Project Summary Sheet

Project: Network Analysis of Trophic Dynamics in South Florida Ecosystems

Web Sites: ATLSS.ORG; http://www.cbl.umces.edu/~atlss

Location (Subregions & Counties): Greater Everglades

Funding (Source): USGS Place-Based Studies

Principal Investigator(s): Robert E. Ulanowicz, University of Maryland, Chesapeake Biological Laboratory, Solomons, MD 20688-0038, Phone: 410-326-7266, e-mail: ulan@cbl.umces.edu

Project Personnel: Donald L. DeAngelis, Phone: 305-284-1690, e-mail: ddeangelis@umiami.ir.miami.edu; Johanna J. Heymans, Michael Ignotovich, Cristina Bondavalli

Supporting Organizations: USGS/BRD, NPS, ACE, EPA, Univ. MD Center Environmental Science

Associated Projects: Component of ATLSS Program

Overview & Status: A set of networks of trophic exchanges, detailing who eats whom and at what rates, was compiled for each of the four major biomes of South Florida — the cypress wetlands, the mangrove estuaries, Florida Bay and the graminoid wetlands. In addition to serving as calibration tools for other ATLSS models, the process of assembling the networks itself reveals numerous interesting aspects of how these ecosystems are functioning, including the following. (1) The primary resource for the higher fauna of the cypress wetlands is production by understory vegetation. (2) The diet of the American alligator is instrumental in maintaining the biodiversity of wetland fauna. (3) The cypress, mangrove and especially the graminoid wetlands all sequester significant amounts of carbon on an annual basis. (4) Algal periphyton usually contributes more directly to sustaining animal life in the graminoid wetlands and Florida Bay than does macrophytic vegetation. (5) Ecological activity in the graminoid wetlands is significantly higher on a per- unit- area basis than that of the cypress and mangrove wetlands or of Florida Bay. Data collection and analysis essentially completed. See website for full results. Networks are ready to be applied as "calibration data" for ATLSS simulation runs.

Needs & Products: Perhaps the most significant finding of this project has been the confirmation of the fact that the cypress, mangrove and especially the graminoid wetlands all sequester significant amounts of carbon on an annual basis. Secondarily, this study helped to revise some long- standing conceptions about how these wetland ecosystems were functioning. The conventional wisdom has long been that these are detrital-based ecosystems. That is, that the higher organisms are supported primarily via dead macrophytes that were in turn devoured by small animals called detritivores, which formed the basis of the predatory food chain. As a result of the first year of study, it was discovered that the primary resource for the higher fauna of the cypress wetlands is not the detrital litterfall, but rather production by understory vegetation. Furthermore, algal periphyton usually contributes more directly to sustaining animal life in the graminoid wetlands and Florida Bay than does macrophytic vegetation. The project also showed that the diet of the American alligator is instrumental in maintaining the biodiversity of wetland fauna. That is, without the alligator and its control of the snake and turtle populations, about a dozen species would probably be considerably depressed below current levels. Finally, the study revealed that ecological activity in the graminoid wetlands is significantly higher on a per- unit- area basis than that of the cypress and mangrove wetlands or of Florida Bay. This is especially true of its role in the sequestering of carbon. A full set of eight networks of four South Florida wetland habitats has been provided to serve as benchmarks in calibrating the ATLSS simulations. In addition, the website containing the data and the annual reports serve as a rich data resource for all ongoing South Florida ecological investigations.

Application to Everglades Restoration: Networks constitute a necessary preliminary to running the ATLSS model. Compiled data represents an extremely valuable library resource for all biological modeling activities in South Florida. (Available on the Web at http://www.cbl.umces.edu/~atlss.). A valuable potential addition to USGS' South Florida Ecosystem Database http://www.envirobase.usgs.gov.