projects > historical changes in salinity, water quality and vegetation in biscayne bay > work plan
Project Work Plan
Greater Everglades Science Program: Place-Based Studies
Project Work Plan FY 2003
A. GENERAL INFORMATION:
Project Title: Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay
Other Investigator(s): Charles Holmes
Other Investigator(s): Gary Dwyer
Other Investigator(s): Scott Ishman
Other Investigator(s): Evelyn Gaiser
Project Summary: During the last century, Biscayne Bay has been greatly affected by anthropogenic alteration of the environment through urbanization of the Miami/Dade County area and alteration of natural flow. The sources, timing, delivery, and quality of freshwater flow into the Bay, and the shoreline and sub-aquatic vegetation have changed. Current restoration goals are attempting to restore natural flow of fresh water into Biscayne and Florida Bays and to restore the natural fauna and flora, but first we need to determine pre-alteration baseline conditions in order to establish targets and performance measures for restoration. This project is designed to examine the natural patterns of temporal change in salinity, water quality, vegetation, and benthic fauna in Biscayne Bay over the last 100-300 years and to examine the causes of change.
Project Objectives and Strategy: The objectives of this project are to examine in broad context the historical changes in the Biscayne Bay ecosystem at selected sites on a decadal-centennial scale, and to correlate these changes with natural events and anthropogenic alterations in the South Florida region. Specific emphasis will be placed on historical changes to 1) amount, timing, and sources of freshwater influx and the resulting effects on salinity and water quality; 2) shoreline and sub-aquatic vegetation; and 3) the relationship between sea-level change, onshore vegetation, and salinity. In addition, a detailed examination of historical seasonal salinity patterns will be derived from biochemical analyses of ostracodes, foraminifera, molluscs, and corals. The corals will allow us to compare marine and estuarine trends, examine the linkage between the two systems, and will provide precise chronological control. Land management agencies (principally SFWMD, ACOE and Biscayne NP) can use the data derived from this project to establish performance criteria for restoring natural flow, and to understand the consequences of altered flow. These data can also be used to forecast potential problems as upstream changes in water delivery are made during restoration.
The strategy for FY 03 is to focus on analyzing the sediment cores collected in FY02 in Biscayne Bay under an OFA with SFWMD. Sampling and analyses of selected cores will follow methods established by the Florida Bay Ecosystem History Projects (Brewster-Wingard, USGS, GD; Orem, USGS, GD). Cores will be dated using Pb-210 geochronology and C-14 where appropriate (Holmes, USGS, GD). Preliminary radiocarbon dating suggests the uppermost 200 cm at these sites represent between 400 and 1500 years of sediment accumulation, thus we will be able to obtain decadal to centennial environmental records. These long-term records will allow reconstruction of natural patterns of change prior to significant human alteration of the environment, will illustrate the impact of anthropogenic changes, and will allow us to differentiate changes due to human activity versus natural patterns of change.
Data gathered from monitoring sites will serve as proxy data for interpreting the downcore faunal and floral remains. Data from 28 sites in Florida Bay (collected 2X/year beginning in 1995 will be utilized). Modern monitoring sites will be established in Biscayne Bay in FY03 (8-15 sites) in cooperation with Barbara Lidz's Chemical Pollutants and Toxic Effects on Benthic Forams, Biscayne Bay Project (USGS). A series of downcore geochemical analyses will evaluate past changes in nutrients (C,N,P,S), shell geochemistry (salinity and temperature), and stable isotopes (salinity and sources of water). The analyses of the indicator-species and the shell geochemistry work will be an extension of ongoing and completed ecosystem history work in Florida Bay that has focused on historical salinity patterns (Cronin, Brewster-Wingard, and others).
Stable isotopic data from water samples will be analyzed (P. Swart, U. Miami) to determine the origin of variations in salinity in Biscayne Bay. Freshwater from precipitation, runoff and groundwater have unique O and H isotopic signatures, so the sources of freshwater influx can be traced. These data are essential in assessing the impact of water management practices on the Bay and the input of groundwater into the system. This method was developed in Florida Bay, utilizing samples collected since 1993, and will now be applied to Biscayne Bay.
