Dr. Patricia L. Gillis

Research Scientist - Freshwater Invertebrate Ecotoxicology

Current research and/or projects

Contributing to Environment Canada’s mandate to conduct research on the impacts of contaminants on aquatic ecosystems

  • Investigate the toxicity of waterborne contaminants (metals, chloride, municipal wastewater effluents) to freshwater mussels
  • Assess the role that water quality and waterborne contaminants have in the recovery of endangered freshwater mussels

Professional activities / interests

Co-supervises graduate  students (McMaster University)

Member of Graduate Student Advisory Committees (McMaster University, University of Guelph, Trent University, Wilfrid Laurier University)

Member of the Ontario Freshwater Mussel Recovery Team

Member of the Canadian Inter-Governmental Environmental Toxicity Group

Education and awards

Post-doctoral Fellow: University of Guelph and McMaster University

Ph.D.  University of Waterloo, M.Sc. and Hon. B.Sc. University of Guelph

Key publications

Burton EA, Atkinson B, Salerno J, Khan HN, Prosser RS. Gillis PL. Lethal and sub-lethal implications of sodium chloride exposure for adult Unionid mussel species; Eurynia dilatata and Lasmigona costata. 2023. Archives of Environmental Contamination and Toxicology. 85(1):1-12. DOI:10.1007/s00244-023-01006-0


Gilroy EAM, Kleinert C, Lacaze E, Campbell SD, Verbaan S, André C, Chan K, Gillis PL, Klinck J, Gagné F, Fournier M, de Solla SR. 2023. In vitro assessment of the genotoxicity and immunotoxicity of treated and untreated municipal effluents and receiving waters in freshwater organisms. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-023-26845-1.


Waller D, Pucherelli S, Barbour M, Dahlberg A, Meulemans M, Tank S, Canniff P, Aldridge D, Claudi R, Cope G, Gillis PL, Kashian D, Mayer D, Stockton-Fiti K, Wong D. 2023. Review and development of best practices for toxicity tests with Dreissenid mussels. Environmental Toxicology and Chemistry. https://doi.org/10.1002/etc.5648


Yargeau V, Schlageter B, Alungulesa S, Gillis PL, Doran M, Hayward EE, Metcalfe CD. 2023. Integrated ozonation as a strategy for enhancing treatment of municipal wastewater in facultative sewage lagoons. Journal of Environmental Chemical Engineering 11: 209406.


Hayward EE, Gillis PL, Bennett CJ, Prosser RS, Salerno J, Liang T, Robertson S, Metcalfe CD. 2022. Freshwater mussels in an impacted watershed: Influences of pollution from point and non-point sources. Chemosphere 307: 135966.


Bauer AE, Hewitt LM, Roy JW, Parrott JL, Bartlett AJ, Gillis PL, Norwood WP, Rudy MD, Campbell SD, Rodrigues MR, Brown LR, Vanderveen R, Deeth LE, Holman E, Salerno J, Marentette JR, Lavalle C, Sullivan C, Shires K, Galicia M, Rubino J, Brown M, O’Neill A, Bickerton G, Farwell AJ, Dixon DG, Frank RA. 2022. The acute toxicity of bitumen-influenced groundwaters from the oil sands region to aquatic organisms. Science of the Total Environment 884: 157676.


Millar EN, Kidd, KA, Surette MG, Bennett CJ, Salerno J, Gillis PL. 2022. Effects of municipal wastewater effluents on the digestive gland microbiome of wild freshwater mussels (Lasmigona costata). Ecotoxicology and Environmental Safety 241: 113774.


Gillis PL, Salerno J, McKay V, Bennett CJ, Lemon KLK, Rochfort QJ, Prosser RS. 2022. Salt-laden winter runoff and freshwater mussels; assessing the effect on early life stages in the laboratory and wild mussel populations in receiving waters. Archives of Environmental Contamination and Toxicology, 82: 239–254 (Open Access).


