Project Summary Sheet

Study Title: Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay
Study Start Date: 3/15/02 Study End Date: 9/30/06
Web Sites: http://sofia.usgs.gov/flaecohist/; http://sofia.usgs.gov/exchange/index.html
Location (Subregions, Counties, Park or Refuge): Biscayne National Park, Miami-Dade County, Monroe County
Funding Source: USGS Greater Everglades Priority Ecosystems Science (GE PES Initiative); South Florida Water Management District (Previous FY - not in 2005)
Principal Investigator(s): G. Lynn Wingard
Study Personnel: (For FY05) Thomas Cronin; Chuck Holmes; William Orem; Debra Willard; L. Wingard; C. Bernhardt, C. Budet, T. Lerch, M. Marot; J. Murray; R. Ortiz, US Geological Survey.
Supporting Organizations: South Florida Water Management District; Biscayne National Park
Associated / Linked Studies: Paleosalinity as a Key for Success Criteria in South Florida Restoration; Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area; Monitoring Sub-Aquatic Vegetation through Remote Sensing: A pilot study in Florida Bay; and Synthesis of South Florida Ecosystem History Research. Also, DOI Landscape Initiative with Biscayne National Park (USGS Lead: Sonya Jones)

Overview & Objective(s): The objectives of this project are to examine in broad context the historical changes in the Biscayne Bay ecosystem at selected sites on a decadal-centennial scale, and to correlate these changes with natural events and anthropogenic alterations in the South Florida region. Specific emphasis will be placed on historical changes to 1) amount, timing, and sources of freshwater influx and the resulting effects on salinity and water quality; 2) shoreline and sub-aquatic vegetation; and 3) the relationship between sea-level change, onshore vegetation, and salinity. In addition, a detailed examination of historical seasonal salinity patterns will be derived from biochemical analyses of ostracodes, foraminifers, molluscs, and corals. Land management agencies (principally SFWMD, ACOE and Biscayne NP) are using the data derived from this project to establish performance criteria for restoring natural flow, and to understand the consequences of altered flow. These data can also be used to forecast potential problems as upstream changes in water delivery are made during restoration.

Status: SFWMD contract was completed in FY04, so in FY05 we have focused our efforts on conducting additional analyses on samples to refine age models and preliminary interpretations of cores by filling in data gaps. Part of refining the age model includes developing a carbon correction factor for Biscayne. This work is underway with C-14 analyses of modern samples completed, and the analysis of modern water samples begun. Current C-14 models use data from the Dry Tortugas, but the enclosed nature of Biscayne Bay necessitates a local correction factor based on the dynamics of the Bay. We also are working with our clients and partners to determine if additional new cores need to be taken to fill information needs for the DOI Landscape Initiative and the RECOVER Southern Estuaries Team.

Recent Products:
OFR 2004-1312 was published in December 2004 and is Part II of OFR 03-375, published in 2003. A factsheet also was released in the Fall 2004 (FS 2004-3108). Abstracts summarizing the results of our Biscayne work were published in NERC, George Wright Society (NPS), and AGU meeting volumes. Oral presentations have been given to Biscayne National Park (October 2004) and to the Southern Estuaries Sub-Team of the RECOVER Regional Evaluation Team (June 2005).

Planned Products:
A short article will be published in the NPS George Wright Society Special Issue: Forum on Geodiversity. A series of journal articles summarizing different aspects of the ecosystem history study of Biscayne Bay are planned by the individual scientists. T. Cronin has been submitted an article to the journal "Climate Change" on the role of climate change in restoration of estuaries.

