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Tuesday, June 5, 2007 - 8:00 AM
79
Effects of Resource Pulses and Spatial Subsidies on Food Web Dynamics and Community Structure in Karst Springs of the Ozarks
Teresa M. Carroll, Biology, Drury University, 900 N. Benton, Springfield, MO 65802 and James H. Thorp, PhD, Ecology and Evolutionary Biology, University of Kansas, 2101 Constant Avenue, Lawrence, KS 66047-3759.
Karst springs are unique freshwater ecosystems representing the dynamic interface between subterranean and epigean systems. They are characterized by hydrologically and seasonally driven organic pulses and are spatially subsidized from the source to downstream by changes in epigean-hypogean flow and riparian-stream interactions. Our study described seasonal changes in zoobenthos, food web pathways, and trophic complexity in 3 Ozark springs in response to pulsed organic inputs and spatial subsidies from the spring source downstream. To characterize food webs, we evaluated stable isotope signatures for ~20 biotic and abiotic units (terrestrial/aquatic producers, functional feeding groups, POM, DOM, DIC, and DIN) during two seasons in three spring brooks. Food web complexity and food web pathways were both significantly affected by distance from the spring source and by the amount of autochthonous production. A longitudinal gradient of species composition, richness, and evenness were evident in all springs, with non-insect fauna in the spring source rapidly decreasing in relative importance downstream as the aquatic insect composition of the spring communities increased. Basic longitudinal patterns were consistent among springs and between seasons.