Home Archived October 29, 2018
(i)
USGS Home
SOFIA Home

Linking Land, Air, and Water Management in the Southern Everglades and Coastal Zone to Water Quality and Ecosystem restoration: Task 1, Mercury Cycling, Fate and Bioaccumulation

Metadata also available as - [Questions & Answers] - [Parseable text] - [XML]

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator:
David P. Krabbenhoft

William H. Orem; George R. Aiken

Publication_Date: 1997-2001
Title:
Linking Land, Air, and Water Management in the Southern Everglades and Coastal Zone to Water Quality and Ecosystem restoration: Task 1, Mercury Cycling, Fate and Bioaccumulation
Geospatial_Data_Presentation_Form: project
Online_Linkage:
<https://sofia.usgs.gov/projects/index.php?project_url=int_geochem>
Description:
Abstract:
This proposal identifies work elements that are logical extensions, and which build off, our previous work. Our overall scientific objective is to provide a complete understanding of the external factors (such as atmospheric mercury and sulfate runoff loads) and internal factors (such as hydroperiod maintenance and water chemistry) that result in the formation and bioaccumulation of MeHg in south Florida ecosystems, and to conduct this research is such a way that it will be directly useable by land and water resource managers. More specifically, we will seek to achieve the following subobjectives (1) Extend our mesocosms studies to provide a more omprehensive examination of the newly discovered 'new versus old' mercury effect by conducting studies under differing hydrologic conditions and sub-ecosystem settings so that our experimental results will be more generally applicable to the greater south Florida ecosystem including the STA’s that have been recently constructed and are yielding very high levels of methylmercury but the cause is currently unknown; (2) Seek to further identify the mechanisms that result in extremely high levels of MeHg after natural drying and rewetting cycles in the Everglades and which have major implications for the Restoration Plan; (3) Further our studies on the production of methylmercury in south Florida estuaries and tidal marshes by conducting mass-balance studies of tidal marshes; (4) Begin to partner with wildlife toxicologists funded by the State of Florida to unravel the complexities surrounding methylmercury exposure and effects to higher order wildlife in south Florida; and , (5) Continue to participate with mercury ecosystem modelers who are funded by the State of Florida and the USEPA to evaluate the overall ecological effects of reducing mercury emissions and the risks associated with methylmercury exposure.
Purpose:
Although ecological impacts from phosphorous contamination have become synonymous with water quality in south Florida, especially for Everglades restoration, there are several other contaminants presently entering the Everglades that may be of equal or greater impact, including: pesticides, herbicides, polycyclic aromatic hydrocarbons, and trace metals. This project focuses on mercury, a sparingly soluble trace metal that is principally derived from atmospheric sources and affects the entire south Florida ecosystem. Mercury interacts with another south Florida contaminant, sulfur, that is derived from agricultural runoff, and results in a problem with potentially serious toxicological impacts for all the aquatic food webs (marine and freshwater) in the south Florida ecosystem. The scientific focus of this project is to examine the complex interactions of these contaminants (synergistic and antagonistic), ecosystem responses to variations in contaminant loading (time and space dimensions), and how imminent ecosystem restoration steps may affect existing contaminant pools. The Everglades restoration program is prescribing ecosystem-wide changes to some of the physical, hydrological and chemical components of this ecosystem. However, it remains uncertain what overall effects will occur as these components react to the perturbations (especially the biological and chemical components) and toward what type of 'new ecosystem' the Everglades will evolve. The approaches used by this study have been purposefully chosen to yield results that should be directly useable by land management and restoration decision makers.

