Project Summary Sheet

Project: Application of Stable Isotope Techniques to Identifying Foodweb Structure, Contaminant Sources, and Biogeochemical Reactions in the Everglades

Web Sites: http://sofia.usgs.gov/; http://Everglades.fiu.edu/BRD (see http://everglades.fiu.edu/index.htm); http://www.fcsc.USGS.gov (see http://cars.er.usgs.gov/); http://flaecohist.er.usgs.gov;

Location (Subregions & Counties): Total System: Palm Beach, Broward, Dade, Monroe, Okeechobee, Martin, Highlands, Glades, Hendry, and Collier Counties

Funding (Source): USGS Place-Based Studies

Principal Investigator(s): Carol Kendall, ckendall@usgs.gov, 650.329.4576.

Project Personnel: Scott D. Wankel, sdwankel@usgs.gov, 650.329.4303; Bryan E. Bemis, bebemis@usgs.gov, 650.329.5603; Steven R. Silva, srsilva@usgs.gov, 650.329.4558.

Supporting Organizations: South FL Water Management District, FL Game and Fresh-water Fish Commission, US EPA

Associated / Linked Projects: Integrated Biogeochemical Studies in the Everglades, South Florida (Orem, borem@usgs.gov, 703.648.6273; Krabbenhoft, dpkrabbe@usgs.gov, 608.821.8181)

Overview & Status: The scientific focus of this project is to examine ecosystem responses (especially variations in foodweb base and trophic structure) to variations in hydroperiod and contaminant loading, and how ecosystem restoration steps may affect spatial/temporal changes in foodwebs and MeHg bioaccumulation. Major recent changes in focus include enhanced collaborations with SFWMD personnel to (1) investigate isotopic compositions and trophic structures in ENR and STA’s, (2) extend our foodweb studies beyond fish to bird and alligator populations, and (3) link our data on seasonal differences in foodweb bases and trophic levels with SFWMD Hg datasets. A new collaboration (intended to be part of Scott Wankel’s dissertation at Stanford) will investigate the effects of seasonal/spatial changes in nutrients, water levels, and reactions on the isotopic compositions at the base of the foodweb. We have also increased our collaborations with FGFWFC, have almost finished the analysis of the many samples collected for us by REMAP 99, and have successfully linked our USGS foodweb isotope data with the spatial patterns observed in the REMAP 96 isotope dataset (a major synthesis and achievement).

Needs & Products: Our main need is sufficient funds to support (1) Bemis to help me finish the interpretation and publication of our existing foodweb isotope data; and (2) Wankel’s Everglades dissertation (at Stanford). He tentatively plans to (a) investigate how temporal/spatial changes in nutrients, processes, and hydroperiod affect the establishment of algal vs detrital-based foodwebs, and (b) provide a better linkage of our spatial/temporal isotope data and the spatial data and foodweb models developed by the REMAP program. Recent products include many talks/posters, a few minor publications, 2 major synthesis papers in review, currently 3 more in various stages of preparation, and a database ready for the web.

Application to Everglades Restoration: (1) Biota isotopes provide a map of the current spatial distributions of the extent of several biogeochemical reactions (esp. sulfate reduction) affecting nutrient and Hg uptake. (2) By comparing the spatial patterns in the biota with those in the shallow sediments, recent anthropogenic changes in biogeochemical processes at the landscape scale can be demonstrated and dated. (3) Isotopes provide detailed information about temporal and spatial changes in trophic relations that complements traditional gut-contents analyses used by the FGFWFC (and others) for understanding foodwebs and the bioaccumulation of contaminants. (4) The preliminary synthesis of the biota isotopes at USGS and 1996 REMAP sites provides a mechanism for extrapolating the detailed foodwebs developed at the intensive USGS sites to the entire marsh system sampled by REMAP. (5) Biota isotopes provide a simple means for monitoring how future ecosystem changes affect the role of periphyton (vs. macrophyte-dominated detritus) in the gambusia foodchain, and for predictive models for MeHg bioaccumulation under different proposed land-management changes.(6) Since the REMAP spatial data are likely to be an important "benchmark" for assessing ecosystem changes, it is critical that these data be critically evaluated in the context of data generated by the USGS and local FL agencies; we are among the few scientists who are trying to "justify" the different perspectives and data generated by the USGS and EPA teams.