Susan Gresens



Contact Info

Science Complex, Room 3101J


BS S.U.N.Y. College at Oneonta, 1980

MS University of Wisconsin, Madison 1982

PhD University of Chicago 1990

Areas of Expertise

Aquatic ecology
Chironomidae (Diptera) ecology & taxonomy


I study freshwater ecology from the perspective of benthic invertebrates and algae.  Many of my research projects involve chironomids, “non-biting midges”, as a model research system well-suited to studies of biodiversity and aquatic health. The Family Chironomidae includes thousands of species with an amazing range of ecological specialization.  Chironomid larvae are abundant in many aquatic habitats and thus are an important link in benthic food webs. On a larger geographic scale, I am using both DNA sequence data and morphological methods to compare North American, European and Asian populations of chironomid species in the genus Cricotopus, in collaboration with Dr. Torbjørn Ekrem and Dr. Elisabeth Stur, at the Norwegian University of Science and Technology, and with Dr. Xiaolong Lin at Tianjin University.  Chironomids also serve as a model system for ecotoxicological research.

Potential areas for student research:

Distribution of chironomid species along gradients of watershed urbanization: collection of floating chironomid pupal exuviae (cast pupal exoskeletons) provides an effective means to compare species diversity among streams impacted by urban development and other stressors.  Comparison of this technique with standard methods of benthic invertebrate bioassessment are

needed to adapt the exuviae technique to our region.  If you like microscopy and want to study insect biodiversity, you can gain experience in taxonomy and even assist in describing a new chironomid species.

Mosquito population dynamics: the role of egg diapause in forecasting mosquito outbreaks (graduate thesis research of Daniel McDevitt). Laboratory experiments are being conducted to determine the combination of photoperiod and temperature that induces mosquito species to lay over-wintering diapause eggs. Field work for summer and early fall 2021 will focus on mosquito trapping and monitoring in several local parks, to document the initiation of diapause egg production in natural mosquito populations. Undergraduate students will have the opportunity to assist in field monitoring or to design lab-based experiments.

Bioassessment of streams in the Red Run watershed: (graduate thesis research of Nguyen Tien Anh Quach) Current and historic responses of stream macroinvertebrate communities to urban development and stormwater mitigation in the Owings Mills watershed. A long-term data set collected by Baltimore County will be analyzed to better understand the trajectory of biotic degradation over time, and to assess the potential for restoration of this former trout stream.  Field sampling of macroinvertebrates will take place during 2021. Undergraduate students can assist with field work and laboratory processing of macroinvertebrate samples.

Select Publications

H. Cuppen, S.E. Gresens, and D. Tempelman. 2020. “Description of the larvae of Cricotopus diversus (Boesel 1983) and Cricotopus festivellus (Kieffer 1906) with keys to discrimination of larval, pupal and adult stages. (Diptera: Chironomidae). Chironomus Journal 33:4-16.

K. Bolyard, S. E. Gresens, J. D. Sivey and C.J. Salice. 2017. Are safeners safe? An assessment of the toxicity of Benoxacor, mono-chlorinated Benoxacor, S-metolachlor and a mixture to Chironomus riparius within benthic microcosms. Environmental Toxicology and Chemistry 36(10):2660-2670.

Richards-Dimitrie, T., S.E. Gresens, S. Smith, R. Seigel. 2013. Diet of Northern Map Turtles (Graptemys geographica) : Relationship to sexual dimorphism and potential impacts of an altered river system. Copeia  2013(3):477-484.

S.E. Gresens, E. Stur and T. Ekrem. 2012. Phenotypic and genetic variation within the Cricotopus sylvestris species-group (Diptera, Chironomidae), across a Nearctic- Palaearctic gradient. Fauna Norvegica 31:137-149.

Gresens, S.E. 2011. Response of Chironomidae to multiple gradients of urban impact. Proceedings of the XVIIth Symposium on Chironomidae. X. Wang (ed.) Nankai University, Tianjin, China.

Courses Taught

  • BIOL 402 General Ecology

  • BIOL 406 Limnology

  • BIOL609 Community Analysis and Bioassessment