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Thomas Cronin, Debra Willard, Charles Holmes, William Orem, Gary Dwyer (Duke University)
First, the environmental preferences and distributions of modern fauna and flora are established through analyses of modern samples in south Florida estuaries and coastal systems. Much of these data have already been obtained through project work conducted in Florida Bay and the terrestrial Everglades starting in 1995. These modern data are used as proxies for interpreting the historical data from Pb-210 and C-14 dated sediment cores based on assemblage analysis. On the basis of USGS data obtained from cores in Florida Bay and Biscayne Bay, the temporal span of the cores should be at a minimum the last 150 years; this is in agreement with University of Miami data showing sedimentation rates in Whitewater Bay to be approximately 1cm/year. For the estuarine/coastal ecosystems, a multidisciplinary, multiproxy approach will be utilized on cores from a transect from Whitewater Bay north to 10,000 Islands. Biochemical analyses of shells and chemical analyses of sediments will be used to refine data on salinity and nutrient supply, and isotopic analyses of shells will determine sources of water influx into the system. Nutrient analyses will be conducted to determine historical patterns of nutrient influx. To examine the inland migration of the mangrove/coastal marsh ecotone, transects from the mouth of the Shark and Harney Rivers inland into Shark River slough will be taken. These cores will be evaluated for floral remains, nutrients, charcoal, and if present, faunal remains.
This project will provide 1) baseline data for restoration managers and hydrologic modelers on the amount and sources of freshwater influx into the southwest coastal zone and the quality of the water, 2) the relative position of the coastal marsh-mangrove ecotone at different periods in the past, and 3) data to test probabilities of system response to restoration changes.
Cronin, Thomas M.; Holmes, Charles W.; Willard, Debra A.; Budet, Carlos A.; Ortiz, Ruth E.
Weimer, Lisa M.; Riegel, W. L.
Holmes, C. W.; Weimer, L. M.
Budet, Carlos A.; Ortiz, Ruth E.; Hudley, Joel; Murray, James B.
Processing of all core samples from the southwest coastal area has been completed. Core samples were processed using standard methods and all fractions were retained for analyses. A portion of the less than 63-micron fraction has been used for Pb-210 geochronology. The greater than 63-micron fraction has been sorted for faunal analyses; ostracodes, molluscs and benthic forams have been picked and sorted and identification of the Shark River Transect cores completed. Identification and analyses of the Harney and Lostmans transect cores will be completed in FY08. Percent abundance is calculated for the faunal data, and these data are compared to the modern proxy data. The down-core faunal assemblages and the presence or absence of key indicator species allows interpretation of trends in salinity, water quality and the presence of SAV at the site.
Analysis of faunal and floral remains, geochemistry and geochronology of three cores forming a transect up Shark River Slough have been completed and are currently being compiled for a report planned for release in Fall 2007. Age models for the cores have been completed and a database of modern analogue data for nearshore environments has been significantly augmented in FY07, improving our interpretation of the downcore data. Processing of all cores from the southwest coastal area was completed in FY07. Sorting and identification of samples from the Harney River Transect is underway.
Analyses of Shark River transect cores was completed in FY07, and Harney River and Lostmans River transects will be completed in FY08. Pollen work will be coordinated with faunal assemblage analyses under the geochronology and paleoecology task. Additional marsh core transects may be planned for collection in FY08, or material from previous collections in the area may be utilized.
We will reconstruct the position of the coastal marsh-mangrove ecotone at selected time slices during the last few centuries, with the greatest detail provided for the last century. Reconstructions will be based on analysis of pollen, seeds, charcoal, and microfaunal assemblages from sediment cores collected in a transect along Shark River from fresh water marshes to mangroves at the river mouth. (Location of transects will be coordinated with task 1.) These sites correspond to existing vegetation and SET (Surface Elevation Table) sites SH1-5 and some water monitoring sites that are part of the Tides and Inflows in the Mangrove Ecotone (TIME) study. Cores also will be collected at Big Sable Creek. Cores will be described sedimentologically before paleoecological analyses.