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/]:

One of the primary DOI activities discussed in the DOI Science Plan is to "ensure that hydrologic performance targets accurately reflect the natural predrainage hydrology and ecology" (DOI Science Plan, p. 14). The primary goal of the Ecosystem History of Biscayne Bay study is to determine the predrainage hydrology and ecology of the Bay and surrounding wetlands. Data from this project has been requested by and is being used by the Southern Estuaries Sub-Team (SET) of the Regional Evaluation Team (RET) of RECOVER to set performance measures (PMs) for Biscayne Bay. This team includes clients from DOI-NPS, DOI-F&WS, NOAA, ACOE, and SFWMD. Recent data obtained by SET through the simulations run for the Initial CERP Update (ICU) have returned salinity values far in excess of any anticipated; they have therefore turned to our paleosalinity data as the primary tool for setting the PMs for Biscayne Bay.

Additionally, this study supports the Biscayne Bay Coastal Wetlands Project and the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study, and it provides information relevant to the Combined Structural and Operational Plan (CSOP), Landscape Modeling, Invasive Exotic Plant Detection, and Monitoring and Aquatic Exotic Animals Projects. This study supports these projects by 1) conducting research to understand the predrainage hydrology, including the amount, timing and seasonality of freshwater delivered to the bay historically; 2) examining the historical environmental conditions, including the linkage between hydrology (water quality and quantity), ecology, and habitats; 3) providing the modelers with data on historic conditions in order to set targets and performance measures that reflect natural hydrologic patterns; 4) providing long-term historical data on trends and cycles within the biological component of the ecosystem that can be forecasted to predict the effects of implementation of hydrologic restoration on the ecology of coastal communities; and 5) by determining the timing of introduction and spread of exotics in the Biscayne Bay ecosystem and the coincident changes in the native species.

This study supports the Biscayne Bay Coastal Wetlands Project by addressing the questions "How much freshwater, and in what seasonal patterns, was delivered historically to Biscayne Bay?" (DOI Plan, p. 63), "What are the links between hydrology and ecology in the Biscayne Bay coastal wetlands?" (p. 64), and "What are the key indicators of natural ecological response . . ." and "what are the baseline conditions of the indicators?" (p. 66). The data generated by this project are particularly valuable because they provide 100 to 500 years worth of data on changes to the system.

This study supports the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study by addressing the questions "What were the physical and ecological conditions in . . . Biscayne Bay prior to drainage and modification . . ." (DOI Plan p. 63), "What are the hydrologic targets needed to mimic historic flows . . . ? (p. 63).

In addition, the study contributes to the Combined Structural and Operational Plan (CSOP) and Landscape Modeling projects by providing historical ecological data on trends and cycles that can be forecasted to predict the effects of implementation of hydrologic restoration on the ecology of coastal communities. This addresses questions of the impact of increased flow (p. 63), and expected faunal and floral responses (p. 64, p. 79, p. 80). The study also contributes to the Invasive Exotic Plant Detection and Monitoring and Aquatic Exotic Animals Projects by determining the temporal and spatial distribution of exotics and changes in native species coincident with introduction (p. 118).

Key Findings:

1. The salinity of Biscayne Bay has been steadily increasing over time in all nine cores examined to date. Although the timing and onset of increased salinity varies at the different core sites, there are no exceptions to this trend.
2. Sites in both central and southern Biscayne Bay show indications of increasing marine influence at the sites. These trends could be a result of rising sea level, of changes to the natural flow of fresh water or both, but the timing of changes at some of the near-shore sites suggests both factors are involved.
3. In near shore areas, distinct, but site specific, changes in freshwater influx over time have occurred, and our data suggest that some sites we assumed had historic point-source inflow of fresh water did not, even prior to human alteration of the natural environment. Wetlands sites in very close proximity to each other have historically been affected by very localized hydrologic regimes.
4. Implications for managers: 1) Biscayne Bay appears to be evolving toward a more marine environment and sea-level rise should be factored into the planning process; 2) generalized performance measures and targets for the near-shore and wetlands areas may not reflect the natural variability seen at these sites; and 3) mid-Bay sites are very different from near-shore sites and have been for hundreds of years, therefore restoration targets should not seek uniformity in benthic environments.