Oligotrophic wetlands of the Florida Everglades support very high biomass of basal resources in the form of periphyton, but relatively low biomass of macroinvertebrates and fish and an increasing number of exotic species. The relative contrition of basal energy sources from autotrophic (green) and heterotrophic-detrital inputs (brown) to consumer production is an important question for management and restoration decisions because food webs with a combination of green and brown sources may be more stable. We used a dataset of carbon and nitrogen stable isotopes gathered from cyanobacteria, benthic flocculent organic matter, periphyton mats, aquatic vegetation (11 species), aquatic invertebrates (11 species), and fishes (19 species) during the late 1990s in tandem with stomach content data collected at the same time to evaluate food web basal resources in the Everglades. Stomach content data were used to determine source groups for isotope mixing models.
Results/Conclusions
Based on our mixing models, consumers were classified as green, brown, or yellow (consumers receiving energy from a mixture of brown and green sources) based on the relative contribution by green and brown sources. Out of the 30 consumers in this study two were brown, 19 were yellow, and 9 were green. Most consumers use energy originating from detrital sources emphasizing the importance of detritus in this food web. Future work will use this study to provide a historical base condition against which to compare the present food web that includes recent non-native additions to the fish community.