Potential Impacts and Major Products: The Comprehensive Everglades Restoration Plan (CERP) and the Critical Ecosystem Studies Initiative (CESI) have both identified the importance of understanding freshwater flow into Biscayne Bay and the changes incurred due to alterations in flow.
This project directly addresses CESI Task CE1 and CERP Task 3006-7: to "conduct isotopic/paleoecologic studies for the determination of historical salinities/freshwater flows for Biscayne Bay." Data provided also will contribute to CESI Tasks EP1, CE2, and LP2 and CERP Tasks 3007-2, 3007-3, 3050-4 and 3050-5 by contributing to the understanding of the relationships between salinity and the health and distribution of sub-aquatic vegetation and fauna. Tracking changes in onshore vegetation over time will contribute to CESI Task EP1 and CERP Task 3007-9 and data on historical changes in nutrient supply will contribute to CESI Task WQ3 and CERP Task 3090-4. The data provided by this project will evaluate the potential impacts of restoration changes and will provide targets for restoration of historical flow. This will allow the Army Corps of Engineeers (ACOE), the South Florida Water Management District (SFWMD) and other agencies responsible for guiding CERP and CESI to make informed decisions that will protect Biscayne Bay and Biscayne National Park. Part of this research is already funded by an OFA with SFWMD (Richard Alleman, contact).
Data on individual cores and modern monitoring work will be made available online immediately following completion of analysis at the Ecosystem History Project website http://sofia.usgs.gov/flaecohist/ and the University of Miami stable isotope web site http://mgg.rsmas.miami.edu/groups/sil/index.htm. The University of Miami site also will release oxygen, hydrogen, and carbon isotopic data on South Florida coastal waters collected since 1993. Open-file reports on each core and a synthesis article for a scientific journal will be compiled. A special publication highlighting the research would be prepared for a non-scientific audience, including the stakeholders and the public, and could be made available at Biscayne NP. In addition, results will be reported at scientific meetings, and to client agencies.
Cooperators and Collaborators:
B. WORK PLAN
Task Status (proposed or active): Active
Task Summary and Objectives: The initial and primary task is to determine the age of the selected cores, the general salinity history, the presence of sub-aquatic vegetation (SAV), and the probable abundance of SAV using established geochronologic and paleoecologic methods. This task lays the groundwork for additional analyses as well as providing necessary data for the final interpretation of the cores. The purpose of the overall project is to determine the changes in water quality and salinity over time, and the corresponding changes in onshore and sub-aquatic vegetation. The first step is to determine if the core has a good chronology (i.e. the core has not been disrupted) and if it contains faunal remains for analyses. If the core meets these criteria, then additional work can proceed. If the chronology is not good, or if there are no preserved fauna, than another core will be selected and the tasks repeated until we identify a core that meets these criteria. The chronologic data will be used to interpret all additional analyses. Paleoecological methods also will be used to provide data on the general trends within the core in terms of salinity, SAV, and changes in water quality and nutrient supply.
Work to be undertaken during the proposal year and a description of the methods and procedures: Six cores were collected at three sites in FY02 (Card, "No Name", and Featherbed Banks). FY03 project work will focus on completion of the analyses of these cores begun in FY02. Faunal samples are processed using standard methods and all fractions are retained for analyses. A portion of the less than 63-micron fraction is used for Pb-210 geochronology and selected shells or plant material will be used for radiocarbon dating. The greater than 63-micron fraction is sorted for faunal analyses; ostracodes, molluscs and benthic forams are picked, sorted and identified. A small portion of core material is retained and processed for diatoms (Gaiser, FIU). Percent abundance is calculated for the faunal and diatom data, and these data are compared to data from 28 sites in modern Florida Bay where faunal and floral associations have been studied between 1996-2000 and to sites established in Biscayne Bay (see work listed in Task 2). These modern data serve as proxies for interpreting the down-core data. The down-core faunal and floral assemblages and the presence or absence of key indicator species allow interpretation of trends in salinity, water quality and the presence of SAV at the core sites.
In the second half of FY03, additional cores will be collected. Determination of sites will depend on results from analyses of FY02 cores and will be discussed with the client agencies (SFWMD, NPS-BB, ACOE).
New cores will be described, x-rayed, and cut into 2-cm intervals for processing. Samples will be processed using standard methods and all fractions will be retained for analyses as described above for FY02 cores.
