Project Summary Sheet

Study Title: Monitoring Sub-Aquatic Vegetation through Remote Sensing: A pilot study in Florida Bay
Study Start Date: 10/1/02 Study End Date: 9/30/04
Web Sites: http://sofia.usgs.gov/flaecohist/
Location (Subregions, Counties, Park or Refuge): Florida Bay, Everglades National Park, Monroe County
Funding Source: USGS Greater Everglades Priority Ecosystems Science (PES) Initiative
Principal Investigator(s): G. Lynn Wingard
Study Personnel: For Task 3: Chuck Holmes, Marci Marot, James Murray.
Supporting Organizations: South Florida Water Management District; Everglades National Park
Associated / Linked Studies: Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay; Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area; Paleosalinity as a Key for Success Criteria in South Florida Restoration

Overview & Objective(s): Seagrass beds are essential components of any marine ecosystem because they provide feeding grounds, nurseries, and habitats for many forms of marine life, including commercially valuable species; they are important foraging grounds for migratory birds; and they anchor sediments and impede resuspension and coastal erosion during storms. This valuable natural resource has been suffering die-offs around the world in recent years, yet the causes of these die-offs are undetermined. The objectives of this pilot study were to develop a methodology for monitoring spatial and temporal changes in sub-aquatic vegetation using remote sensing, satellite imagery, and aerial photography, and to analyze potential causes of seagrass die-off using geographic, geologic and biologic tools. Florida Bay was selected for the pilot study because the thorough documentation of the 1987-1988 die-off event provided a baseline for examining data preceding and succeeding the event. In addition, a small well-studied die-off occurred in 1999-2000 at Barnes Key in Florida Bay. The plan for the remote sensing component (never funded) was to select a 10-15 km² portion of Florida Bay that encompassed areas affected by the 1987 and 1999 die-offs to analyze. The objective was to integrate geologic, biologic and remotely sensed data to determine the patterns of change and sequences of events that occur in healthy seagrass beds and in beds undergoing a die-off.

Status: Task 3: Analyses of core from Rankin Basin die-off area were completed in FY03. Processing of Barnes core was completed and picking of molluscan fauna began, but study personnel were diverted to higher priority PES studies. Tasks 1 and 2: No real progress has been achieved because these tasks were not funded.

Recent Products: Abstract and poster for GEER/Florida Bay Science Conference 2003.

Planned Products: Fact sheet on modern experiments (early FY04), potential OFR and/or journal article if time and priorities allow.

Specific Relevance to Information Needs Identified in DOI's Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida (DOI's Everglades Science Plan) [See Plan on SOFIA's Web site: http://sofia.usgs.gov/publications/reports/doi-science-plan/]:

Seagrass die-off is not a specific unanswered question in the DOI Science Plan; however, it is an issue of concern to the Florida Bay and Florida Keys Feasibility Study (DOI Science Plan, p. 76), the Southwest Florida Feasibility Study (p. 52), and the Biscayne Bay Coastal Wetlands Study (p. 72). Seagrass is a critical habitat to the estuarine systems, thus understanding the ecology of seagrasses is essential to restoration of the habitat. The large scale die-off of seagrass in Florida Bay in 1987-88 was one of the primary factors stimulating a move towards restoration of more natural freshwater flows into Florida Bay. This study contributes to the Landscape Modeling project by providing historical ecological data on trends and cycles within the seagrass habitats that can be forecasted to predict the effects of implementation of hydrologic restoration on seagrass communities and the fauna they support. This addresses questions of the impact of increased flow (p. 63), and expected faunal and floral responses (p. 64, p. 79, p. 80).

Key Findings: Several significant findings have emerged from the preliminary analyses of the Rankin Basin core:

1. Prior to the seagrass die-off, the mollusks and ostracodes indicate an increase in the amplitude of salinity fluctuations; these data illustrate that increased salinity variation may have been a factor in the die-off.
2. Molluscan epiphytes and Loxoconcha appear to have gone through several cycles of build-up and decline at the Rankin site, indicating perhaps die-offs occurred at the site in the past. However, the degree of build-up and decline in the Thalassia indicators is unprecedented below 50 cm illustrating that this was an exceptional event.
3. Something significant happened in the environment at Rankin Basin at around 50 cm in the core, because virtually all parameters measured show significant changes between 50 and 30 cm. Once an age model for the core is worked up, we can examine possible cause and effect questions. Did the die-off event trigger the changes seen in the core, or did other environmental variables change significantly, thus triggering the die-off?