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Summer field work

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Chemical pollution


Pinewoods treefrog (Hyla femoralis)

Research and Publications 

Pollution is considered the second greatest threat to aquatic and amphibious species (behind habitat loss) in the United States (Wilcove and Master 2005), and yet it ranked second to last out of nine threats to biodiversity in the level of research effort (Lawler et al. 2006).  Consequently, we know very little about the impact pollution has on biodiversity relative to other threats.  Further, pesticide use has been correlated with amphibian population declines (Davidson et al. 2001, 2002), suggesting that pollution might be an important factor in the declines of one of the most threatened taxa in the world.  We are making an effort to redress this gap between the threat that pollution poses and the scientific effort dedicated toward understanding the effects of pollution on biodiversity.  Here are some of the questions in which we are interested:

  • Are there general patterns in the responses of communities and ecosystems to types of pollutants, and if so, what are they?

  • Can we use community ecology theory and links between species and ecosystem functions to predict the responses of communities and ecosystems to single contaminants, as well as mixtures?

  • If a pollutant causes no direct mortality, can it still generate population declines if it alters species interactions?

  • Just how important is it to test the effects of pollutants in a community setting relative to the more traditional approach, where species are tested in the lab isolated from all other species with which they naturally coexist?

  • Do other stressors synergistically enhance the detrimental effects of pollution?

  • How does pollution affect disease risk?


Sample Publications

Rumschlag, S.L., Halstead, N.T., Hoverman, J.T., Raffel, T.R., Carrick, H.J., Hudson, P.J., Rohr, J.R. 2019. Effects of pesticides on exposure and susceptibility to parasites can be generalized to pesticide class and type in aquatic communities. Ecology Letters 22: 962-972 Cover article


Zubrod, J., Bundschuh, M., Arts, G., Imfeld, G., Knäbel, A., Payraudeau, S., Rasmussen, J., Rohr, J.R., Scharmüller, A., Smalling, K., Stehle, S., Schulz, R., Schäfer, R. 2019. Fungicides – An overlooked pesticide class? Environmental Science and Technology 53: 3347−3365


Rumschlag, S.L., Bessler, S., Rohr, J.R. 2019. Evaluating improvements to exposure estimates from fate and transport models by incorporating environmental sampling effort and national contaminant use. Water Research 156: 372-382


Rumschlag, S.L., Rohr, J.R. 2018. The influence of pesticide use on amphibian chytrid fungal infections varies with host life stage across broad spatial scales. Global Ecology and Biogeography 27: 1277-1287


Halstead, N.T., Arakala, A., Civitello, D.J., Deleo, G., Gambhir, M., Hoover, C., Johnson, S.A., Jouanard, N., McMahon, T.A., Parker, K., Raffel, T.R., Remais, J., Riveau, G., Sokolow, S., Rohr, J.R. 2018. Agrochemicals increase risk of human schistosomiasis by supporting higher densities of intermediate hosts. Nature Communications 9: 837 DOI: 10.1038/s41467-018-03189-w

         Covered in Science:


Knutie, S.A., Gabor, C., Kohl, K.D., Rohr, J.R. 2018. Do host-associated gut microbiota mediate the effect of an herbicide on disease risk in frogs? Journal of Animal Ecology 87: 489-499


Gabor, C.R., Roznik, E.A., Knutie, S.A., Rohr, J.R. 2018. Are the adverse effects of stressors on amphibians mediated by their effects on stress hormones? Oecologia 186: 393-404


Rohr, J.R. 2018. Atrazine and amphibians: A story of profits, controversy and animus. In: Dominick A. DellaSala, and Michael I. Goldstein (eds.) The Encyclopedia of the Anthropocene 5: 141-148


Rohr, J.R., Brown J., Battaglin, W.A., McMahon, T.A., Relyea, R.A. 2017. A pesticide paradox: Fungicides indirectly increase fungal infections. Ecological Applications 27: 2290-2302


Jayawardena, U.A., Rohr, J.R., Amerasinghe, P.H., Navaratne, A.N., Rajakaruna, R.S. 2017. Effects of agrochemicals on disease severity of Acanthostomum burminis infections (Digenea: Trematoda) in the Asian common toad, Duttaphrynus melanostictus. BMC Zoology 2: 13. doi: 10.1186/s40850-017-0022-1


Rohr, J.R., Salice, C.J., Nisbet, R.M. 2017. Chemical safety must extend to ecosystems. Science 356: 917


McMahon, T.A., Boughton, R.K., Martin, L.B., Rohr. J.R. 2017. Exposure to an herbicide non-linearly affected corticosterone production in tadpoles. Journal of Herpetology 51: 270-273


Burton, G.A., Di Giulio, R., Costello, D., Rohr, J.R. 2017. Slipping through the cracks:  Why is the U.S. Environmental Protection Agency not funding extramural research on chemicals in our environment? Environmental Science and Technology 51: 755-756 Featured in Science Magazine


