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projects > sedimentation, sea-level rise, and circulation in florida bay > 1998 Proposal

Sedimentation, Sea-Level Rise and Circulation in Florida Bay

Project Proposal for 1998

Program:Fragile Environments Program
Project Title: Sedimentation, Sea-Level Rise, and Circulation in Florida Bay
Location of Study Area: Florida Bay, Florida
Project Start Date: FY1995
Project End Date: FY1999
Project Number: 7242-37655
Project Chief: Robert B. Halley
Region/Division/Team/Section: Eastern Region/Geologic Division/M&CG Team/ St. Pete
Phone: (813) 893-3100
Fax: (813) 893-3333
Mailing Address: USGS Coastal Center, 600 4th St. South, St. Petersburg, FL 33701
Program Element(s)/Task(s) South Florida Study Area, Element 6 (Florida Bay, Florida Keys, and the Coral Reefs), Task 6.3 (Mud Banks)
Panel: NA
Collaborators, Clients:
Tom Armentano, Robert Brock (Everglades National Park, Florida Bay Program Coordinators)
Ron Hilton, Mike Choate (ACOE, Jacksonville FL, South FL Restudy)
Susan Olson (South Florida Water Management District, Florida Bay Program Supervisor)
Bill Krisincky (EPA, Florida Keys Water Quality Program Manager)
John Hunt (FL Department of Environmental Regulation, Florida Keys Program Manager)
Billy Causey (NOAA, Florida Keys National Marine Sanctuary Coordinator)
David Rudnick (South Florida Water Management District)
Bill Lyons (Florida Department of Environmental Protection)


Project Summary: The goal of this USGS project is to document decade- to century- scale processes associated with sediment transport in Florida Bay. The results will quantify the influence of bottom topography on water quality in the Bay so that sea level and bathymetric change can be integrated with numerical modeling efforts conducted by cooperating agencies.

Project Justification: Recent algal blooms and seagrass mortality have raised concerns about the water quality of Florida Bay, particularly its nutrient content (nitrogen and phosphorous), hypersalinity, and turbidity. Water quality is closely tied to sediment accumulation because mudbanks severely limit circulation in the bay. Over decades to centuries, bathymetric changes due to erosion or sedimentation affect water circulation and hypersalinity. The impact on circulation depends on the interplay between sediment accumulation and sea-level rise. Management agencies are planning a "restoration" of Florida Bay that centers around increasing the amount of fresh water entering the estuary. In order to predict the results of various restoration alternatives, long-term changes in the bathymetry and volumetrics of the bay must be Incorporated in hydrodynamic models being constructed by other agencies.

Project Objectives:Five interrelated activities are underway for this project: 1) core analyses; 2) local sediment elevation surveys; 3) mudbank profiling and surveys; 4) integration of sedimentary analyses with circulation patterns and sea-level history; and 5) salinity surveys to document effects of mudbanks on circulation;. This project integrates results from several other ongoing and new projects in the USGS Ecosystem program and other programs. In particular, the bathymetry, turbidity, sediment transport, lead-2 10 dating, and ecosystem history projects in the bay both use results from this project and provide information to the project. Additional complimentary information is being provided by the Marine and Coastal Program project "Sedimentation and water quality in Florida Bay" that provides funding for determining past salinity from geochemical analyses of fossil mollusks as part of a cooperative with the South Florida Water Management District. It is a goal of the work proposed here to integrate these various projects into a sediment budget for Florida Bay

Overall Strategy, Study Design, and Planned Major Products: Four of five activities are designed to provide measures of sedimentation or erosion on mudbanks, the fifth activity documents the influence of mudbanks on water salinity.
1) Coring: Cores taken for this and other projects have been x-rayed and some provide measurable sections of sediment above known (dated) horizons. These provide an average sedimentation rate based on the age of the horizon.
2) Pb-210 dating: A few cores are suitable for lead-210 dating from which an average sedimentation rate can be calculated. The lead-210 method has the advantage of providing a continuous record of sedimentation rates during the last century with a resolution of a few years. However, there are only a few sites in the Bay that are suitable for analyses.
3) Sedimentation site monitoring: Fifteen local sediment survey stations have been established in the bay. These are driven to bedrock and provide platforms for seasonal sediment elevation measurements accurate to a few millimeters. Five are in the eastern bay, five in the central bay, and five in the western bay.
4) Bank profiles: Each group of five survey stations is arranged in a transact across a mudbank. Repeated precision profiling across each mudbank will provide a multi- year record of sediment erosion or accretion on the bank and allow the data from individual survey stations, cores, and marker horizon sites to be placed in context of bank-wide patterns. Sedimentation rates provide basic data for determining long-term accumulation/erosion patterns and subsequent volume changes in the bay as a result of sea- level rise.
5) Salinity surveys: Salinity maps, produced semi monthly, illustrate the influence of mudbanks on circulation. The contours of salinity, constructed from bay-wide surveys, show conformity with the banks and often coincide with the banks. Turbid and algal bloom regions, monitored by other agencies, are also confined by shallow banks. Three measures of water quality (salinity, turbidity and chlorophyll) indicate that the mudbanks are a dominant control on circulation. Understanding mudbank dynamics is critical to predicting future water quality of the Bay.


Overall:During FY 1998 data will be collected from all the stations and dating work will continue on sediment cores. The establishment of elevations of NPS tide gauges (during late FY1997 and early FY1998) allows the placement of bank transects on a geoid reference frame relative to sea level. During FY 1998 sea-level and elevation data will be processed so that, for the first time, exposure indices of mudbanks can be calculated, providing quantitative measures of bank flooding and drying. Sediment production rates will be refined by measuring the carbon-14 activity of core intervals already dated by the lead-2 10 method in order to determine how much sediment has been produced during the past 35 years (using carbon-14 produced during atmospheric nuclear testing as a tracer). During FY 1998 initial synthesis of production , sedimentation and erosion rates, will begin in anticipation of completion in FY 1999. During FY1999, results from a sediment transport model, will allow development of a sediment budget for the bay.