Planned Outreach: Data from cores will be compiled, analyzed, and presented as a poster or talk at conferences and meetings with clients. Additionally, all data will be made available on line at http://sofia.usgs.gov/flaecohist/. This web site provides links to data, posters and open-file reports produced by the South Florida Ecosystem History Projects. Open File Reports will be produced on the cores and distributed to the clients and cooperators. After the analyses of several cores have been completed, a journal article for a scientific publication will be produced and a glossy USGS special publication that would highlight the research for the stakeholders. The audience for this special publication would be the non-scientists among the stakeholder agencies (NPS, ACOE, SFWMD) and the general public via NPS.
Task Summary and Objectives: Determine salinity history of several regions in Biscayne Bay for the period prior to and during large-scale 20th century urbanization and water diversion using salinity proxies from sediment cores from Biscayne and Card Sound. Relate salinity variability to changes in fresh water flow due to land-use changes and natural variability in rainfall, freshwater runoff and water temperature (evaporation) and determine the extent to which water diversion disrupted natural patterns of salinity. Develop new method to use oxygen isotope ratios in foraminifers as proxy of past salinity and/or temperature changes. Compare and "splice" together the sediment core records of paleosalinity and paleotemperature with instrumental records of rainfall, bay salinity and temperature obtained from water monitoring. The reconstructed record of physical and biological conditions in Biscayne Bay will be compared to the history of water quality obtained by W. Orem (task 6). Biscayne Bay ecosystem and salinity history also will eventually be compared to records from Florida and Manatee Bays to examine regional trends.
Work to be undertaken during the proposal year and a description of the methods and procedures: Work in FY 2003 will involve measurement of faunal and geochemical proxies of salinity and temperature from sediment cores taken in 2002 (Card Sound Bank, "No Name" Bank, and Featherbed Bank located in central and southern Biscayne Bay) and if time permits, an additional site in northern Biscayne Bay, near the Rickenbacker Causeway (collected in 1997), will be examined. Proxy methods include 1) oxygen isotope analyses of benthic foraminifera, 2) trace elemental (magnesium/calcium ratios) of ostracodes, 3) morphological indicators of temperature (shell size), and 4) relative proportions of species of forams, ostracodes and molluscs indicative of specific salinity ranges (i.e. oligohaline, mesohaline, etc.)(related to task 1 assemblage analyses). The stable isotopic and trace elemental analyses will be carried out with cooperators using mass spectrometry and direct current plasma emission spectrometry at University of Miami and Duke University, respectively. The use of paired analyses of stable isotopes of forams and Mg/Ca ratios in ostracodes should allow the quantification of changes in salinity and temperature and the impact of these changes could then be assessed from the faunal analyses of benthos from the same samples. Selected intervals identified as representing extreme salinity conditions may also be studied for seasonal salinity variability using molluscan shell chemistry, depending on preservation in cores and status of mollusk calibration studies (related to Paleosalinity as a Key for Success Criteria in South Florida Restoration Project; Wingard, Wardlaw and others).
A transect of modern foram, ostracode, mollusk and water samples will also be collected in summer 2002 and winter 2003 for the following purposes: (1) to calibrate the oxygen isotopic composition of foraminiferal shells to water isotope ratios and salinity for application to sediment core forams; (2) to improve understanding of the salinity tolerance of indicator species in Biscayne Bay; (3) to determine the local radiocarbon "correction" for Biscayne Bay. These modern calibration sites will be located along one or more salinity transects and will be taken during summer and winter seasons. The sites will be located strategically in relation to P. Swart's (see Task 3) and G. Dwyer's water chemistry stations, and will correspond to the monitoring sites established in Task 1 for the benthic faunal surveys.
Planned Outreach:In addition to reports listed in Task 1, the following will be done: presentations to Biscayne National Park personnel and South Florida Water Management District, write Fact Sheet, summarize results for modeling community.
Task Summary and Objectives: This task is designed to answer the question of whether variations in salinity, a common feature of the coastal environments of Biscayne, are a result of terrestrial runoff, ground water input, or local precipitation. By analyzing stable oxygen and hydrogen isotopes in the water we can determine whether the source of freshwater influx is from rainfall, overland flow, or groundwater input. This information is vital in assessing (i) the impact of water management changes within the terrestrial Everglades on the coastal ecosystem, (ii) the input of groundwater into the coastal systems, and (iii) identifying which systems are susceptible to anthropogenic water use decisions.
