9528840 Threlkeld Plant and animal communities are often influenced by material flows or organism movements from adjacent habitats, although the extent of influence on neighboring communities is poorly known. In aquatic systems, these neighborhood influences are mediated through water circulation, sedimentation, resuspension, or the life history movements of key consumer or prey species. Although the size frequency distribution of organisms in natural communities has been used to understand trophic interactions in individual communities, the proposed research will investigate the extent to which size structure changes in adjacent habitats are related to each other, which might suggest important inter-habitat linkages. The proposed research will use a 28-pond experiment to examine the link between communities in bottom and open water habitats by evaluating if experimentally-induced changes in size structure in one habitat result in similar or complementary community size structure changes in the adjacent habitat. A broad array of nutrient and consumer treatment combinations known to influence size distributions of biomass and particulate phosphorus in one of the two habitats will be used to measure how communities in adjacent habitats are linked. Because heterogeneity is common in the spatial arrangement of habitats, it follows that processes organizing the community of one habitat may influence those of adjacent habitats, even beyond edge effects which are often present and well documented. The proposed pond experiment is the first aquatic study to evaluate directly if and to what extent size structure changes in one habitat are related to those in adjacent habitats, providing evidence of community linkage in aquatic systems and a means for evaluating landscape level patterns in other systems.
