Assistant Professor of Biology
B.S., Kent State University
Ph.D., Kent State University
- Kent State University (Zoology and Pre-medicine), B.S.
- Kent State University (Ecology), Ph.D.
- Beginning Field Biology
- Insects and Society
- Invertebrate Zoology
- First Year Seminar - The State of the World's Fisheries
Conversion of land to agriculture and urban development is occurring worldwide and has dramatic impacts on the quality of aquatic ecosystems. Impacts of agriculture and urbanization on stream health have been well-studied, however, the mechanisms driving food web dynamics and the biological community needs more attention. Furthermore, the impacts of land use change on the response of individual species (invertebrates in particular) and feeding guilds are lacking. As land use increases in the future, management of stream habitat and biological communities will become increasingly more important in order to preserve and restore stream ecosystem health. For these management practices to be effective, enhanced understanding of the mechanisms driving in-stream food webs in response to surrounding land use is essential. Future projects will focus on how changes in land use impact invertebrates (at the organismal and community level) and how changes in the invertebrate community (e.g., distribution, community structure) affect ecosystem function (e.g., rates of organic matter processing).
I am also interested in how natural abiotic and biotic parameters structure stream communities. Characterization of spatio-temporal patterns of species distribution is necessary to understand the interplay of biotic and abiotic factors influencing population dynamics, community structure, and ecosystem function. Streams, in particular, are dynamic systems having a wide range of hydraulic characteristics and geomorphology. In low-order streams, this variability often leads to a range of habitat types including pools, runs, cascades, backwaters, and riffles which, in turn, affects stream community structure. These different habitat types can be characterized by physical attributes including current velocity, substrate type, and water depth, which set limits on the species that can occupy specific habitat types. Organisms that are tolerant of a wide range of abiotic conditions (e.g., crayfish) are often influenced by habitat-specific interactions between abiotic and biotic (e.g., predation, competition) variables causing trade-offs to occur during habitat selection. Along with spatial variability, temporal considerations become important as some variables only affect organisms at certain points in their life cycle or at certain times of the year, often resulting in ontogenetic and temporal effects on habitat use. I am particularly interested in habitat-specific trade-offs and why and when they occur ontogenetically. Questions of interest to me include…What causes ontogenetic shifts in habitat use? What types of trade-offs are involved? Do trade-offs change throughout an organism’s ontogeny? How do ontogenetic habitat shifts affect stream community structure and ecosystem function?
*Hirschfeld, R. and J.M. Clark. Changes in abiotic parameters, basal resources, and the insect community in primary headwater streams along an urbanization gradient. (in preparation)
Clark, J.M. and M.T. Begley. Fight for your life: An undergraduate-level classroom game that examines optimal foraging theory. (in preparation)
Clark, J.M. and M.W. Kershner. Interactions between abiotic and biotic factors in structuring size-specific lotic crayfish distribution. (in revision for Hydrobiologia)
Clark, J.M. and M.W. Kershner. Habitat overlap and resource partitioning between a lotic fish assemblage and crayfish (Orconectes obscurus) in a forested stream. (in preparation)
Clark, J.M. and M.W. Kershner. Habitat- and size-specific temporal variation in predation risk of crayfish (Orconectes obscurus). (in preparation)
Clark, J.M. and M.W. Kershner. 2011. Short- and long-term impacts of a major flood event on crayfish (Orconectes obscurus) in a forested stream. Fundamental and Applied Limnology 179/3: 225-233.
Clark, J.M., M.W. Kershner, and J.R. Holomuzki. 2008. Grain size and sorting effects on size-dependent responses by lotic crayfish to high flows. Hydrobiologia 610: 55-66.
Clark, J.M. and M.W. Kershner. 2006. Size-dependent effects of Visible Implant Elastomer marking on crayfish (Orconectes obscurus) growth, mortality, and tag retention. Crustaceana 79: 275-284.
*indicates undergraduate co-author that I have mentored