Study Title: Paleosalinity as a Key for Success Criteria in South Florida Restoration
Study Start Date: 10/01/2000 Study End Date: 9/30/05
Web Sites: http://sofia.usgs.gov/flaecohist/
Location (Subregions, Counties, Park or Refuge): Everglades National Park, Monroe County
Funding Source: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Other Complementary Funding Source(s):
Principal Investigator(s): G. Lynn Wingard
Study Personnel: Thomas Cronin; Chuck Holmes; James Murray; Robert Stamm; US Geological Survey. Gary Dwyer, Duke University
Supporting Organizations: South Florida Water Management District; Everglades National Park
Associated / Linked Studies: Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area; and Synthesis of South Florida Ecosystem History Research Projects

Overview & Objective(s):

There are three primary objectives to this project. 1) Develop a high resolution methodology to analyze the variability in shell chemistry of select marine/estuarine organisms as a proxy to changes in water quality and source. 2) Develop an understanding of the biology of the selected organisms such that the variations in shell chemistry may more accurately reflect the temporal and spatial variability of both water quality and source. 3) Apply this technique to shells found in sediment cores that span the last 100-300 years of South Florida history in order to determine the seasonal variation in salinity and water sources prior to significant human alteration of the environment. These data will provide resource managers with the necessary information to establish targets and performance measures as restoration of more natural timing and delivery of water proceeds.

Specific Relevance to Major Unanswered Questions and Information Needs Identified: (Page numbers below refer to 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 goal of the Paleosalinity study is to develop a high resolution method for interpreting short term (less than a decade) changes in salinity from calcareous organisms preserved in cores dating back 100-500 years. The results of this work are applicable to all USGS ecosystem history studies. Specifically this study supports the Florida Bay and Florida Keys Feasibility Study Project and the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study Project, and it provides information relevant to the Combined Structural and Operational Plan (CSOP) and Landscape Modeling projects. This study supports these projects by 1) developing a tool that can be used to understand the predrainage hydrology, including the amount, timing and seasonality of freshwater delivered historically; and 2) providing modelers with data on historic conditions in order to set targets and performance measures that reflect natural hydrologic patterns.

This study supports the Florida Bay and Florida Keys Feasibility Study Project by addressing the questions 1) What are the links between impediment to circulation created by the causeway and the ecology of Florida Bay . . .?" (DOI Science Plan, p. 64), "What are the links between freshwater inflows to Florida Bay and the ecology of the bay?" (p. 65), and "What is the ecological response to hydrologic change?" (p. 66).

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 . . . Taylor Slough . . . prior to drainage and modification . . ." (DOI Plan p. 63), "What are the hydrologic targets needed to mimic historic flows . . . ? (p. 63).

Status: Progress has been made in four general areas. 1) Calibration of ostracode Mg/Ca ratios to instrumental salinity (Robblee, unpublished data) readings has shown that ostracode Mg/Ca can accurately predict salinity to within 1-4ppt. Additional modern work on calibration of ostracode shells to water chemistry has been completed in association with the Biscayne Bay study and a report prepared. 2) Experimental work on molluscan shell chemistry and growth is continuing. Successful growth of Chione shells under known water conditions has been achieved both in the lab and the field; these shells and their associated water chemistry are currently being analyzed. Additional molluscan experiments are being conducted that a) use Sr as a marker to tag the shell for growth and water chemistry measurements, b) test growth, and c) test tolerances of common south Florida mollusks to salinity, temperature, and nutrient loads. These experiments supplement our field observations to provide a more complete proxy data set for all ecosystem history studies. 3) High resolution, semi-quantitative electron microprobe analyses have been completed on ten Chione specimens. Eight of these specimens are from Florida Bay field habitats, and two from controlled laboratory aquaria systems. 4) A statistical method of deriving a single salinity value from molluscan percent abundance assemblage data has been developed and compared to instrumental readings. With additional experimental data on molluscan salinity tolerances (developed under item 2) this statistical method will enhance accuracy of salinity estimates from cores.

Recent Products: A summary chapter on the Ecosystem History of Florida Bay, with the emphasis on Paleosalinity was generated for the Florida Bay PMC synthesis and has been reviewed for publication in an FMRI bulletin.

