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DEVELOPMENT OF A STREAM FOOD WEB MODEL CONSTRAINED BY STABLE ISOTOPE DATA
Citation:
Eldridge, P M. AND S. T. Larned. DEVELOPMENT OF A STREAM FOOD WEB MODEL CONSTRAINED BY STABLE ISOTOPE DATA. Presented at North American Benthological Society, Vancouver, British Columbia, June 6-10, 2004.
Description:
Traditional stream food web studies provide static models of trophic structures. These models provide information about interspecific relationships, but not about material flows through food webs. Traditional ecosystem models developed from budgets or tracers provide quantitative estimates of material flows, but are hampered by low resolution among food web components, and do not account for species interactions. Combining trophic structures with biogeochemical fluxes and physiological data can generate detailed, quantified food web models. Constructing such models for natural streams will be challenging due to high trophic diversity and large flows between the stream and adjacent ecosystems. The number of potential material flows will generally exceed the number of measured flows, so many different models of the food web are possible. To identify the most realistic (or simplest) model, the values of flows must be constrained, and an optimization procedure employed. Inverse analysis is such a procedure. Here we discuss the use of inverse analysis in aquatic food web analysis, and describe a method for constraining flows using stable isotope data. We use examples from several ecosystems to illustrate the utility of the method, and its strengths and weaknesses. In particular we will explore the sensitivity of these models to natural and anthropogenic nutrient inputs.