Timeline: Regular (semimonthly) meetings are planned with clients through committee and group activities and as required by our cooperative agreement. Field work is planned for four weeks each summer, in two two-week sessions (July and August), and two weeks at the end of the wet season and two weeks at the end of the dry season. Field work is subject to delay or extension pending weather, furloughs, availability of boats and vehicles, etc. Product completion is described in next section. This project also supports USGS and interagency administrative activities associated with the Task Force for South Florida Ecosystem Restoration, in particular the steering committee, theme coordinator activities in the USGS, as well as interagency Science Subgroup and Florida Bay Program Management Committee activities.

Planned Deliverables/Products: Analyses cores from three mudbanks will be summarized in a manuscript for a special volume of Estuaries dedicated to long-term change in Florida Bay. A final report will detail initial results and results from duplicate cores at project end. Each year presentations are prepared for the USGS South Florida Program Meeting, the Florida Bay Science Conference, and a national scientific society meeting, either GSA, AGU or SEPM. Presentations are prepared for client workshops (SFWMS, ACOE, NOAA, and NPS). Often these meetings are unknown in time for workplans, For example, on May 10th the ACOE has invited the USGS to a workshop "Modeling Sediment Resuspension, Water Quality And Aquatic Vegetation" in New Orleans, June 24-25, 1997. This is the third unscheduled client workshop this FY. A presentation will be prepares for the annual USGS program meeting. Abstracts will be written, reviewed and approved for all meetings that require formal presentations. One journal manuscript will be prepared. Semimonthly salinity maps of Florida Bay will continue to be produced. All results are posted on the internet or presented at science meetings. Results are conveyed to management at managers meetings, through workplans, proposals, and reports.

Planned Outreach Activities: During FY 1998 client requirements will continue to be met through continued regular client meetings, through direction from the Florida Bay Interagency Science Program Management Council, and through continued interaction with collaborators and clients listed above in the first section.

Prior Accomplishments in Proposed Area of Work:

New Directions, Expansion of Continuing Project (if applicable): This project does not anticipate new directions or expansions. It does however support the principle investigator's time and travel on long range planning for the Florida Bay PMC (see product #9) and the USGS South Florida Program.


Accomplishments and Outcomes, Including Outreach: Successful completion of Phase One of our contract work on Ecosystem History with the South Florida water management district has led to a renewal of this work during FY1997. My time constraints have prevented me from taking on the renewal, and the project is now in the capable hands of Chuck Homes. Continued to serve as GD representative to Program and Florida Bay Coordinator and represent the USGS on the Interagency Florida Bay Program Management Council.

Deliverables, Products Completed:
1. Open File Report 96-634, Florida Bay Surface Salinities Nov. 1994, Jan., Apr., June, Aug., Oct., Dec., 1995, Feb., Apr., June 1996. Maps for Aug., Oct., Dec., 1996 and Feb., Apr., June 1997 available by end of FY 1997.
2. Contributions to South Florida Ecosystem Website (2)
3. "Seagrass Facies and Phases Recorded in the Sediments of Florida Bay", abstract and presentation at the First Annual Wait Dineen Society Meeting, May 22-24, 1997, Miami Beach, FL.
4. "Seagrass Mortality and Substrate Response", abstract and presentation at the Southeast Estuarine Research Society, April 10- 12, 1997, Islamorada, FL.
5. "Florida Bay Mudbanks: Relatively New Piles Of Mostly Old Sediment", abstract and presentation at the USGS S. FL. Ecosystem Symposium, August 25-27, 1997, Fort Lauderdale, FL.
6. "Sediment Transport Processes and Sea-floor Mapping" (with Ellen Prager), abstract, Florida Bay Science Conference, Dec 10-12, 1996, Key Largo FL.
7. "Analyzing the Isotopic Record of Coral and Mollusk Skeletons to Relate Past Salinity and Nutrient Levels in Florida Bay" (with Peter Swart), abstract, Florida Bay Science Conference, Dec 10- 12, 1996, Key Largo FL.
8. Halley, R. B., Vacher, L. H., Shinn, E. A. 1997 Geology and hydrogeolgy of the Florida Keys, in Vacher, H. L. and Quinn, T. E., editors, The Geology and Hydrogeology of Carbonate Islands, Elsevier, New York, pp. 217-248.
9. "Strategic Plan for the Interagency Florida Bay Science Program", 1977, member of writing team.


Required Expertise: Local knowledge of Florida Bay, carbonate sedimentology, marine geological field methods, laboratory methods, public speaking, scientific writing, report writing, popular writing, drafting, statistics, contracting, budgeting, planning, sales techniques, quality control, outreach. It has been particularly difficult to retain personnel. At the present moment, however, these problems are solved for the short-term. The difficulties could return at any moment. The main personnel issue is holding qualified people in temporary positions. Primary expertise issue is setting of priorities for core capabilities and operations in St. Pete office.

Names of Key Project Staff: (R. B. Halley, E. M. Prager, Chuck Holmes, L. Roulier, R. Byrd, Richard Sanders, two unidentified interns: one for lab work, one for salinity surveys)

Major Equipment/Facility Needs:Sedimentological laboratories, core processing facility, boat, marine coring barge and equipment, data processing, drafting and illustrating, and manuscript preparation facilities.

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