Elser 9725878 Ecologists have been increasingly aware of the fundamental importance of differences in the elemental composition of organisms that comprise the food webs of ecosystems. Elser, the PI on this proposal, has been one of the leaders in developing this field termed ecological stoichiometry. The work supported by this project will combine modeling investigations with experiments in field and artificial enclosures to examine the joint effects of light and nutrient availability on the organization of aquatic communities in pelagic habitats. Specifically it will test whether different light and nutrient conditions can shift pelagic communities into fundamentally different states by altering the ecological stoichiometry of dominant interactions. Modeling studies will evaluate the potential for alternate states in which one is dominated by quantity effects such as where low algal biomass limits growth by grazers and the alternate is driven by nutritional effects where poor algal food quality can limit grazer growth. Modeling results will be tested in field manipulations conducted at the Experimental Lakes Area in Canada and in artificial mesocosms at new, state-of-the-art facility at Kyoto University in Japan. Experiments will involve manipulations of light and starting grazer conditions to test predictions from the model on these alternate ecosystem states. This work will contribute to the understanding of the interface between population dynamics and ecosystem function. It has substantial theoretical and practical implications.