Isotopic tracers have been successfully used in Florida Bay. The technique works because although groundwater, surface water and precipitation all have essentially zero salinity, they have different oxygen, hydrogen, and carbon isotopic compositions, which are a result of evaporation, degradation of organic material and interaction with local rocks. Since 1993 samples collected by SERC at FIU in Florida Bay have been analyzed for their stable isotopic composition (O, H, and C). In 1998, the network was expanded to include all of the samples collected by SERC on the West Coast of Florida and in Biscayne Bay. Samples were also collected from the Everglades and from rainfall at four locations. This work demonstrated that between 1993 and 1999 over 70% of the freshwater in the western portion of Florida Bay was derived from rainfall rather than runoff. The extent of freshwater runoff from the Everglades into the NE corner of Florida Bay has been clearly demonstrated. The purpose of this task is to utilize the methods demonstrated in Florida Bay to obtain data on current sources of freshwater input into Biscayne Bay that are essential for successful restoration of natural flow. These data can then be compared to downcore data gained in task 2 to determine the extent to which freshwater sources for Biscayne Bay have change over the last 100-200 years.
Work to be undertaken during the proposal year and a description of the methods and procedures: Isotopic analyses will be conducted on samples of water from 45 stations sampled monthly and eight stations sampled quarterly in Biscayne Bay, Barnes Sound, and north Florida Bay by SERP at FIU. This sampling has been carried out in conjunction with FIU since 1993. In addition we will analyze freshwater samples from the Everglades (collected by ENP) and precipitation samples from stations in Key Biscayne, Key Largo, and a new station to be installed at Biscayne Park Headquarters (operated by RSMAS). A series of groundwater wells installed by Biscayne National Park also will be sampled. These wells provide a transect from Black Point out onto the reef tract.
All samples are preserved and filtered according to conventional procedures. Fifty-five water samples per month will be analyzed for hydrogen, oxygen and carbon isotopes using mass spectrometric techniques. Data will be compiled, interpreted, and used to produce contour maps. These data will include all analyses completed between 1993 and the present day. In addition to a spatial analysis of the data, samples will be analyzed in a temporal sense and related to natural and anthropogenic changes in the South Florida Everglades Ecosystem in conjunction with results from Task 2.
Planned Outreach: Data and maps will be made available on the University of Miami stable isotope web site http://mgg.rsmas.miami.edu/groups/sil/index.htm and made available to clients and colleagues at meetings and conferences. Data from this task will contribute to final products for project, discussed under Task 1.
Task Status (proposed or active): Active (with new direction for FY03)
Task Summary and Objectives: Reconstruct vegetational trends at selected sites using pollen and seeds preserved in sediment cores. Although temporal resolution depends on sedimentation rates at core sites, vegetational changes on a decadal scale should be identifiable. Also, document fire history of region through quantitative analysis of charcoal in sediment cores.
Work to be undertaken during the proposal year and a description of the methods and procedures: Analyze pollen assemblages from cores collected for task 1 during FY02 and from marsh cores to be collected in FY03; initial examination will be at 10 cm increments, with other samples filled in as appropriate. Vegetational trends will be reconstructed through statistical comparison with database of ~200 surface samples collected in different vegetation types throughout the Everglades; secondarily, changes in hydroperiod and water depth will be estimated from vegetational proxies. Charcoal analyses will be undertaken using chemical digestion to isolate charcoal and morphometric analysis to quantify charcoal in each sample. Geochronologies established as part of task 1 will allow determination of the timing of changes in vegetation or charcoal abundance and correlation with specific environmental or anthropogenic changes.
Planned Outreach: In addition to reports listed in Task 1, presentations will be made to Biscayne National Park personnel and South Florida Water Management District, and results will be summarized for modeling community.
