Aquatic Sciences Meeting, Albuquerque 2001
| SS19 Revisiting Redfield: C:N:P Stoichiometry in Aquatic Ecosystems (Disciplinary Connections) |
| Date: Tuesday, February 13, 2001, Time: 2:00:00 PM |
| Location: Acoma/Zuni/Tesuque |
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| Hall, S, R, University of Chicago, Chicago, USA, srhall@uchicago.edu |
| Leibold, M, A, University of Chicago, Chicago, USA, mleibold@uchicago.edu |
| Lytle, D, A, University of Chicago, Chicago, USA, dalytle@uchicago.edu |
| Smith, V, H, University of Kansas, Lawrence, USA, valsmith@falcon.cc.ukans.edu |
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| CAN STOICHIOMETRIC CONSTRAINTS DETERMINE COMPOSITIONAL SHIFTS OF SPECIES AND THE RELATIVE IMPORTANCE OF PREDATION OVER ENVIRONMENTAL GRADIENTS? |
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| Recent advances in ecological stoichiometry have shown that gradients of stoichiometric food quality affect population dynamics of zooplankton grazers. In freshwater ecosystems, zooplankton grazers frequently encounter algal seston that does not meet their multiple resource (carbon, nitrogen, and phosphorus) demands. Are the results of elemental deficiencies of seston expressed at the community level? Furthermore, does stoichiometry constrain the relative importance of predation as a determinant of community composition? To address these questions, we factorially manipulated light, N:P ratios, and nutrient supply level to create sestonic C:N:P and productivity gradients in semi-natural pond mesocosms. To this stochiometric/productivity gradient, we applied a trophic structure treatment: autotrophs only, + grazers, and + predators (notonectids). Preliminary evidence suggests that stoichiometric gradients influenced community structure of grazers: large, efficient, and high P-demanding grazers dominated ecosystems with low sestonic C:P ratios only. Additionally, predators were more important in determining grazer composition in these ecosystems than in those with high sestonic C:P ratios. The impacts of stoichiometric gradients need to be more fully incorporated into a community-level context. |
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