Presently, we are addressing several major questions surrounding the mercury research field, and the Everglades Restoration program: (l) What, if any, ecological benefit to the Everglades would be realized if mercury emissions reductions would be enacted, and over what time scales (years or tens of years) would improvements be realized? (2) What is the role of old mercury (previously deposited and residing in soils and sediment) versus new mercury (recent deposition) in fueling the mercury problem? (3) In the present condition, is controlling sulfur or mercury inputs more important for reducing the mercury problem in the Everglades? (4) Does sulfur loading have any additional ecological impacts that have not been realized previously (e.g., toxicity to plant and animals) that may be contributing to an overall decreased ecological health? (5) Commercial fisheries in the Florida Bay are contaminated with mercury, is this mercury derived from Everglades runoff or atmospheric runoff? (6) What is the precise role of carbon (the third member of the 'methylmercury axis of evil', along with sulfur and mercury), and do we have to be concerned with high levels of natural carbon mobilization from agricultural runoff as well? (7) Hundreds of millions of dollars are being, or have been spent, on STA construction to reduce phosphorus loading to the Everglades, however, recently constructed STAs have yielded the highest known concentration of toxic methylmercury; can STA operations be altered to reduce methylmercury production and maintain a high level of phosphorus retention over extended periods of time? The centerpiece of our research continues to be the use of environmental chambers (enclosures or mesocosms), inside which we conduct dosing experiments using sulfate, dissolved organic carbon and mercury isotopic tracers. The goal of the mesocosm experiments is to quantify the in situ ecological response to our chemical dosing, and to also determine the ecosystem recovery time to the doses.

Supplemental_Information:
This project is now part of the combined Linking Land, Air and Water Management in the Southern Everglades and Coastal Zone to Water Quality and Ecosystem Restoration project. It is an extension of the Aquatic Cycling of Mercury in the Everglades (ACME).
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 2001
Ending_Date: 2007
Currentness_Reference: ground condition
Status:
Progress: In Work
Maintenance_and_Update_Frequency: As needed
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -81.331365
East_Bounding_Coordinate: -80.222011
North_Bounding_Coordinate: 25.890877
South_Bounding_Coordinate: 24.67165
Keywords:
Theme:
Theme_Keyword_Thesaurus: none
Theme_Keyword: biogeochemistry
Theme_Keyword: biology
Theme_Keyword: chemistry
Theme_Keyword: hydrology
Theme_Keyword: mercury
Theme_Keyword: mercury cycling
Theme_Keyword: methylmercury
Theme_Keyword: contaminants
Theme_Keyword: bioaccumulation
Theme_Keyword: methylation
Theme_Keyword: ACME
Theme_Keyword: Aquatic Cycling of Mercury in the Everglades
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: environment
Theme_Keyword: inlandWaters
Theme_Keyword: 007
Theme_Keyword: 012
Place:
Place_Keyword_Thesaurus:
Department of Commerce, 1995, Countries, Dependencies, Areas of Special Sovereignty, and Their Principal Administrative Divisions, Federal Information Processing Standard (FIPS) 10-4, Washington, D.C., National Institute of Standards and Technology
Place_Keyword: United States
Place_Keyword: US
Place:
Place_Keyword_Thesaurus:
U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of the United States, and associated areas (Federal Information Processing Standard 5-2): Washington, D. C., NIST
Place_Keyword: Florida
Place_Keyword: FL
Place:
Place_Keyword_Thesaurus:
Department of Commerce, 1990, Counties and Equivalent Entities of the United States, Its Possessions, and Associated Areas, FIPS 6-3, Washington, DC, National Institute of Standards and Technology
Place_Keyword: Broward County
Place_Keyword: Miami-Dade County
Place_Keyword: Palm Beach County
Place:
Place_Keyword_Thesaurus: USGS Geographic Names Information System
Place_Keyword: Big Cypress National Preserve
Place_Keyword: Everglades National Park
Place_Keyword: Florida Bay
Place:
Place_Keyword_Thesaurus: none
Place_Keyword: Central Everglades
Place_Keyword: Greater Lake Okeechobee
Place_Keyword: South East Coast
Place_Keyword: ENR
Place_Keyword: WCA3A
Place_Keyword: STA 2
Access_Constraints: none
Use_Constraints:
These data are subject to change and are not citeable until reviewed and approved for official publication.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David P. Krabbenhoft
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical address
Address: 8505 Research Way
City: Middleton
State_or_Province: WI
Postal_Code: 53562-3581
Country: USA
Contact_Voice_Telephone: 608 821-3843
Contact_Facsimile_Telephone: 608 821-3817
Contact_Electronic_Mail_Address: dpkrabbe@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name: <https://sofia.usgs.gov/publications/ofr/97-454/images/fig1x.gif>
Browse_Graphic_File_Description: map showing location of sampling sites during 1994-1995
Browse_Graphic_File_Type: GIF
Data_Set_Credit:
Project personnel include Mark Olson, John DeWild, Shane Olund, J. Ogreck, and Thomas Sabin. Cindy Gilmour (Academy of Natural Sciences) previously worked on this project.
Native_Data_Set_Environment: html tables
Cross_Reference:
Citation_Information:
Originator:
Haitzer, M.

