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projects > paleosalinity as a key for success criteria in south florida restoration > work plan
Project Work Plan
Greater Everglades Science Program: Place-Based Studies
Project Work Plan FY 2003
A. GENERAL INFORMATION:
Project Title: Paleosalinity as a Key for Success Criteria in South Florida Restoration
Other Investigator(s): Charles Holmes
Project Summary: The most critical issue in the Central Everglades Restoration Plan (CERP) is to restore more natural patterns of freshwater flow through the terrestrial ecosystem and into the estuaries and coastal areas. Restoring natural flow includes the timing, delivery, quantity and quality of the water; in other words, "getting the water right." 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. Seasonality of water delivery is critical to the reproductive cycles of many of the organisms within the environment. This study is designed to develop and test a methodology for determining the natural patterns of change in freshwater flow and the sources of input (precipitation, groundwater, or surface flow) by conducting biochemical analyses on the tests of calcareous organisms (mollusks and ostracodes). These organisms preserve the effect of annual and seasonal salinity changes and other data about the water in which they live, and analyses of the individual growth bands of mollusks will allow detailed comparisons of seasonal change over time. Shells analyzed from radiometrically-dated sediment cores taken throughout the region allow reconstruction of seasonal salinity variations and sources of freshwater in the past, prior to significant human alteration of the system. These data will provide the resource managers (SFWMD, ACOE and ENP) with restoration targets and performance measures that will allow them to "get the water right."
Project Objectives and Strategy: There are three primary objectives to this project. 1) Test and develop a methodology for extracting water chemistry data from selected calcareous shelled animals that grow within the water. 2) Develop an understanding of the biology of the selected organisms so that the water chemistry data extracted from their shells can be put into temporal context. 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.
Metal calcium ratios in the calcium carbonate tests of estuarine and marine organisms are a function of salinity and temperature (Chave, 1954; Chivas, et al., 1983; Dwyer, et al., 1995), and ratios of stable isotopes of carbon and oxygen are indicators of sources of freshwater influx (Swart, et al., 2001). This project is developing the methodology for extracting these data from sequential growth bands in selected mollusks in order to reconstruct seasonal patterns of change in salinity and freshwater influx in south Florida. The molluscan data will be compiled with data from a species of adult ostracode, which provides a snapshot of salinity at the onset of the rainy season; combined these data will provide a powerful tool for reconstructing seasonal and annual salinity variations in the past.
A comparison of instruments (sensitive high resolution ion microprobe (SHRIMP), laser ablation ICPMS, and electron microprobe) has been completed in FY02 and the electron microprobe has been selected for the elemental analyses of the shells. Ease of use and cost effectiveness were the deciding factors in selecting the electron microprobe. The best instrument for conducting the stable isotopic analyses will be determined by the end of FY02. The focus organism is a relatively thick-shelled clam, Chione cancellata. Chione was selected as the initial test organism for several reasons: 1) the thickness of the shell makes sectioning and analyses of individual layers easier; 2) early salinity tolerance experiments have demonstrated that this clam will survive in a wide range of salinities (10-68 ppt); and 3) field evidence suggests it is one of the longer lived (3-7 years) molluscs present in Florida Bay.
The next step in developing the methodology is to complete the calibration of the Chione biochemistry to water chemistry. Field and laboratory growth experiments are being conducted on Chione for two purposes: 1) to have animals grown under documented conditions for calibrating water chemistry to shell chemistry; and 2) to determine whether the animal only adds shell material at certain times of the year or under certain environmental conditions. The information on animal growth patterns will allow us to place the water chemistry data obtained from individual growth layers into the proper temporal context. As analyses and experiments on Chione proceed, we are investigating the application of other molluscan species to this methodology to expand the utility of the tool.
Once calibration is complete, Chione will be extracted from radiometrically dated cores collected at strategic sites in Florida Bay. Molluscan shell chemistry and ostracode shell chemistry data from the cores will be compared to the monthly rainfall records in the early 20th century (available from NOAA) to determine the salinity ranges expected following given monthly rainfalls for specific sites prior to significant alteration of natural flow patterns. Stable isotope ratios and the variability in salinity from site to site will be used to differentiate sources of freshwater input.
Potential Impacts and Major Products: In order for the ACOE and SFWMD to develop a hydrodynamic model of flow and to restore natural flow to the greater Everglades ecosystem, an understanding of seasonal patterns of flow and sources of freshwater prior to alteration of the system is necessary. This project directly addresses CERP task 3006-3 (CESI CE-3) - linking hydrodynamic models of Florida Bay to nearshore areas and inflow - by providing data on natural seasonal flow and water sources to the modelers. The methodology, once developed, will ultimately address other restoration tasks, especially those related to salinity flows into Biscayne (CERP 3006-1 and 3006-7; CESI CE1) and the southwest coast (CERP 3006-6, CESI CE3). The retrospective data provided by the core analyses will document seasonal salinity changes over the last 100-200 years at specific sites. These historical data can provide target salinities and answer questions such as "what should the salinity be at the mouth of Taylor Creek given a specific amount of rainfall." These data can serve as performance measures for successful restoration in terms of restoring a natural link between monthly rainfall and freshwater influx into the estuarine systems, an essential component of restoration.
