFAS break down very slowly and can infiltrate water systems and bioaccumulate within food webs. We quantified PFAS in surface water, sediment pore water, plankton, and fish at a PFAS-contaminated wetland near Lake Huron. We determined that PFAS originating from a nearby military base was widely distributed in these environmental matrices and was accumulating in biota (Leads et al., in preparation). Using field mesocosms, we also characterized the impacts of environmental PFAS exposure on fish growth and reproduction. In laboratory experiments, we determined that PFAS exposure can adversely affect growth and survival of Great Lakes fishes. This work is ongoing in Dr. Cheryl Murphy's laboratory in the Department of Fisheries and Wildlife and Center for PFAS Research at Michigan State University. In 2025, we received a two-year grant from the US Geological Survey (USGS) Water Resources Research Act Program to determine the impacts of PFAS exposure on neurotoxicity and microbiome health in Great Lakes fish.
Oil Spills and Photo-Induced Toxicity
Oil spills can release large quantities of PAHs into aquatic ecosystems and be widely dispersed by winds and currents. We characterized the impacts of oil spills on marine and freshwater organisms and determined how toxicity can be influenced by ultraviolet (UV) radiation (Leads et al., 2022), dissolved organic carbon (Bonatesta et al., 2020), and chemical dispersants (Leads et al., in review). Using zebrafish, we identified new information about the mechanisms of oil toxicity in developing fish, which targets the neurological and cardiovascular systems (Leads et al., in review; Magnuson et al., 2023). UV radiation from sunlight can significantly increase the toxicity of oil to aquatic organisms through photo-induced toxicity. This is critical to consider in ecosystems that receive high levels of sunlight and/or are experiencing reduced ice cover and increased UV exposure due to climate change. We determined that photo-induced toxicity can damage tissues, impair growth, and alter the development of sensory systems such as the eyes and otoliths (inner ear structures) in early life stage fish (Leads et al., in preparation). This can impact important processes for survival and recruitment such as respiration, osmoregulation, prey capture, and predator avoidance. We also determined that toxicity can be further exacerbated by the use of chemical dispersants (surfactants to break up oil slicks) during oil spill response. To collect real-time toxicity and water quality data, we developed a novel oil spill response technology called the In situ Mobile Platform for Aquatic Contaminant Testing (IMPACT) which can be rapidly deployed in contaminated surface waters (Leads et al., in preparation). This research was conducted at the University of North Texas with Dr. Aaron Roberts.
Microplastics in Coastal Ecosystems
Microplastics are small (<5 mm) particles from plastic pollution that can bioaccumulate and exert toxicity in wildlife and humans. In Charleston, SC, we completed a large regional survey in the Charleston Harbor watershed to identify microplastic sources, riverine transport, and fate in the estuary (Leads and Weinstein, 2019; Gray et al., 2018). We discovered that tire wear particles produced from the abrasion of tires on roads were a major source of pollution throughout the estuary. Tire wear particles can contain heavy metals and contaminants such as PAHs and 6PPD. These findings were featured in the 2019 National Geographic article “Tires: The plastic polluter you never thought about.” We also determined that environmental factors such as wind, waves, tides, and precipitation greatly influence the breakdown, distribution, and abundance of microplastics in coastal ecosystems (Leads et al., 2023; Weinstein et al., 2020). In addition to being ubiquitous in water and sediment, microplastics and tire wear particles were also present in Eastern oysters and grass shrimp we collected throughout the estuary (Leads et al., in preparation). This has important implications for food web bioaccumulation and human dietary exposure. We then characterized the acute toxicity of microplastics and tire wear particles to grass shrimp and determined how exposure can impact susceptibility to Vibrio infection (Leads et al., 2019). This is critical to consider as climate change is expected to increase the prevalence and severity of aquatic pathogens. This research was conducted at the College of Charleston and The Citadel with Dr. John Weinstein.