Task Summary and Objectives: Biscayne National Park contains the northern-most extension of the Florida Keys Reef Tract, extending from Fowey Rocks in BNP 130 miles south to the Marquesas. The Florida Reef Tract is a unique natural resource - the only reef ecosystem in the continental US and among the largest bank reef systems in the world. Yet, this unique ecosystem is threatened by "upstream" changes in freshwater flow through the terrestrial Everglades. It is critical to understand the linkages between the terrestrial system, Biscayne Bay and the Reef Tract prior to implementing substantial restoration changes. This task examines these linkages by comparing isotopic records obtained from coral to records from the near shore cores collected and analyzed in Tasks 1 and 2, and to water chemistry data collected in Task 3. In addition in provides a long term continuous record of offshore water chemistry that will provide information on the relationship of coral health to water chemistry pre- and post-alteration of terrestrial flow. If corals can be located within the Bay and permission to sample them obtained, additional comparisons can be made between offshore and Bay waters.
Work to be undertaken during the proposal year and a description of the methods and procedures: Following the methods used by Swart et al., (1996) at Alina's Reef near Elliot Key, a second reef site within Biscayne National Park will be selected and sampled at a relatively low resolution transect (5 samples per year) over a 200 year period of time. Two additional short cores will be taken at the site of the original coral sampling at Alina's Reef in 1986, allowing us to bring the record up to date and to compare the isotopic data and the instrumental records. In addition, we hope to locate and utilize corals situated within Biscayne Bay in order to compare salinity records inside and outside the Bay.
Planned Outreach: Data and results will be made available to clients and colleagues at meetings and conferences. Data from this task will contribute to final products for project, discussed under Task 1.
Task Summary and Objectives: Nutrients from agricultural and urban runoff are causing eutrophication and microalgal blooms in many of the estuaries in south Florida, including Biscayne Bay. The effects of this excess nutrient input on biotic assemblages within the estuaries, however, are not understood, but may be substantial. Eutrophication and microalgal blooms may be responsible for seagrass dieoff in Florida Bay, and coral mortality in the Florida Keys. In Biscayne Bay, seagrass dieoff, changes in microalgal population structures, and changes in other benthic species may be occurring. Linking eutrophication to these changes in the biotic community, however, is a difficult problem.
Our major objectives are to determine the historical record of eutrophication in Biscayne Bay and to evaluate the linkage between eutrophication and changes in the biotic community in the bay. The approach we will take in this task is to examine the historical record of nutrients in Biscayne Bay 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 content of the cores will also provide information on historical changes in salinity in Biscayne Bay related to construction of canals within the Everglades. We will also examine organic geochemical markers of seagrass and microbial communities in the cores to determine historical changes in these biota. These results will be compiled with faunal and floral data from tasks 1 and 2. Comparing the timing of changes in nutrient input to that of changes in the biological community will allow a determination of whether eutrophication of the estuary and changes in biota are directly linked.
Work to be undertaken during the proposal year and a description of the methods and procedures: Six cores from three sites were collected in FY02 (Task 1). Splits of the <63-micron fraction from these cores are available 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. In FY03, nutrients will be analyzed from every 2-cm interval in the cores, meeting the criteria defined in Task 1. Additional piston coring will be conducted as needed in FY03 and FY04 using existing equipment available to this project task. This additional coring may be needed for obtaining fresh core material (unoxidized sediment) for organic biomarker studies. Processing procedures and sectioning of these additional cores will follow the same protocol as that used in the FY02 coring. Work in FY04 will involve continued analysis of the core samples, especially the time-consuming biomarker work.
Sediment samples will be analyzed for total and organic C, total N, and total S using a Leco elemental analyzer available in USGS organic geochemistry labs (Orem) in Reston, VA. Total P content will be analyzed using a standard geochemical method involving baking at 500° 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 total and organic C, total N, total P, and total S will be calculated using sediment accumulation rates calculated from 210Pb 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 and Florida Bay may provide additional insights into processes and flow patterns.
Planned Outreach: Data and results will be presented at workshops, public forums, and meetings in south Florida. A USGS publication and Fact Sheet are anticipated products for FY03, followed by peer-reviewed journal articles to be produced in FY04. Data and results from this task will contribute to final products for the project, discussed under Task 1. In addition, data from this project will contribute to production of a map of accumulation rates in the Biscayne Bay, Eastern Florida Bay, and Taylor Slough region, which will provide a blueprint of nutrient contamination in this region for management use.