Aiken, G. R.; Ryan, J. N.

Publication_Date: 2002
Title:
Binding of Mercury (II) to Dissolved Organic Matter: The Role of the Mercury-to-DOM Concentration Ration
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: Environmental Science and Technology
Issue_Identification: v. 36, n. 16, p. 3564-3570
Publication_Information:
Publication_Place: Washington, DC
Publisher: American Chemical Society
Other_Citation_Details:
accessed as of 5/31/2011

The full article is available via journal subscription or single article purchase. The abstract, tables, figures, and bibliography are available at <https://sofia.usgs.gov/publications/papers/hg_dom_binding/>

Online_Linkage: <http://pubs.acs.org/doi/full/10.1021/es025699i>
Online_Linkage: <https://sofia.usgs.gov/publications/papers/hg_dom_binding/>
Cross_Reference:
Citation_Information:
Originator:
Bates, A. L.

Orem, W. H.; Harvey, J.. W.; Spiker, E. C.

Publication_Date: 2001
Title:
Geochemistry of Sulfur in the Florida Everglades: 1994 through 1999
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 01-007
Publication_Information:
Publication_Place: Tallahassee, FL
Publisher: U.S. Geological Survey
Other_Citation_Details: accessed as of 5/31/2011
Online_Linkage: <https://sofia.usgs.gov/publications/ofr/01-007/>
Cross_Reference:
Citation_Information:
Originator:
Bates, Anne L

Orem, William H.; Harvey. Judson W.; Spiker, Elliot C.

Publication_Date: 2002
Title: Tracing sources of sulfur in the Florida Everglades
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: Journal of Environmental Quality
Issue_Identification: v. 31, n. 1, p. 287-299
Publication_Information:
Publication_Place: Madison, WI
Publisher: American Society of Agronomy
Other_Citation_Details: accessed as of 5/31/2011
Online_Linkage:
<https://sofia.usgs.gov/publications/papers/trace_sulfur/JEnvironQual.pdf>
Cross_Reference:
Citation_Information:
Originator:
Simon, N. S.

Cox, T.; Spencer, R.

Publication_Date: 1998
Title:
Data for Periphyton and Water Samples Collected from the South Florida Ecosystem, 1995 and 1996
Geospatial_Data_Presentation_Form: publicaton
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 98-76
Publication_Information:
Publication_Place: Reston VA
Publisher: U.S. Geological Survey
Other_Citation_Details: accessed as of 6/1/2011
Online_Linkage: <https://sofia.usgs.gov/publications/ofr/98-76>
Cross_Reference:
Citation_Information:
Originator:
Gough, L. P.

Kotra, R. K.; Holmes, C. W.; Orem, W. H.; Hageman, P. L.; Briggs, P. H.; Meier, A. L.; Brown, Z. A.

Publication_Date: 2000
Title:
Regional Geochemistry of Metals in Organic-Rich Sediments, Sawgrass, and Surface Water from Taylor Slough, Florida
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 00-327
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Other_Citation_Details: accessed as of 5/31/2011
Online_Linkage: <https://sofia.usgs.gov/publications/ofr/00-327/>
Cross_Reference:
Citation_Information:
Originator:
Krabbenhoft, D. P

Hurley, J. P., Olson, M. L., Cleckner, L. B.

