Project Summary Sheet

Project Title: Monitoring Sub-Aquatic Vegetation through Remote Sensing: A Pilot Study in Florida Bay

Project Start Date: 10/1/02 Project End Date: 9/30/05

Web Sites: http://sofia.usgs.gov/flaecohist/

Location (Subregions, Counties, Park or Refuge): Florida Bay, Everglades National Park, Monroe County

Funding Source: USGS's Greater Everglades Science Initiative (PBS); funding requested from Land Remote Sensing Program for FY03 but did not receive, so only Task 3 of project funded.

Principal Investigator(s): G. Lynn Wingard

Project Personnel: For Task 3: Chuck Holmes, Marci Marot, James Murray.

Supporting Organizations: South Florida Water Management District; Everglades National Park

Associated / Linked Projects: 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 are 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. The ultimate goal is to develop a method for forecasting potential sea-grass die-offs and to determine if remediation efforts would be cost-effective. Florida Bay is selected for the pilot study because the thorough documentation of the 1987-1988 die-off event provides 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. A 10-15 km² portion of Florida Bay that encompasses areas affected by the 1987 and 1999 die-offs will be analyzed for this pilot study. Geologic, biologic and remotely sensed data will be integrated and analyzed 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 has begun. Tasks 1 and 2: No real progress has been achieved because these tasks are unfunded. Background research and inquiries on different remote sensing platforms has been completed and a dialogue initiated with John Brock (USGS, St. Petersburg) on use of EAARL data for this project and possible links to his coral work in Biscayne NP. Preliminary surveys of areas targeted for high-resolution field mapping have been conducted.

Recent & Planned Products: Abstract and poster for GEER/Florida Bay Science Conference. Report on Rankin core will be completed by Fall 2003.

Relevance to Greater Everglades Restoration Information Needs: 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. A major question persists - are changes in freshwater flow a factor in seagrass die-offs. This research attempts to address that question and as a result will provide information relevant to all three restoration goals listed by the task force - to get the water right, to restore preserve and protect natural habitats and species, and to foster compatibility between the built and natural systems. This project also addresses several USGS restoration science objectives: SO1, understanding ecosystem structure and function; SO2, determining the historical ecosystem setting; SO3, establishing baselines and targets; and SO5, predicting ecosystem response to change. By examining the causes of die-off and the natural patterns of change in seagrass meadows over biologically significant periods of time we can determine the components of change that may be related to anthropogenic activities versus natural cycles of change. This information would allow resource managers to make informed decisions about the cost-effectiveness of and mechanisms for remediation.

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

• 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.
• 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.
• 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?