De Laender, F., Rohr, J.R., Ashauer, R., Baird, D.J., Berger, U., Eisenhauer, N., Grimm, V., Hommen, U., Maltby, L., Meliàn, C.J., Pomati, F., Roessink, I., Radchuk, V., Van den Brink, P.J. 2016. Re-introducing environmental change drivers in biodiversity-ecosystem functioning research. Trends in Ecology and Evolution 31: 905-915


Rohr, J.R., Salice, C.J., Nisbet, R.M. 2016. The pros and cons of ecological risk assessment based on data from different levels of biological organization. Critical Reviews in Toxicology 46: 756-784


Ehrsam, M., Knutie, S.A., Rohr, J.R. 2016. The herbicide atrazine induces hyperactivity and compromises tadpole detection of predator chemical cues. Environmental Toxicology and Chemistry 35: 2239-2244


Jayawardena, U.A., Rohr, J.R., Navaratne, A.N., Amerasinghe, P.H., Rajakaruna, R.S. 2016. Combined effects of pesticides and trematode infections on the hourglass tree frog Polypedates cruciger. EcoHealth 13: 111-122


Rohr, J.R., Farag, A.M., Cadotte, M.W., Clements, W.H., Smith, J.R., Ulrich, C.P., Woods, R. 2016. Transforming ecosystems: When, where, and how to restore contaminated sites. Integrated Environmental Assessment and Management 12: 273-283

Staley, Z.R., Harwood, V.J., Rohr, J.R. in press. A synthesis of the effects of pesticides on microbial persistence in aquatic ecosystems. Critical Reviews in Toxicology

Rohr, J.R., Farag, A.M., Cadotte, M.W., Clements, W.H., Smith, J.R., Ulrich, C.P., Woods, R. in press. Transforming ecosystems: When, where, and how to restore contaminated sites. Integrated Environmental Assessment and Management


Halstead, N.T., Civitello, D.J., Rohr, J.R. 2015. Comparative toxicities of organophosphate and pyrethroid insecticides to aquatic macroarthropods. Chemosphere 135:265-271

Douglas, M.R, Rohr, J.R., Tooker, J.F. 2015. Neonicotinoid insecticide travels through a soil food chain, disrupting biocontrol of non-target pests and decreasing soybean yield. Journal of Applied Ecology 52:25-260 Editor’s Choice, cover photo, and commentary (; Altmetric score of 105, 99th percentile and top 10 ever for the journal as of 6/2015)

Staley, Z.R., Senkbeil, J.K., Rohr, J.R., Harwood, V.J. 2014. Agrochemicals indirectly increase survival of E. coliO157:H7 and indicator bacteria in freshwater by reducing ecosystem services. Ecological Applications 24:1945-1953

Boone, M.D., Bishop, C.A., Boswell, L.A., Brodman, R., Burger, J., Davidson, C., Gochfeld, M., Hoverman, J.T., Neuman-Lee, L., Propper, C.R., Relyea, R.A., Rohr, J.R., Rowe, C.L., Salice, C., Semlitsch, R.D., Sparling, D., Weir, S*. 2014. The influence of industry: how conflicts of interest compromise pesticide regulation. Bioscience 64:917-922

Halstead, N.T., McMahon, T.A., Johnson, S., Raffel, T.R., Romansic, J.M., Crumrine, P.W., Rohr, J.R. 2014. Community ecology theory predicts the effects of agrochemical mixtures on aquatic biodiversity and ecosystem properties. Ecology Letters 17:932-941

Rohr, J.R., Raffel, T.R., Halstead, N.T., McMahon, T.A., Johnson, S.A., Boughton, R.K., Martin, L.B. 2013. Early-life exposure to an herbicide has enduring effects on pathogen-induced mortality. Proceedings of the Royal Society of London 280:20131502 (Altmetric score of 71)

McMahon, T.A., Romansic, J.M., Rohr, J.R. 2013. Non-monotonic and monotonic effects of pesticides on the pathogenic fungus Batrachochytrium dendrobatidis in culture and on tadpoles. Environmental Science and Technology 47:7958-7964

Rohr, J.R., Johnson, P., Hickey, C.W., Helm, R., Fritz, A., Brasfield, S. 2013. Implications of global climate change for natural resource damage assessment, restoration, and rehabilitation. Environmental Toxicology and Chemistry 32: 93-101

McMahon, T.A., Halstead, N.T., Johnson, S., Raffel, T.R., Romansic, J.M., Crumrine, P.W., Rohr, J.R. 2012. Fungicide-induced declines of freshwater biodiversity modify ecosystem functions and services. Ecology Letters 15: 714-722

Rohr, J.R., Halstead, N.T., Raffel, T.R. † 2012. The herbicide atrazine, algae, and snail populations. Environmental Toxicology and Chemistry 31: 973-976