Wang N, Kunz JL, Hardesty DK, Steevens JA, Norberg-King T, Hammer EJ, Bauer CR, Augspurger T, Dunn S, Martinez D, Barnhart MC, Murray J, Bowersox M, Roberts J, Bringolf RB, Ratajczak R, Ciparis S, Cope WG, Buczek SB, Farrar D, May L, Garton M, Gillis PL, Bennett J, Salerno J, Hester B, Lockwood R, Tarr C, McIntyre D, Wardell J. 2021 (December). Method development for a short-term 7-d toxicity test with unionid mussels. Environmental Toxicology and Chemistry, 40(12): 3392–3409.


Gillis PL, Salerno J, Bennett CJ, Kudla Y, Smith M. 2021. The relative toxicity of road salt alternatives to freshwater mussels; Examining the potential risk of eco-friendly de-icing products to sensitive aquatic species. Environmental Science and Technology-Water 1(7): 1628–1636 (Open Access).


Matten KJ, Gillis PL, Milani D, Parrott JL, Bartlett AJ, Balakrishnan VK, Prosser RS. 2021. Bioaccumulation of sediment-associated dinonylnaphthalene sulfonates in the freshwater mussel Lampsilis siliquoidea and oligochaete Tubifex tubifex. Chemosphere 264: 128391.


Matten KJ, Bartlett AJ, Milani D, Gillis PL, Parrott JL, Totio J, Balakrishnan VK, Prosser RS. 2020. The influence of organic carbon on the toxicity of sediment-associated dinonylnaphthalene sulfonic acids to the benthic invertebrates Tubifex tubifex and Hyalella azteca. Environmental Pollution 267: 115604.


Gilroy EAM, Bartlett AJ, Gillis PL, Hedges AM, Brown LR, Bendo NA, Salerno J, Holman EAM, Stock NL, de Solla SR. 2020. Toxicity of the pharmaceuticals melengestrol acetate and finasteride to benthic invertebrates. Environmental Science and Pollution Research 27: 41803-41815 (Open Access).


Matten KJ, Parrott JL, Bartlett AJ, Gillis PL, Milani D, Toito J, Balakrishnan VK, Prosser RS. 2020. Toxicity of dinonylnaphthalene sulfonates to Pimephales promelas and epibenthic invertebrates. Science of the Total Environment 741, 140260.


Osborne RK, Gillis PL, Prosser RS. 2020. Transgenerational effects of copper on a freshwater gastropod Planorbella pilsbryi. Freshwater Mollusk Biology and Conservation 23: 42–54.


Salerno J, Gillis PL, Khan H, Burton E, Deeth LE, Bennett CJ, Sibley PJ, Prosser RS. 2020. Sensitivity of larval and juvenile freshwater mussels (unionidae) to ammonia, chloride, copper, potassium, and selected binary chemical mixtures. Environmental Pollution 256: 113398.


Bartlett AJ, Hedges A, Intini K, Brown L, Maisonneuve F, Robinson S, Gillis P, de Solla S. 2019. Acute and chronic toxicity of neonicotinoid and butenolide insecticides to the freshwater amphipod, Hyalella azteca. Ecotoxicology and Environmental Safety 175: 215-223.


Roy JW, Gillis PL, Grapentine L, Bickerton G. 2019. How appropriate are Canadian Water Quality Guidelines for protecting freshwater aquatic life from toxic chemicals in naturally-discharging groundwater? Canadian Water Resources Journal 44: 205-211.


Bauer AE, Frank RA, Parrott JL, Bartlett AE, Gillis PL, Deeth LE, Rudy MD, Vanderveen R, Brown L, Campbell SD, Rodrigues MR, Farwell AJ, Hewitt, LM, Dixon DG. 2019. Toxicity of Aged Oil Sands Process-Affected Water Fractions to Aquatic Species. Science of the Total Environment 669: 702-710 (Open Access).