Planned Products: Open file reports on a) the molluscan salinity and temperature tolerance experiments and b) the shell chemistry analyses will be completed in Fall 04, along with companion fact sheets summarizing the work. Also, an OFR summarizing significant field observational data on mollusks will be completed in FY05. Once experimental work is completed a journal article will be compiled.

WORK PLAN

Title of Task 1: Calibration of molluscan shell chemistry to water chemistry
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: G. Lynn Wingard
Phone: 703-648-5352
FAX: 703-648-6953
Task Status (proposed or active): Active
Task priority: High
Time Frame for Task 1: 10/2000 to 9/05
Task Personnel: J.B. Murray, R. Stamm, G.L. Wingard

Task Summary and Objectives:

Restoring more natural patterns of freshwater flow through the terrestrial ecosystem and into the estuaries and coastal areas is one of the most critical issues to restoration of south Florida ecosystems. Restoring natural flow includes the timing, delivery, quantity and quality of the water. In order to recreate natural freshwater flow patterns, it is essential to understand the natural patterns of variation prior to significant human alteration of the system and the natural sources of water. This task is designed to develop a method for extracting seasonal data from hard-shelled organisms, but there are many tests that need to be performed. This task is the first step in designing the method.

The objectives of this task are to 1) determine the best methodology for extracting biochemical information from individual shell layers (accomplished in FY02) and 2) to calibrate the chemical information in the shell to the chemistry of the water in which the animal grew (in progress in FY03). We must demonstrate that we can accurately predict water chemistry and composition based on molluscan shell chemistry. In order to accomplish this, we will analyze shell material grown under known water conditions (both in the field and in the lab) to determine if documented shifts in water conditions (salinity, temperature, freshwater influx) produce a recognizable chemical signature. Multiple shells grown under the same conditions will be analyzed to be certain the results are reproducible and that all members of the species "record" information in the same way. In the laboratory, we will grow individuals under controlled conditions (task 2) in order to isolate the chemical signal produced by different environmental variables (for example, temperature versus salinity). Task 1 and task 2 will be carried on concurrently and together will provide the data and techniques that will allow us to apply this tool to shells extracted from cores (task 3).

We must demonstrate that we can accurately predict water chemistry and composition based on molluscan shell chemistry. In order to accomplish this, we will analyze shell material grown under known water conditions (both in the field and in the lab) to determine if documented shifts in water conditions (salinity, temperature, freshwater influx) produce a recognizable chemical signature. Multiple shells grown under the same conditions will be analyzed to be certain the results are reproducible and that all members of the species "record" information in the same way. In the laboratory, we will grow individuals under controlled conditions (task 2) in order to isolate the chemical signal produced by different environmental variables (for example, temperature versus salinity). Task 1 and task 2 will be carried on concurrently and together will provide the data and techniques that will allow us to apply this tool to shells extracted from cores (task 3).

Work to be undertaken during the proposal year and a description of the methods and procedures:

Final compilation of research results on calibration of molluscan shell chemistry to water chemistry will take place in FY05. A report summarizing the calibration results will be completed. If time and funding allows, we will attempt to complete the stable isotope portion of the study.

The purpose of task 1 is to derive data for application in task 3, and therefore does not directly address information needs or unanswered questions without the application of the results in task 3. However, it is a critical component, when combined with results from task 2 and 3, in addressing the "Major Unanswered Questions and Information Needs" as discussed in detail in the project overview above.

Specific Task Product(s):

Open file report on the molluscan salinity and temperature tolerance experiments will be completed in Fall 04, along with a companion summarizing the work. Also, an OFR summarizing significant field observational data on mollusks will be completed in FY05. Once experimental work is completed a journal article will be compiled.