Data and information will be made available in report format, online at our web site (http://sofia.usgs.gov/flaecohist/) and through meetings and talks with client agencies. Fact sheets will be produced to explain the methodology to our clients and to the general public. Peer-reviewed papers will follow, detailing the methodology and the seasonal salinity history from selected sites within Florida Bay.
Cooperators and Collaborators:
B. WORK PLANTitle of Task 1: Calibration of molluscan shell chemistry to water chemistry
Task Funding: PBS
Task Summary and Objectives: 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. 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: In FY03 we will complete the calibration of Mg/Ca in Chione shells to the salinity of the water by conducting additional analyses on multiple specimens grown under the same water conditions, including paired valves from a single individual. These data will be used to calculate confidence levels on our interpretations of salinity based on shell chemistry. The analyses will include specimens collected in the field in August of FY02; some of these specimens have been in the habitats (see task 2) since winter of 2001. The location of the habitats in close proximity to a water monitoring station will allow us to reconstruct the water chemistry for that site. The data from the water monitoring station will be compared to our analyses of the shell layers added since winter of 2001. The results of this comparison will allow us to calibrate shell chemistry to water chemistry and provide us with a picture of what seasonal variations will look like in the shell record, a critical piece of our down-core analyses (task 3). Multiple shells from our controlled salinity and temperature tanks in the lab also will be analyzed. These data will provide us with the ability to distinguish the role of salinity versus temperature in controlling the Mg/Ca ratio, and will allow us to calculate confidence levels associated with salinity and temperature values based on shell chemistry.
Analyses of stable isotopes of oxygen and carbon will begin in FY03 and will be closely linked to work conducted by Peter Swart (U. Miami) on the Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay Project (Wingard, project leader). Once calibration tests on Chione are successfully completed, we will begin to experiment with other molluscan species. Chione have not been found alive in modern Florida Bay in the northern transition zone (although they are present in cores), so we want to identify a good indicator species for the critical northern transitional zone. Also, Mercenaria and Periglypta, both in the family Veneridae like Chione, may be examined for their utility in monitoring the more open marine and reef environments.
Planned Outreach: Results of the calibration studies will be presented to our colleagues and client agencies through talks and posters at meetings. Data and information will be made available in report format, online at our web site (http://sofia.usgs.gov/flaecohist/). Fact sheets will be produced to explain the methodology to our clients and to the general public. Peer-reviewed papers will follow, detailing the methodology.
Task Summary and Objectives: 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.
Work to be undertaken during the proposal year and a description of the methods and procedures: 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). These experiments will continue in FY03, and throughout the length of the project to gather data on the life span, reproductive patterns, and environmental factors that affect these animals. In FY03, we may add additional species of molluscs to begin the process of identifying other indicator species. 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. An experiment begun in FY02 is monitoring growth under different salinities (15, 25, 35 and 45 ppt) and different temperatures (15, 25, 35 degrees C). These experiments will continue in FY03 with additional variables and species being tested. 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.
In FY03 we will attempt to design laboratory and/or field experiments to test the relationship between the stable isotopic signature in the shell (especially Carbon) and the isotopic composition of the water.
Planned Outreach: Results of the growth studies will be made available in report format, online at our web site (http://sofia.usgs.gov/flaecohist/). Fact sheets and presentations for our clients will put the growth studies within the context of providing temporal information on the salinity and water source data extracted from the shells. Peer-reviewed papers will follow, relating the growth studies to shell chemistry analyses. Additional biological papers will be generated, presenting the results of the growth studies and our findings on the role of environment in reproduction, ontogeny and mortality of the organisms studied.
Task Status (proposed or active): Active
Task Summary and Objectives: 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.
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.
Work to be undertaken during the proposal year and a description of the methods and procedures: Cores from Dragover, Russell, Whipray and Rankin have been collected, processed, and sorted for standard faunal analyses. Specimens of Chione cancellata have been selected for sectioning and analysis. Work in FY03 will focus on analyzing these specimens for metal-calcium ratios (salinity) and stable isotopes (water sources). If additional molluscan species have been identified in tasks 1 and 2, these also will be analyzed. These data will be compiled with data on ostracode shell chemical analyses for verification and calibration of the salinity curves obtained from the molluscs.
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). Ostracode analyses on the cores, begun in FY 02, will be completed in FY02 and the data compiled with the molluscan data.
Molluscan and ostracode biochemical data will be plotted and compared to general downcore assemblage analyses already completed on three of the cores to look for patterns of change in seasonal, annual and decadal scale trends in salinity and sources of freshwater input over the last 100-200 years at these sites within Florida Bay. A comparison of the results from eastern and central Florida Bay will highlight any geographic variations in salinity and freshwater influx that existed prior to drainage alteration and allow comparison to the present day situation. By comparing these data to early 20th century rainfall records (available from NOAA), we can determine what salinity ranges were following a given period of monthly rainfall, prior to significant alteration of natural flow. The next step is to forecast what the salinity should be under restored "natural" flow following given amounts of rainfall. These data provide specific targets for restoration and for water management practices.
Planned Outreach: Data and information will be made available in report format, online at our web site (http://sofia.usgs.gov/flaecohist/) and through meetings and talks with client agencies. Fact sheets will be produced to explain the methodology to our clients and to the general public. Peer-reviewed papers will follow, detailing the methodology and the seasonal salinity history from selected sites within Florida Bay.
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