Jennings, D.E., Congelosi, A.M., Rohr, J.R. 2012. Insecticides reduce survival and the expression of traits associated with carnivory of carnivorous plants. Ecotoxicology 21: 569-575

Staley, Z., Rohr, J.R., Harwood, V.J. 2011. A test of direct and indirect effects of agrochemicals on the survival of fecal indicator bacteria. Applied and Environmental Microbiology 77: 8765-8774

McMahon, T., Crumrine, P., Halstead, N., Johnson, S., Raffel, T.R., Romansic, J., Rohr, J.R. 2011. Chlorothalonil: a deadly, immunomodulatory, and corticosterone-inducing fungicide to amphibians. Environmental Health Perspectives. 119: 1098-1103

Rohr, J.R., Sesterhenn, T., Stieha, C. 2011. Will climate change reduce the effects of a pesticide on amphibians?: Partitioning effects on exposure and susceptibility to pollution. Global Change Biology. 17: 657-666

Staley, Z., Rohr, J.R., Harwood, V.J. 2010. The effect of agrochemicals on indicator bacteria densities in outdoor mesocosms. Environmental Microbiology. 12: 3150-3158

Rohr, J.R., McCoy, K.A. 2010. Preserving environmental health and scientific credibility: A practical guide to reducing conflicts of interest. Conservation Letters. 3: 143-150

Martin, L.B., Hopkins, W.A., Mydlarz, L.D., Rohr, J.R. 2010. The effects of anthropogenic global change on immune functions and disease resistance. Annals of the New York Academy of Sciences: The Year in Ecology and Conservation Biology. 1195: 129-148

Rohr, J.R., McCoy, K.A. 2010. A qualitative meta-analysis reveals consistent effects of atrazine on freshwater fish and amphibians. Environmental Health Perspectives. 118: 20-32

Raffel, T.R., Sheingold, J.L., Rohr, J.R. 2009. Lack of pesticide toxicity to Echinostoma trivolvis eggs and miracidia. Journal of Parasitology. 95: 1548-1551

Clements, W.H., Rohr, J.R. 2009. Community responses to contaminants: Using basic ecological principles to predict ecotoxicological effects. Environmental Toxicology and Chemistry. 28: 1789-1800

Rohr, J.R., Schoetthofer, A.M., Raffel, T.R., Carrick, H.J., Halstead, N., Hoverman, J.T., Johnson, C.M., Johnson, L.B., Lieske, C., Piwoni, M.D., Schoff, P.K., Beasley, V.R. 2008. Agrochemicals increase trematode infections in a declining amphibian species. Nature. 455: 1235-1239

Rohr, J.R., Raffel, T.R., Sessions, S.K., Hudson, P.J. 2008. Understanding the net effects of pesticides on amphibian trematode infections. Ecological Applications. 18: 1743-1753

Leslie, T.W., Hoheisel, G.A., Biddinger, D.J., Rohr, J.R., Fleischer, S.J. 2007. Transgenes sustain epigeal biodiversity in diversified vegetable farm systems. Environmental Entomology. 36: 234-244

Rohr, J.R., Kerby, J., Sih, A. 2006. Community ecology theory as a framework for predicting contaminant effects. Trends in Ecology and Evolution. 21: 606-613

Rohr, J.R., Sager, T. Sesterhenn, T., Palmer, B.D. 2006. Exposure, post-exposure, and density-mediated effects of atrazine on amphibians: Breaking down net effects into their parts. Environmental Health Perspectives. 114: 46-50

Rohr, J.R., Crumrine, P. 2005. Effects of an herbicide and an insecticide on pond community structure and processes. Ecological Applications. 15:1135-1147

Rohr, J.R., Palmer, B.D. 2005. Aquatic herbicide exposure increases salamander desiccation risk eight months later in a terrestrial environment. Environmental Toxicology and Chemistry. 24:1253-1258

Rohr, J.R., Elskus, A.A., Shepherd, B.S., Crowley, P.H., McCarthy, T.M., Niedzwiecki, J.H., Sager, T., Sih, A., Palmer, B.D. 2004. Multiple stressors and salamanders: Effects of an herbicide, food limitation, and hydroperiod. Ecological Applications. 14:1028-1040

Rohr, J.R., Elskus, A.A., Shepherd, B.S., Crowley, P.H., McCarthy, T.M., Niedzwiecki, J.H., Sager, T., Sih, A., Palmer, B.D. 2003. The lethal and sublethal effects of atrazine, carbaryl, endosulfan, and octylphenol on the streamside salamander, Ambystoma barbouri. Environmental Toxicology and Chemistry. 22:2385-2392

Rohr, J.R., Kerby, J.L., Sesterhenn, T., Sih, A. in prep. Evidence that trait-mediated effects of pollution can cause population declines.

For a full list of publications, please see the Publications page on this website.

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