Publication_Date: 1998
Title:
Diel variability of mercury phase and species distributions in the Florida Everglades
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: Biogeochemistry
Issue_Identification: v. 40 no. 2/3, p. 311-325
Publication_Information:
Publication_Place: Dordrecht, Netherlands
Publisher: Kluwer Academic Press
Other_Citation_Details:
accessed as of 6/1/2011

The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website below.

Online_Linkage: <http://www.springerlink.com/content/w35613w6287h4542/>
Cross_Reference:
Citation_Information:
Originator:
Orem, W. H.

Lerch, H. E.; Rawlik, P.

Publication_Date: 1997
Title:
Geochemistry of surface and pore water at USGS coring sites in wetlands of South Florida, 1994 and 1995
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 97-454
Publication_Information:
Publication_Place: Reston, VA
Publisher: U.S. Geological Survey
Other_Citation_Details: accessed as of 5/31/2011
Online_Linkage: <https://sofia.usgs.gov/publications/ofr/97-454>
Cross_Reference:
Citation_Information:
Originator:
Wiener, J. G.

Krabbenhoft, D. P.; Heinz, G. H.; Scheuhammer, A. M.

Publication_Date: 2003
Title: Ecotoxicology of Mercury
Geospatial_Data_Presentation_Form: publication
Publication_Information:
Publication_Place: Boca Raton, FL
Publisher: CRC Press
Other_Citation_Details:
Pages 407-461 in Book of Ecotoxicology, 2nd ed.; 2003; Hoffman, D. J.; Rattner, B. A.; Burton, Jr., G. A.; Cairns, J., editors
Cross_Reference:
Citation_Information:
Originator:
Krabbenhoft, D. P.

Branfireun, B. A.; Heyes, A.

Publication_Date: 2005
Title:
Biogeochemical cycles affecting the speciation, fate, and transport of mercury in the evnironment
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: book
Issue_Identification: v. 34, p. 139-156
Publication_Information:
Publication_Place: Quebec, Canada
Publisher: Mineralogical Association of Canada
Other_Citation_Details:
accessed as of 6/1/2011

Chapter 8 in Mercury: Sources, Measurements, Cycles, and Effects, Michael B. Parsons & Jeanne B. Percival, eds. The table of contents may be viewed on the website below.

Online_Linkage:
<http://www.mineralogicalassociation.ca/index.php?p=25&page=sc34.php>
Cross_Reference:
Citation_Information:
Originator:
Branfireun, B. A.

Krabbenhoft, D. P.; Hintelmann, H.; Hunt, R. J.; Hurley, J. P.; Rudd, J. W. M.

Publication_Date: 2005
Title:
Speciation and transport of newly deposited mercury in a boreal forest wetland: a stable mercury isotope approach
Geospatial_Data_Presentation_Form: publication
Series_Information:
Series_Name: Water Resources Research
Issue_Identification: v. 41
Publication_Information:
Publication_Place: Washington, DC
Publisher: American Geophysical Union
Other_Citation_Details:
accessed as of 6/1/2011

The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website below.

Online_Linkage: <http://www.agu.org/pubs/crossref/2005/2004WR003219.shtml>

Data_Quality_Information:
Logical_Consistency_Report: not available
Completeness_Report: not available
Lineage:
Process_Step:
Process_Description:
In the fall of 1999 we began planning for the design and emplacement of the mesocosums through coordination and collaboration with the SFWMD and FDEP. These activities also included securing permission to use the mesocosums and Hg isotopes in the Water Conservation Areas, Loxahatchee National Wildlife Refuge, and Everglades National Park. We made three field trips in the winter, spring and fall time periods to begin testing of the isotopic method and to collect sediment and water from 10 locations in the Everglades which we transported to Madison, WI to conduct laboratory microcosm tests of the Hg isotope tracing methods. Also, we tested methods for making Hg stem-flow measurements, and made our initial sampling visit to the recently construct STA6 West to make comparative measurements with the original ENR facility.

