geochronology in the south florida
ecosystem and associated ecosystem programs >
Project Proposal for 1998
Program: FRAGILE ENVIRONMENTS
Project Summary: Many ecological questions require temporal information before a management decision can be reached. This projects supplies the important time series information for process-based studies (both in the terrestrial and coastal environment), time information for the ecological and fire history research, the timing of sealevel rises and storm events, the rate of sediment transport and deposition in Florida Bay and the "age" of ground water seeping under the fringing topographic ridge.
Project Justification: Resource managers, in order to provide adequate leadership in balancing the environment between natural and anthropogenic needs, must understand how the natural system works. The document South Florida Ecosystem Restoration: Scientific Needs list many such questions requiring temporal data in the answer. The timing of chemical loading in the terrestrial or coastal zones, or the formation of certain features which affect water flow is of paramount importance to management of the natural resources within the South Florida Area. This project will provides information on the timing of events.
Project Objectives: Over the past three decades there has been a dramatic increase in the volume and range of research on recent sediments. Much of this research effort has been aimed at understand short-lived sedimentologic processes and the result of anthropogenic manipulation of natural processes. In south Florida, ecological changes have alarmed all who are concerned with maintaining the south Florida way of life. In order to understand what has influenced the natural processes that have caused these changes, it is necessary to understand the processes at work within the system and to determine the rates at which these changes are occurring. The lack of historical records documenting changes dictates that other methods be used to measure "rates of change." A common method is to use the decay of naturally occurring radioactive nuclides. The usefulness of any radioactive nuclides requires certain conditions be met. These conditions are 1. the chemistry of the nuclide (element) is known; 2. The nuclide onces incorporated into the substrate changes only by decay, and 3. in order to be useful, it is relatively easy to measure. The objectives of the project is to measure the distribution of short- lived radionuclides to provide a temporal component to the processes at work within the Ecosystem.Overall: Sufficient data has been collected in the South Florida Region and in Chesapeake Bay to confirm that the radiometric methods proposed do yield a valid chronology. The ecological variability within the South Florida Area, however, is considerable requiring that a separate chronology be ascertained for each site of interest. Because of different analytical methods require a lot of sediment, many "dated" cores will be adjacent to those used for geochemistry. For the ecological and fire history studies, the same core will be used. The emphasis this year is to understand the processes that have worked and are working within the Taylor Slough area, define a chronology of ecological change in Chesapeake Bay, and define the changes in the chemical systems in Florida Bay.
A poll of the investigators presently working in the south Florida Ecosystem and the
Chesapeake Bay program has indicated the following needs for the coming year:
These projects have indicated a need to have a chronological record established for 36 sites. It is proposed that a chronology at various sites will be established by used of natural and man-made short-lived radioisotopes (7Be, 137CS, 21OPb, in some case's uranium/thorium, or 14C).
FY 1998 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Analysis of: Taylor. Cores ------------------------------------------------- Fla.Bay and Adjacent Bays Cores -------------------------------------------------- Chesapeake Bay ----------------- Florida Bay meeting ---- Measurements of sediment/fluid transport ------------------------------------------------- Year Report -------
Planned Deliverables/Products: As this is primarily a support project that is providing data to other projects, most to the data is incoportated in the products of others. This data is supplied in a timely fashion to those projects chiefs and has been and is being used in their reports. In additon speicific chronology reports are being prepared which deal with the analysis of the chronological data and the probelms of using some elements without confirmation.
Planned Outreach Activities: The information derived from this project will be presented at the anual meeting of the Ecosystem program, the Ecological history workshop, and at the international Environmental Geochemical meeting. In addtion, the Paelocological investigators will be present data from this project at the AGU on other conferences dealing with the presentaion of this data.
New Directions, Expansion of Continuing Project (if applicable):
The addition of low-level counting
equipment has added a new dimension to the cabablitiy of the geochronology project. In
addition to measuring timing of events on decadal time scales, we are now capable of measuring
events on a daily time scale. This allows us to determine such processes such as how much
sediment is eroded during a single event such as storm, or flood. Such information will allow us
to determine the transportation of sediment within system, information that is important in the
developernent of water qualitiy models, such as t he one presently being developed for Florida
Bay. This part of the project addresses the issues that are part of Element 6 / Task 6.3. These
systems also permit the measurement the flow of ground water by the determination of the
relative amount of "tracer" isotopes in fluid "leaking" from the strata. There are numerous
pieces of evidence that "tracer" loaded fluid are interacting with the bay water and sediment.
This new direction would be an attempt to quanitify this interaction.
Deliverables, Products Completed:
Names of Key Project Staff:
Major Equipment/Facility Needs: Laboratory and counting equipmental