Loyola University Chicago

Department of Biology

Christopher G. Peterson

Environmental Science
Ph.D. 1989, University of Louisville
Aquatic Ecology.
Phone: 773.508.2950


My research focuses on understanding how the structure, dynamics, and function of attached microalgal communities, the primary transducers of sunlight energy in aquatic systems, vary with spatial and temporal changes in chemical, physical, and biological attributes of the environment. Because of their small size and rapid turnover, algal communities within biofilms are an ideal model system for addressing general ecological questions. Within a week of biofilm development, microalgal communities can support >1 million cells/cm2 of colonization surface and contain dozens or even hundreds of species that differ widely in growth habit, resource requirements, and susceptibility to removal by physical disturbance or ingestion by grazing macro- or microinvertebrates, fish, or amphibians. Because algae are microscopic, cells residing within developing algal mats experience significant changes in the availability of light or dissolved nutrients as communities thicken; successional processes are driven by these internal changes. Community attributes at any given time are a product of the interaction between these internal factors and external factors such as the density and identity of grazers, heterogeneity in nutrient supply, variation in current regime, and the timing and magnitude of physical disturbance events.

Stream ecosystems are both spatially and temporally heterogeneous. Their nutrient content varies with land use or geology within a catchment, or the strength and pattern of hydrologic exchange between groundwater and surface water. Patterns of groundwater/surface water exchange vary over years with snowpack or volume of rainfall, which also influence the densities and identity of organisms that consume algae. Environmental variation from these and other sources influences the species composition, biomass, and physiological condition of microalgal communities. My primary goal is to equate the sensitivity of algal community attributes to environmental variation, and ultimately to assess whether variation in algal communities induced by such changes influences the ecological functioning of stream ecosystems.

I am also interested in the relevance of species identity as it relates to the broader function of biofilms in stream ecosystems. Individual algal species differ in, among other things, nutrient uptake kinetics, optimal light conditions, tolerance to gut passage through grazers, and in the molecular nature of organic carbon compounds they exude. This latter attribute influences the taxonomic composition of bacteria associated with algal cells and, in turn, may modify the efficiency with which bacteria perform metabolic reactions that control the biogeochemical cycling of elements within ecosystems. With the growing recognition of the potential importance of biodiversity in dictating environmental health, this avenue of investigation has particular relevance.


  1. Importance of algal/bacterial interactions in regulating denitrification in stream biofilms. (in collaboration with Drs. John Kelly [LUC-Biology] & Kim Gray [Northwestern Univ.])
  2. Influence of nano-titanium on the structure and function of stream communities. (in collaboration with Drs. John Kelly [LUC-Biology] & Kim Gray [Northwestern Univ.])


Peterson, C. G., A. D. Daley, S. M. Pechauer, K. N. Kalscheur, M. J. Sullivan, S. L. Kufta, M. Rojas, K. A. Gray, & J. J. Kelly (2011) Development of associations between microalgae and denitrifying bacteria in streams of contrasting anthropogenic influence. FEMS Microbiology Ecology 77: 477-592

ISHIDA, C. A., S. ARNON, C. G. PETERSON, J. J. KELLY, & K. A. GRAY (2008) Influence of algal community structure on denitrification rates in periphyton cultivated on artificial substrates. Microbial Ecology 56:140-152.

ARNON, S., C. G. PETERSON, K. A. GRAY, & A. I. PACKMAN (2007) Influence of flow conditions and system geometry on nitrate use by benthic biofilms: Implications for nutrient mitigation. Environmental Science & Technology 41:8142-8148

ARNON, S., A. I. PACKMAN, C. G. PETERSON, & K. A. GRAY. (2007) The effects of overlying flow velocity on periphyton structure and denitrification. Journal of Geophysical Research - Biogeosciences. 112: G01002.

PETERSON, C. G. (2007) The Ecology of Non-Marine Algae: Streams. Pages 434-558 In: (T. Orchard, J. Huisman, & T. Entwisle, eds.) The Algae of Australia. Australian Biological Resources Study, Canberra.

Peterson, C. G., & T. L. Jones (2003) Diatom viability in insect feces: comparison between two benthic species, Achnanthidium lanceolatum and Synedra ulna. Hydrobiologia 501:93-99.

Peterson, C. G., M. Horton, M. C. Marshall, H. M. Valett, & C. N. Dahm (2001) Spatial and temporal variation in the influence of grazing macroinvertebrates on epilithic algae in a montane stream. Archiv fur Hydrobiologie 153:29-54

Peterson C. G., H. M. Valett, & C. N. Dahm (2001) Shifts in habitat templates for lotic microalgae linked to interannual variation in snowmelt intensity. Limnology Oceanography 46:858-870.

Peterson, C. G. & A. J. Boulton. (1999) Stream permanence influences microalgae food availability to grazing tadpoles in arid-zone springs. Oecologia 118:340-352.

Peterson, C. G., K. A. Vormittag, & H. M. Valett. (1998) Ingestion and digestion of epilithic algae by larval insects in a heavily grazed montane stream. Freshwater Biology 40:1-17

Peterson, C. G. (1996) Mechanisms of lotic microalgal colonization following space-clearing disturbances acting at different spatial scales. Oikos 77:417-435

Peterson, C. G. (1996) Response of Benthic Algal Communities to Natural Physical Disturbance. Pages 375-402, In (R. J. Stevenson, M. L. Bothwell, & R. L. Lowe, editors) Algal Ecology: Freshwater Benthic Ecosystems. Academic Press, San Diego.