Began dual sulfur-DOC controlled laboratory experiment to help design field-enclosure scale deployment of these tests. Tests were to be carried out by another investigator in collaboration with Orem, Krabbenhoft, Aiken, Hurley and Gilmour. All of these primary investigators have agreed to make facilities and materials available for these studies, such as Hg isotopes and analysis (Krabbenhoft), methylating bacteria (Gilmour), DOC fractions (Aiken) and laboratory space (Orem). To bring these tests from the laboratory scale the field scale, large quantities of the various DOC fractions will need to be isolated in a trace-metal clean manner to provide enough material for testing. Preliminary work wasplanned for 5/00 and 7/00 in collaboration with Krabbenhoft, Gilmour, and Aiken.

Examined rates of mercury methylation and release of P, N and S from fire events. This followed up on preliminary work conducted in FY 99 on fires in the northern part of WCA 3. We plan to conduct laboratory simulations of fire and rewetting events to examine remobilization of nutrients following fire or extended dry periods when peat oxidation may occur. Field studies of nutrient remobilization following fire or drying events and rewetting were conducted in field enclosures, and in actual burned or dried natural areas as circumstances permited

Examine sulfur concentrations, speciation, and distribution in field-enclosure studies (coordination with mercury field-enclosure studies). The purpose of the field-enclosure work will be to examine how changes in environmental parameters accompanying the restoration effort will affect sulfur geochemistry. Field-enclosure sites were selected to represent various types of environments in the Everglades, such as eutrophic sites, oligotrophic (background) slough/marsh sites, and marl prairies.

Initial installation of small enclosures (USGS) and initial experiments in large (SFWMD enclosures) planned for 5/00, with follow up work in 7/00 and 9/00. Enclosure experiments expected to continue into FY01.

Process_Date: 2000
Process_Step:
Process_Description:
Mesocosm Studies:

We used environmental enclosures placed in the ecosystem (mesocosms) to examine the effects of changing water quality variables on methylmercury production and bioaccumulation. These experiments were designed to examine the effects of individual variables and multivariable interaction effects on methylmercury production. Variables of interest with regard to methylmercury production include: inorganic mercury (added in isotopic form), sulfur, nutrients (especially phosphorus), DOC, and iron.

Our experimental mesocosms had "breathing holes" that were left open to the outside environment during the intervening time between experiments so that the enclosed areas can equilibrate with the native environment. Our observations (direct measurements of pH, dissolved oxygen, temperature, and observations of general visual health) showed that the leaving the mesocosms enclosed for 2-4 months does not produce an artificial "mesocosm effect" and bias our results. During experiments, the breathing holes were closed with silicone stoppers and chemical additions were made to sets of mesocosms to test the effects of the chemical additions on methylmercury production. Each chemical addition (variable) was tested at multiple concentration levels. In some sets of mesocosms, multiple chemical species were added to examine interactive effects. For example, during FY02, mesocosm experiments were conducted at several sites in the Everglades to test the effects of sulfate addition (3 concentration levels), inorganic mercury (3 concentration levels), DOC (2 concentration levels), inorganic mercury plus sulfate (3 concentration levels), and inorganic mercury plus DOC. Following the additions, changes in chemical species (methylmercury and other mercury species, sulfur species, DOC, nutrients, anions, cations, Fe and Mn, redox, conductivity, pH) and microbial activity (sulfate reduction and mercury methylation rates) were determined in surface water, porewater, and sediments in the mesocosms over time (usually followed for several months following the start of the experiment). In addition, during each experiment we established at least two control mesocosms to check for enclosure effects, and we took samples from the native environment near the mesocosms to assure that the mesocosms were tracking the overall season changes that are observed annually in the ecosystem.

We also proposed to follow-up on our previous mesocosm studies on methylmercury production. Experiments will be repeated in order to verify and expand on results from FY02. A new feature in FY03 will be the use of isotopically labeled sulfate in the chemical additions to follow changes in sulfur geochemistry and its effects on methylmercury production. Our previous mesocosm experiments were focused in the northern Everglades. In FY03 we propose to add another mesocosm site in an STA (probably STA-2). These constructed wetlands can behave as zones of low methymercury production (such as ENR), but also can produce very high levels of methylmercury (STA-2). The reasons for this are not fully understood, and mesocosm experiments in the STA’s will be designed to provide managers with information on how best to operate the STA’s to minimize methylmercury production.