Salerno J, Bennett CJ, Holman E, Gillis PL, Sibley PK, Prosser RS. 2018. Sensitivity of multiple life stages of two freshwater mussel species (Unionidae) to various pesticides detected in Ontario (Canada) surface waters. Environmental Toxicology and Chemistry 37: 2871-2880.


Prosser RS, Lynn DH, Salerno J, Bennett J, Gillis PL. 2018. The facultatively parasitic ciliated protozoan, Tetrahymena glochidiophila (Lynn, 2018), causes reduction in viability of freshwater mussel glochidia. Journal of Invertebrate Pathology 157: 25-31.


Salerno J, Gillis PL, Bennett CJ, Sibley PK, Prosser RS. 2018. Investigation of clearance rate as an endpoint in toxicity testing with freshwater mussels (Unionidae). Ecotoxicology and Environmental Safety 163: 165-171.


Redman A, Parkerton T, Butler J, Letinski D, Frank R, Hewitt LM, Bartlett AJ, Gillis PL, Marentette J, Parrott JL, Hughes S, Guest R, Bekele A, Zhang K, Morandi G, Wiseman S, Giesy J. 2018. Application of the target lipid model and passive samplers to characterize the toxicity of bioavailable organics in oil sands process-affected water. Environmental Science and Technology, 52: 8039−8049.


Prosser RS, Gillis PL, Milani D, Holman EA, Ikert H, Schissler D, Toito J, Palabrica V, Parrott JL, Bartlett AJ, Balakrishnan, VK. 2018. Bioaccumulation of sediment-associated substituted phenylamine antioxidants in Tubifex tubifex and Lampsilis siliquoidea. Ecotoxicology 27: 578–589.


Jorge MB, Bianchini A, Wood CM, Gillis PL. 2018. Copper uptake, patterns of bioaccumulation and effects in glochidia (larvae) of the freshwater mussel (Lampsilis cardium). Environmental Toxicology and Chemistry 37: 1092-1103.


Bartlett AJ, Hedges AM, Intini KD, Brown LR, Maisonneuve FJ, Robinson SA, Gillis PL, de Solla SR. 2018. Lethal and sublethal toxicity of neonicotinoid and butenolide insecticides to the mayfly, Hexagenia spp. Environmental Pollution 238: 63-75.


Parrott JL, Marentette JR, Hewitt LM, McMaster ME, Gillis PL, Norwood WP, Kirk JL, Peru KM, Headley JV, Wang Z, Yang C, Frank RA. 2018. Meltwater from snow contaminated by oil sands emissions is toxic to larval fish, but not river water. Science of the Total Environment 625: 264-274.


Lynn DH, Doerder FP, Gillis PL, Prosser RS. 2018. Tetrahymena glochidiophila n. sp., a new species of Tetrahymena (Ciliophora) that causes mortality to glochidia larvae of freshwater mussels (Bivalvia). Diseases of Aquatic Organisms 127: 125-136.


Gillis PL, McInnis R, Salerno J, de Solla SR, Servos M, Leonard EM. 2017. Freshwater mussels in an urban watershed: Impacts of anthropogenic inputs and habitat alterations on populations. Science of the Total Environment 574: 671-679.


Gilroy EAM, Gillis PL, King LE, Bendo NA, Salerno JE, Giacomin M, de Solla SR. 2017. The effects of pharmaceuticals on freshwater mussels: An examination of acute and chronic endpoints of toxicity across life stages. Environmental Toxicology and Chemistry 36: 1572–1583.


Prosser RS, Bartlett AJ, Milani D, Holman EA, Ikert H, Schissler D, Toito J, Parrott JL, Gillis PL, Balakrishnan, VK. 2017. Variation in the toxicity of sediment-derived substituted phenylamine antioxidants to an epibenthic and endobenthic invertebrate species. Chemosphere 181: 250-258.


