Steven L. Kohler

Environmental Studies Program and

Department of Biological Sciences

Western Michigan University

 

Research Interests

 

My research focuses on the nature of interactions among species and the consequences of these interactions for the dynamics of populations and the structure of communities.These questions are addressed with experimental and observational approaches over a broad range of temporal and spatial scales, using trout streams as a model system.Specific areas of research include:

 

1)The roles of species interactions and disturbance in affecting the structure and resilience of stream communities.Recent work has utilized stream-wide manipulations of a strong interactor (the periphyton-grazing caddisfly Glossosoma nigrior) by outbreaks of a host-specific pathogen as a tool to identify mechanisms affecting community structure and the resilience of coldwater stream communities to major perturbations in food web structure.I collaborate with Dr. Mike Wiley, the University of Michigan, on this research.We also use the results of these manipulations in statistical (structural equation modeling) and analytical models to develop testable hypotheses about the roles of other species in affecting food web structure.In addition to the whole-stream manipulations, we use smaller scale field and laboratory experiments to determine how interactions involving Glossosoma shape community structure and to identify the effects of other species.The role of disturbance in modifying Glossosomaís effects (and those of other biotic processes) on community structure is being explored in a suite of systems (Michiganís Lower Peninsula, Michiganís western Upper Peninsula, mountains of western Maine) representing a broad gradient in hydrologic disturbance regimes.

 

2)The importance of disease in the population and community ecology of aquatic invertebrates.Obligate pathogens, many of which invariably kill their hosts, are common in aquatic invertebrates.We are addressing a broad array of questions, from basic biology (e.g., determining the life cycle of important pathogens) to whether pathogen infections are important in affecting the population dynamics of their hosts.

 

3)The foraging behavior of aquatic invertebrates.Research has focused on how several aspects of foraging behavior (e.g., search behavior within and among habitats, timing and rates of foraging activity) are affected by predation risk and food availability.Of special interest has been the examination of such effects in a community context.

 

4)Processes affecting the structure and integrity of stream communities from local to watershed scales.I initiated an ongoing, long-term study in four Illinois drainage basins addressing the effects of land use manipulations (implementation of best management practices) on stream quality in relatively small (< 150 km2) watersheds.I have broad interests in how stream communities respond to both environmental perturbations and restoration activities.

 

Selected Recent Publications

 

Steinmetz, J., S. L. Kohler, and D. A. Soluk.2003.Birds are overlooked top predators in aquatic food webs.Ecology 84:1324-1328.

 

Cassidy, D., D. Hampton, and S. Kohler. 2002. Combined chemical (ozone) and biological treatment of polychlorinated biphenyls (PCBs) adsorbed to sediments.Journal of Chemical Technology and Biotechnology 77:663-670.

 

Kohler, S. L., and W. K. Hoiland.2001.Population regulation in an aquatic insect: the role of disease.Ecology 82:2294-2305.

 

Heilveil, J. S., S. L. Kohler, and L. F. Solter. 2001. Studies on the life cycle and transmission of Cougourdella sp., a microsporidian parasite of Glossosoma nigrior (Trichoptera: Glossosomatidae). Great Lakes Entomologist 34:9-15.

 

Kohler, S. L., D. Corti, M. C. Slamecka, and D. W. Schneider.1999.Prairie floodplain ponds: mechanisms affecting invertebrate community structure.In D. Batzer, R. B. Rader, and S. A. Wissinger, editors.Invertebrates in freshwater wetlands of North America: ecology and management.John Wiley and Sons, New York, New York, USA.

 

Kohler, S. L. and M. J. Wiley.1997.Pathogen outbreaks reveal large-scale effects of competition in stream communities.Ecology 78:2164-2176.

 

Wiley, M. J., S. L. Kohler, and P. W. Seelbach.1997.Reconciling landscape and local views of aquatic communities: lessons from Michigan trout streams.Freshwater Biology 37:133-148.

 

Corti, D., S. L. Kohler, and R. E. Sparks.1997.Effects of hydroperiod and predation on a Mississippi River floodplain invertebrate community.Oecologia 109:154-165.

 

Current Graduate Student Projects

 

Jeff Steinmetz (University of Illinois, Ph.D)

Effects of avian predators on stream fish assemblages

 

Julie Ryan (Western Michigan University, M.S.)

Sublethal effects of disease in an aquatic host-microparasite system

 

Stephanie Swart (Western Michigan University, M.S.)

Interactive effects of environmental stress and disease on the performance of stream invertebrates.