Title of Task 2: Establishing rates and requirements for molluscan shell accretion
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: G. Lynn Wingard
Phone: 703-648-5352
FAX: 703-648-6953
Task Status (proposed or active): Active
Task priority: High
Time Frame for Task 2: 10/2000 to 9/05
Task Personnel: J.B. Murray, R. Stamm, G.L. Wingard

Task Summary and Objectives:

Information on seasonal changes in water supply and sources of water prior to water management practices is critical for successful restoration. The goal of this project is to develop a methodology for utilizing incremental growth layers in shells in order to reconstruct past changes in salinity and water quality on a seasonal basis. In order to accomplish these goals, however, we need to understand the ecological constraints that affect shell accretion. Published studies of the environmental and vital effects on shell accretion are rare, and rates of accretion will differ from species to species. This task will address this information gap.

The objective of this task is to understand how vital effects and autoecologic factors affect the accretion of molluscan shell material. Without this understanding, the shell biochemical data obtained in task 1 cannot be placed in the proper temporal or environmental context. It is essential to know the answers to the following questions. 1) Does the animal grow throughout the year? If it does not, then the variations seen in the shell chemistry will not be a reflection of seasonal changes throughout the year. 2) Does the animal have certain temperature or salinity constraints on growth? If it only adds shell material within a narrow salinity range for example, then the shell "recorder" will be "turned off" at critical salinity extremes that are important to document for this methodology to be successful. 3) Does the animal fractionate carbon isotopes? If yes, we need to establish the relationship between the shell ratios and the water ratios (this is related to task 1 - calibration of shell chemistry to water chemistry). These questions can be answered by carefully documenting growth under a series of controlled experiments and in habitats constructed in the field. Animals grown under these controlled conditions provide data to document when and how shell accretion occurs, and once growth is documented, the animal can be used in task 1 to calibrate shell chemistry.

In order to determine natural growth rates and species responses to environmental stressors and seasonal variations, Chione have been placed in habitats in Florida Bay near working water-monitoring stations beginning in January 2001. The in-situ variables of salinity, temperature, rainfall, etc. can be documented using the data from the water monitoring stations and our instrumentation. The habitats are periodically pulled and the animals digitally photographed to document growth. Dead specimens are removed and replaced with live individuals. Both living and dead specimens that show growth are periodically removed and are used in the calibration tests (task 1). By continuing these experiments over a period of years, we capture data on seasonal changes and how the organism records these data biochemically within its shell. These data allow us to more accurately interpret the patterns we see in the shells (task 1) and ultimately the downcore data (task 3).

In order to monitor change on a weekly basis, and to establish controlled water conditions in which to test the organism's response to specific environmental variables, we have set up a series of tanks in the laboratory in Reston. The main growth tanks are kept at normal marine salinities and duplicate the in-situ habitats of Florida Bay as close as possible. These tanks act as a control and provide data for comparison against seasonal variation in growth seen in the habitats in Florid Bay. The water chemistry within all the tanks is monitored for multiple factors including; salinity, temperature, nitrate level, dissolved oxygen, ORP, etc. Additional experimental tanks have been set up to isolate the effects of a single variable on shell accretion and the resulting biochemical signature. These tanks will also be "pulsed" with micronutrients such as strontium and magnesium to create a dated marker in the shell layers. These experiments will provide us with the data essential to understanding and interpreting the analytical results from task 1 and will provide specimens grown under controlled conditions to be used for calibration in task 1.

Work to be undertaken during the proposal year and a description of the methods and procedures:

Final compilation of research results on growth experiments will take place in FY05 and data will be compiled in cooperation with Florida Gulf Coast University. A report summarizing the molluscan data will be produced.

The purpose of task 2 is to derive data for application in task 3, and therefore does not directly address information needs or unanswered questions without the application of the results in task 3. However, it is a critical component, when combined with results from task 1 and 3, in addressing the "Major Unanswered Questions and Information Needs" as discussed in detail in the project overview above.

Specific Task Product(s):

Open file reports on the shell chemistry analyses will be completed in Fall 04, along with a companion fact sheet summarizing the work. Once experimental work is completed a journal article will be compiled.

