CS08 Biogeochemical Cycles
Date: Monday, June 10, 2002
Time: 11:30:00 AM
Location: Saanich
 
HudsonJJ, University of Saskatchewan, Saskatoon, Canada, jeff.hudson@usask.ca
 
TESTING ALLOMETRIC THEORY: CAN PELAGIC NUTRIENT CYCLING BE ESTIMATED FROM FOOD WEB ALLOMETRY?
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Allometric theory has the potential to contribute significantly to our understanding of ecological processes in aquatic ecosystems (e.g., energy transfer, nutrient and contaminant cycling). The use of allometric models to estimate processes at the food web or ecosystem level have not been rigorously tested. For example, a pivotal component of the trophic cascade hypothesis predicts changes to nutrient cycling (turnover rate) resulting from changes in food web size structure; however, these ideas remain to be directly tested. I examined the effect of different food web size structures on planktonic phosphorus turnover in a diverse set of lakes (n>45) from the Precambrian Shield, Interior Plains and Rocky Mountains. Top consumers in these lakes were invertebrates, planktivorous fish, or piscivorous fish. Except in Precambrian Shield lakes (i.e., ELA), the size distribution of plankton was related to the type of consumer present. However, planktonic phosphorus turnover rates were invariant with plankton size distributions. This outcome suggests that nutrient cycling in pelagic food webs cannot be estimated with allometric models. Implications and explanations will be discussed.