Prosser RS, Parrott JL, Galicia M, Shire K, Sullivan C, Toito J, Bartlett AJ, Milani D, Gillis PL, Balakrishnan VK. 2017. Toxicity of sediment-associated substituted phenylamine antioxidants on the early-life stages of Pimephales promelas and a characterization of effects on freshwater organisms. Environmental Toxicology and Chemistry 36: 2730-2738.


Gillis PL, McInnis R, Salerno J, de Solla SR, Servos MR, Leonard EM. 2017. Municipal wastewater treatment plant effluent-induced effects on freshwater mussel populations and the role of mussel refugia in recolonizing an extirpated reach. Environmental Pollution 225: 460-468.


Bartlett AJ, Frank RA, Gillis PL, Brown LR, Hooey T, Vanderveen R, McInnis R, Marentette JR, Hewitt LM, Brunwick P, Shang D, Headley JV, Peru KM, Parrott JL. 2017. Toxicity of naphthenic acids to invertebrates: Extracts from oil sands process-affected water versus commercial mixtures. Environmental Pollution 227: 271-279.


Prosser RS, Gillis PL, Holman EA, Schissler D, Ikert H, Toito J, Gilroy EAM, Campbell S, Bartlett AJ, Milani D, Parrott, JL, Balakrishnan, VK. 2017. Effect of substituted phenylamine antioxidants on three life stages of the freshwater mussel Lampsilis siliquoidea. Environmental Pollution 229: 281-289.


Prosser RS, Rochfort Q, McInnis R, Exall K, Gillis PL. 2017. Assessing the toxicity and risk of salt-impacted winter road runoff to the early life stages of freshwater mussels in the Canadian province of Ontario. Environmental Pollution 230: 589-597.


Prosser RS, de Solla SR, Holman EAM, Osborne R, Robinson SA, Bartlett AJ, Maisonneuve FJ, Gillis PL. 2016. Sensitivity of the early-life stages of freshwater mollusks to neonicotinoid and butenolide insecticides. Environmental Pollution 218: 428-435.


de Solla, SR, Gilroy EAM, Klinck JS, King LE, McInnis R; Struger J, Backus S, Gillis PL. 2016. Bioaccumulation of pharmaceuticals and personal care products in the unionid mussel Lasmigona costata in a river receiving wastewater effluent. Chemosphere 146: 486-496.


Nogueira LS, Bianchini A, Wood CM, Loro VL, Higgins, S, Gillis PL. 2015. Effects of sodium chloride exposure on ion regulation in larvae (glochidia) of the freshwater mussel Lampsilis fasciola. Ecotoxicology and Environmental Safety 122: 477-482.


Marentette JR, Frank RA, Bartlett AJ, Gillis PL, Hewitt LM, Peru K, Headley JV, Brunswick P, Shang D, Parrott JL. 2015. Sensitivity of Walleye (Sander vitreus) and Fathead Minnow (Pimephales promelas) early-life stages to naphthenic acid fraction components extracted from fresh oil sands process-affected waters. Environmental Pollution 207: 59-67.


Roy JW, McInnis R, Bickerton G, Gillis PL, 2015. Assessing potential toxicity of groundwater-sourced chloride discharging to an urban stream using early-life-stage freshwater mussels. Science of the Total Environment 532: 309–315.


Jasinska EJ, Goss GG, Gillis PL, Van Der Kraak GJ, Matsumoto J, Machado AA, Giacomin M, Moon TW, Massarsky A, Francois F, Servos MR, Wilson J, Sultana T, Metcalfe CD, 2015. Assessment of biomarkers for contaminants of emerging concern on aquatic organisms downstream of a municipal wastewater discharge. Science of the Total Environment 530-531: 140-153.


Marentette JR, Frank RA, Bartlett AJ, Gillis PL, Hewitt LM, Peru K, Headley JV, Brunswick P, Shang D, Parrott JL. 2015. Toxicity of naphthenic acid fraction components extracted from fresh and aged oil sands process-affected waters, and commercial naphthenic acid mixtures, to fathead minnow (Pimephales promelas) embryos. Aquatic Toxicology 164: 108–117.