Based on previous radiometric dating of peat cores from the Everglades (Willard et al, 2001a; 2001b), sampling intervals of 1 - 2 cm should provide adequate temporal resolution to identify vegetational and environmental changes on sub-decadal scales for the 20th century. Geochronology will be established using a combination of cesium-137 and lead-210, which provides good age control over the last 100 years, and radiocarbon dating, which provides age control over centennial to millennial time scales.
The natural variability of the system will be established through analysis of pre-drainage sediments. Globally documented climatic events may have elevated temperature as much as climate models predict for the 21st century, and an understanding of the past response of the system to such perturbations will provide important information to policymakers in designing restoration plans that incorporate expected climate variability.
Data on the timing and extent of salinity changes at the freshwater wetland-mangrove marsh ecotone will be used for calibration and verification of the TIME Study hydrodynamic and transport model being developed for the entirety of Everglades National Park.
Extensive work in the nearshore area of Biscayne Bay has provided relevant additional proxy information on species present in the southwest area. We plan to conduct modern field work in FY08 in the southwest area to fill in a few remaining gaps in the modern analogue dataset. In addition, we plan to collaborate with Florida Gulf Coast University (Dr. Michael Savarese) and share data and resources for modern calibration work.
In FY08, we will conduct analyses for C,N,P, and S on the remaining priority cores collected in the SW coast area by Wingard and others. Results will be included in the existing SW Coast Geochemical Database. This database also includes nutrient data from upstream (Shark Slough and Big Cypress National Preserve), and nutrient, sulfur, and mercury biogeochemistry collected in the SW coastal area, as part of the Linking Land, Air and Water Management in the Southern Everglades and Coastal Zone to Water Quality and Ecosystem Restoration project (Orem and Krabbenhoff). The Open-File Report begun in FY07 will be completed (corrections and Director’s Approval). Data, figures, interpretations, and text will also be contributed toward publication of a journal article on the SW Coast paleoecology (Wingard et al.)
The approach we are taking is to examine the historical record of nutrients from dated sediment cores. Results will also be compared to water flow records to determine if known changes in the water control system of south Florida may correspond to distinct nutrient changes within the cores. Historical changes in sulfur geochemistry of the cores will also provide information on historical changes in salinity related to construction of canals within the Everglades. Work conducted on this project will link to work being conducted in the Integrated Biogeochemical Studies in the Everglades project (Orem and Krabbenhoff), which includes: (1) studies of nutrients, sulfur, and mercury geochemistry in upstream areas of Shark Slough and Big Cypress National Preserve, and (2) studies of nutrient, sulfur and mercury biogeochemistry in the SW coastal area (Florida Bay to Rookery Bay). Results will be compiled with faunal and floral data from the project in order to reconcile the timing of changes in nutrient input to that of changes in the biological community, and to permit determination of whether eutrophication of the coastal zone and changes in biota are directly linked.
Splits of the <63-micron fraction from selected cores will be analyzed for nutrient history studies. Results from 210Pb and 137Cs dating of these cores, and paleoecological studies will be available for comparison to the nutrient data. Once cores are collected and processed, nutrients will be analyzed from selected 2-cm intervals for TC, OC, TN, and total S using a Leco elemental analyzer available in USGS biogeochemistry labs (Orem) in Reston, VA. TP content will be analyzed using a standard geochemical method involving baking at 550?C, extraction in acid, and colorimetric analysis. All equipment for this procedure is also available at USGS labs in Reston. Organic geochemical studies will involve the use of published methods. These methods involve soxhlet extraction of biomarkers from sediments, isolation procedures involving column chromatography, and identification and quantification using GC and GC/MS. All organic geochemical equipment and instrumentation needed from this work is available in lab facilities at the USGS in Reston, VA. All geochemical data will be plotted down-core, and compared to results of other tasks. Accumulation rates for TC, OC, TN, TP, and total S will be calculated using sediment accumulation rates calculated from 210-Pb dating and the concentrations of these chemical species in the sediments. Accumulation rates for these elements in Taylor Slough and the C-111 Basin, and eastern Florida Bay have already been published by Orem. Comparison of accumulation rates in Biscayne Bay, Florida Bay, and the SW coast cores may provide additional insights into processes and flow patterns
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