Susan Gresens



Contact Information

Smith Hall, Room No. 223


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 and European 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.

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 chironomid exuviae technique to our region.

Distribution of nuisance midge (chironomid) outbreaks in Maryland: massive emergence of chironomids from Back River is causing marina owners significant loss of business and is a periodic mess and annoyance to waterfront residents in the area.  How widespread is this problem along the Maryland Bay-front?  What environmental factors may be contributing?

Algal diversity as an indicator of eutrophication: Attached algae provide important inputs to stream food webs.  Nutrient-limitation and growth of benthic algae are affected by fine silt-clay sediments, a major source of pollution.  Such suspended sediments are capable of binding and releasing phosphorus, another major pollutant in the Chesapeake Bay watershed.  We have developed laboratory microcosms to examine the relations between algae, suspended sediments, and phosphorus, and generate predictions that can be tested in the environment.

Ecotoxicologial studies involving chironomids, e.g., Chironomus riparius and anthropogenic chemicals in laboratory microcosms.  This is dependent on collaboration with chemists who share an interest in environmental effects of the compounds they study.

Select Publications

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