Machado AA, Wood CM, Bianchini A, Gillis PL. 2014. Responses of biomarkers in wild freshwater mussels chronically exposed to complex contaminant mixtures. Ecotoxicology 23: 1345–1358.


Gillis PL, Higgins S, Jorge MB. 2014. Evidence of sub-cellular stress in wild freshwater mussel (Lasmigona costata) chronically exposed to urban-derived contaminants. Ecotoxicology and Environmental Safety 102: 62–69.


Gilroy EAM, Klinck JS, Campbell S, McInnis R, Gillis PL, de Solla SR. 2014. Toxicity and bioaccumulation of the pharmaceuticals moxifloxacin, rosuvastatin, and drospirenone to the unionid mussel Lampsilis siliquoidea. Science of the Total Environment 487: 537-544.


Gillis PL, Gagne F, McInnis R, Hooey TM, Choy EM, André C, Hoque ME, Metcalfe, C. 2014. The impact of municipal wastewater effluent on field-deployed freshwater mussels in the Grand River (ON). Environmental Toxicology and Chemistry 33: 131-143.


Blaise C, Gagné F, Gillis PL, Eullaffroy P. 2013. Polychaetes as bioindicators of water quality in the Saguenay Fjord (Quebec, Canada): a preliminary investigation. Journal of Xenobiotics. 3(s1):e1:1-2.


Giacomin MM, Bianchini A, Gillis PL, Wood CM. 2013. Interactive effects of copper and dissolved organic matter on sodium uptake, copper bioaccumulation, and oxidative stress in juvenile freshwater mussels (Lampsilis siliquoidea). Aquatic Toxicology 144–145: 105–115.


Nogueira LS, Wood CM, Gillis PL, Bianchini A. 2013. Isolation and fractionation of gill cells from freshwater (Lasmigona costata) and seawater (Mesodesma mactroides) bivalves for use in toxicological studies with copper. Cytotechnology 65: 773–783.


Jorge MB, Loro VL, Bianchini A, Wood CM, Gillis PL. 2013. Mortality, bioaccumulation and physiological responses in juvenile freshwater mussels (Lampsilis siliquoidea) chronically exposed to copper. Aquatic Toxicology 126: 137-147.


Gillis PL. 2012. Impacts of urban runoff and municipal wastewater effluents on the health of the freshwater mussel, Lasmigona costata. Science of the Total Environment 431: 348–356.


Muttray A, Reinisch C, Miller J, Ernst W, Gillis PL, Losier M, Sherry J. 2012. Haemocytic leukemia in Prince Edward Island (PEI) soft shell clam (Mya arenaria): spatial distribution in agriculturally impacted estuaries. Science of the Total Environment 424: 130–142.


Gillis PL. 2011. Assessing the toxicity of sodium chloride to the glochidia of freshwater mussels: Implications for salinization of surface waters. Environmental Pollution 159: 1702-1708.


Gillis PL, McGeer JC, Wilkie WP, Mackie GL, Ackerman JD. 2010. The effect of natural dissolved organic carbon on the sensitivity of larval freshwater mussels (glochidia) to acute copper exposure. Environmental Toxicology and Chemistry 29: 2519–2528.


Leonard EM, Pierce LM, Gillis PL, Wood CM, O’Donnell MJ. 2009. Investigations into Cadmium tolerance in Chironomus riparius: patterns of cadmium transport and sequestration. Aquatic Toxicology 92: 179–186.


Gillis PL, Wood CM. 2008. The effect of extreme waterborne cadmium exposure on the internal concentrations of cadmium, calcium, and sodium in highly tolerant Chironomus riparius larvae. Ecotoxicology and Environmental Safety 71: 56-64.