Title of Task 3: Application of schelerochronology to interpretation of seasonal salinity patterns in Florida Bay
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: G. Lynn Wingard
Phone: 703-648-5352
FAX: 703-648-6953
Task Status (proposed or active): Active
Task priority: High
Time Frame for Task 3: 10/2000 to 9/05
Task Personnel: J.B. Murray, R. Stamm, G.L. Wingard

Task Summary and Objectives:

In order to restore more natural conditions for Florida Bay, restoration managers need to understand what the conditions were like prior to significant human alteration of south Florida. Knowing the amount, timing, and sources of freshwater influx in the past is critical, if those conditions are to be reproduced. The purpose of this project is to develop a tool for measuring seasonal changes in salinity, water quality and water sources in the past. Once that tool is developed, we can apply the method to interpretation of shell material in well-dated cores from environments throughout south Florida. These data will provide answers to questions such as "did hypersalinity bulls-eyes exist in the past?" and "did salinity at the mouth of Taylor Creek fluctuate dramatically from wet to dry seasons?".

The objective of this task is to apply the methodology developed in tasks 1 and 2 to document seasonal variation in Florida Bay over the last 100-200 years. These data will provide the resource managers and modelers with data on past conditions in order to "get the water right". Well preserved molluscan shells from radiometrically dated sediment cores collected at strategic locations within Florida Bay will be analyzed following the methods developed in tasks 1 and 2 and these data will be compiled with ostracode biochemical analyses to reconstruct seasonal and annual salinity variations in the past.

Well preserved molluscan shells from radiometrically dated sediment cores collected at strategic locations within Florida Bay will be analyzed following the methods developed in tasks 1 and 2 and these data will be compiled with ostracode biochemical analyses to reconstruct seasonal and annual salinity variations in the past.

Influx of freshwater from the terrestrial Everglades into eastern Florida Bay plays a significant role in controlling salinity, along with direct rainfall (McIvor, 1994). Salinity surveys indicate a discrete freshwater plume moves southward from Taylor Slough into the basin south of Little Madeira Bay during periods of high flow. Cores from Dragover Bank and Russell Bank should provide data to document historical seasonal changes in salinity and freshwater supply to eastern Florida Bay. Areas of central Florida Bay have experienced hypersaline conditions since at least the 1980's. These basins fall within the "flow shadow", receiving little terrestrial influx of freshwater and little marine influx as well. Precipitation and evaporation are the dominant factors affecting salinity in this portion of the Bay. A critical question for restoration is whether these episodes of hypersalinity are a result of water management practices, or whether they are a natural phenomenon. Cores from Whipray Basin and Rankin Basin have been collected and standard faunal abundance analyses have been conducted. The preliminary indications are that Rankin Basin received significantly more freshwater influx in the past. This task will utilize biochemical analyses of molluscs (task 1 and 2) and ostracodes to determine the seasonality of salinity changes and the sources of freshwater influx from the period prior to alteration of natural flow through the present, in order to provide managers and modelers with the necessary data for restoration targets and performance measures.

Ostracodes molt as they proceed through various growth stages throughout the year. The adult test represents an essentially instantaneous secretion recording the salinity and temperature at that point in time. The Ca/Mg will be determined for ostracode tests by direct current plasma atomic emission spectrophotometry (DCP). The ostracode Loxoconcha matagordensis grows adult carapaces largely in the late spring and early summer (primarily June). These specimens therefore record the salinity at the typical onset of the rainy season. The timing onset of the rainy season and the extent of the initial drop in salinity are excellent indicators of the climatic patterns for the entire year (particularly in determining an El Niño or La Niña event).

Work to be undertaken during the proposal year and a description of the methods and procedures:

Final compilation of analyses of molluscan shell chemistry will be completed in FY05 and compared to molluscan assemblage data, historical salinity and rainfall records, and other available data.

If the methodology proves sound, then we will be able to apply the results from tasks 1 and 2 to interpretation of faunal remains in dated cores collected in Florida Bay. These data can be used to "ensure that hydrologic performance targets accurately reflect the natural predrainage hydrology and ecology" (DOI Science Plan, p. 14). Specifically this task supports the Florida Bay and Florida Keys Feasibility Study Project and the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study Project, and it provides information relevant to the Combined Structural and Operational Plan (CSOP) and Landscape Modeling projects. (See detailed discussion in project overview above.)

Specific Task Product(s):