| Spatial and temporal patterns of invertebrate community composition, biomass, functional diversity, foodweb dynamics, and foodweb complexity were examined in three Ozarks springs. Also examined was the effect of an experimental manipulation of algal production (function of light limitation) on foodweb pathways and complexity in one of the springs that has been intentionally deforested. Food source-consumer interactions were determined using carbon and nitrogen stable isotope and stoichiometric analyses. Isotope data were analyzed using the IsoSource, multi-food source, multi-isotope mixing model. Quantified food webs were constructed based on IsoSource predictions and biomass estimates of each consumer.Spring invertebrate community analyses indicated that biocomplexity and functional diversity increased temporally and spatially along the spring source-springbrook gradient likely due to the corresponding variability in the composition and availability of food sources. Contrary to expectations, food web analyses indicated that the trophic base of the food web was autochthonous, shifting temporally towards a greater reliance on allochthonous resources. Spatial and temporal shifts in food source availability and utilization were associated with corresponding increases in food web complexity. Isotope ratios, based on manipulation of algal production, indicated a shift toward more allochthonous-based food web pathways and increases in omnivory and food web complexity in manipulated (shaded) sites compared to open sites in the spring. The contribution of studies in spring ecosystems to overall theories of benthic invertebrate community structure and food web dynamics is, unfortunately, still limited by the paucity of descriptive and experimental studies of these ecosystems. The study began with a synthesis and conceptual evaluation of springs around the world. |