Béchard KM, Gillis PL, Wood CM. 2008. Trophic transfer of Cd from larval chironomids (Chironomus riparius) exposed via sediment or waterborne routes, to zebrafish (Danio rerio): tissue-specific and subcellular comparisons. Aquatic Toxicology 90: 310–321.


Gillis PL, Wood CM. 2008. Investigating a potential mechanism of cadmium resistance in Chironomus riparius larvae using kinetic analysis of calcium and cadmium uptake. Aquatic Toxicology 89: 180–187.


Birceanu O, Chowdhury MJ, Gillis PL, McGeer J, Wood CM, Wilkie MP. 2008. Modes of metal toxicity and impaired branchial ionoregulation in rainbow trout exposed to mixtures of Pb and Cd in soft water. Aquatic Toxicology 89: 222-231.


Béchard KM, Gillis PL, Wood CM. 2008. Acute toxicity of waterborne Cd, Cu, Pb, Ni, and Zn to first instar Chironomus riparius. Archives of Environmental Contamination and Toxicology 54: 454-459.


Gillis PL, Mitchell RJ, Schwalb AN, McNichols KA, Mackie GL, Wood CM, Ackerman JD. 2008. Sensitivity of the glochidia of freshwater mussels to copper: assessing the effect of water hardness and dissolved organic carbon on the sensitivity of endangered species. Aquatic Toxicology 88: 137-145.


Gillis PL, Reynoldson TB, Dixon DG. 2006. Metallothionein-like protein and tissue metal concentrations in invertebrates (Oligochaetes and Chironomids) collected from reference and metal contaminated field sediments. Journal of Great Lakes Research 32: 565-577.


Gillis PL, Wood CM, Ranville JF, Chow-Fraser P. 2006. Bioavailability of sediment-associated copper and zinc to Daphnia magna. Aquatic Toxicology 77: 402-411.


Gillis PL, Reynoldson TB, Dixon DG, Milani D. 2005. Assessing metal bioavailability after a mine tailings spill with metallothionein-like protein and tissue metal concentrations in T. tubifex. In Del Valls and Blasco eds. Integrated assessment of and management of the ecosystems affected by the Aznalcóllar mining spill (Spain). IOC/ICAM/UNESCO (Refereed Proceedings).


Gillis PL, Chow-Fraser P, Ranville JF, Ross PE, Wood CM. 2005. Daphnia need to be gut cleared too: The effect of exposure to and ingestion of metal-contaminated sediment on whole-body metal concentrations and the gut clearance patterns in Daphnia magna. Aquatic Toxicology 71: 143-154.


Gillis PL, Dixon DG, Borgmann U, Reynoldson TB. 2004. Uptake and depuration of cadmium, nickel and lead in laboratory exposed Tubifex tubifex and corresponding changes in the concentration of a metallothionein-like protein. Environmental Toxicology and Chemistry 23: 76-85. Best Student Paper


Gillis PL, Reynoldson TB, Dixon DG. 2004. Natural variation in a metallothionein-like protein in Tubifex tubifex in the absence of metal exposure. Ecotoxicology and Environmental Safety 58: 22-28.


Gillis PL, Diener LC, Reynoldson TB, Dixon DG. 2002. Cadmium induced production of a metallothionein-like protein in Tubifex tubifex (Oligochaeta) and Chironomus riparius (Diptera): Correlation with whole body (reproduction and growth) endpoints of toxicity. Environmental Toxicology and Chemistry 21: 1836-1844.


Gillis PL, Mackie GL. 1994. Impact of the zebra mussel, Dreissena polymorpha, on populations of Unionidae in Lake St. Clair. Canadian Journal of Zoology 72: 1260-1271.

Research facility

867 Lakeshore Rd.
Burlington, ON L7S 1A1


Adjunct Professor, Department of Biology, McMaster University

Faculty of Graduate Studies, Trent University

Faculty of Graduate Studies, University of Guelph

Faculty of Graduate Studies, Wilfrid Laurier University

Member, Society of Environmental Toxicology and Chemistry (1995-present)