Steven L. Kohler
Environmental Studies
Program and
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 Glossosoma’s effects (and those of other biotic
processes) on community structure is being explored in a suite of systems
(Michigan’s Lower Peninsula, Michigan’s 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.
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.
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.