Biotic and abiotic determinants of intermediate-consumer trophic diversity in the Florida everglades

Authors

Brooke L. Sargeant, Department of Biological Sciences and the Southeast Environmental Research Center, Florida International UniversityFollow
Evelyn E. Gaiser, Department of Biological Sciences and the Southeast Environmental Research Center, Florida International UniversityFollow
Joel C. Trexler, Department of Biological Sciences and the Southeast Environmental Research Center, Florida International UniversityFollow

Abstract

Food-web structure can shape population dynamics and ecosystem functioning and stability. We investigated the structure of a food-web fragment consisting of dominant intermediate consumers (fishes and crayfishes) in the Florida Everglades, using stable isotope analysis to quantify trophic diversity along gradients of primary production (periphyton), disturbance (marsh drying) and intermediate-consumer density (a possible indicator of competition). We predicted that trophic diversity would increase with resource availability and decrease after disturbance, and that competition could result in greater trophic diversity by favouring resource partitioning. Total trophic diversity, measured by niche area, decreased with periphyton biomass and an ordination axis representing several bluegreen algae species. Consumers’ basal resource diversity, estimated by δ¹³C values, was similarly related to algal community structure. The range of trophic levels (δ¹⁵N range) increased with time since the most recent drying and reflooding event, but decreased with intermediate-consumer density, and was positively related to the ordination axis reflecting increases in green algae and decreases in filamentous bluegreen algae. Our findings suggest that algal quality, independent of quantity, influences food-web structure and demonstrate an indirect role of nutrient enrichment mediated by its effects on periphyton palatability and biomass. These results reveal potential mechanisms for anthropogenic effects on Everglades communities.

Comments

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Recommended Citation

Sargeant, B., E.E. Gaiser, J.C. Trexler. 2010. Biotic and Abiotic Determinants of Intermediate-Consumer Trophic Diversity in the Florida Everglades. Marine & Freshwater Research 61: 11-22.