Process_Date: 2003
Process_Step:
Process_Description:
Drought/Burn and Rewet Experiments:

Phase I ACME showed a very dramatic (about a 10-100X increase) effect of drying and rewetting cycles on methylmercury production bioaccumulation in fish in the Everglades. In FY02, we initiated a laboratory experiment to see if we could reproduce the drying and rewetting effect on mercury methylation in Everglades peat, and to provide more mechanistic information on the geochemical mechanisms. That experiment is currently ongoing and is expected to be completed by the end of FY02. It is likely follow-up experiments will be needed, given that we only used peat samples from one site, and the complexity of this phenomenon will likely need further evaluation.

The experimental approach involved: (1) collection of a series of small cores and transport to a controlled clean laboratory environment in Reston, Virginia, or St. Leonard, Maryland, (2) allowing the cores to dry completely for varying lengths of time under controlled conditions, (3) rewetting the cores with water collected from the original field sites, and is some cases spiked with stable mercury isotopes, and (4) analysis of surface water, porewater, and sediments in the rewetted cores at intervals of time following rewetting. Analytes measured in the samples included methylmercury and other mercury species, sulfur species, nutrients, anions, cations, DOC, and sediment parameters (organic carbon, total N, total P, total S, S species). Biological parameters measured included methylmercury production and sulfate reduction rates. The initial experiment was begun in March 2002 and scheduled to end in September 2002.

A follow-up experiment will be conducted in FY03 (continuing into FY04) using a larger core approach and additional sites (a high sulfur and low sulfur site in the northern Everglades). The larger cores will slow down the drying process in the lab, more closely simulate conditions in the ecosystem, and allow for larger sample sizes to ease the analysis step. Additional changes to the follow-up experiment will include shorter dry times and extended sampling times following rewet.

Process_Date: 2004
Process_Step:
Process_Description:
Florida Bay Mercury Methylation and Sulfur Biogeochemistry:

In FY02 we collaborated with Darren Rumbold (SFWMD) and David Evans (NOAA) to execute a preliminary examination of mercury methylation rates in Florida Bay. The extremely scant literature currently available on mercury methylation in marine sediments (one published paper) suggested very low or now methylation) had persuaded us not to prioritize the Florida Bay ecosystem previously. However, our initial evaluations indicate that in fact moderate to high levels of methylation can occur in Florida Bay sediments, and may represent a primary source of methylmercury to commercial and sport fisheries. These results are were quite surprising, giving the very high levels of sulfide (100 ppm and higher) that are known to exist in Florida Bay sediments generally, and the previously identified inhibition effect of sulfide on mercury methylation. The objective of this task will be to determine a spatially complete assay of mercury methylation rates in Florida Bay, and to ascertain how the process proceeds in such sulfidic and carbon-poor sediments.

Krabbenhoft/Orem/Aiken will conduct a synoptic sampling of Florida Bay sub-ecosystems (mud flats, embayments, tidally influenced streams, etc…) to examine the biogeochemistry of mercury methylation in Florida Bay sediments. These investigations will include a complete examination of the biogeochemistry of sulfur, dissolved organic carbon, and mercury speciation and methylation rates in Florida sediments and porewater. Sediment and porewater samples will be taken and analyzed for sulfur speciation and concentrations in sediments and sediment porewater. The same overall procedures used in the Everglades marshes will be employed in Florida Bay (with some modifications to account for the oozing sediments present there), which will allow for direct comparison of our results between these contrasting but effacing ecosystems.

Preliminary efforts done in collaboration with Rumbold and Evans in Florida Bay during FY02 will greatly aid our site selection process and interpretation. Sites will be chosen to represent the majority of the east-to-west transitioning environments present in Florida Bay, as well and the near versus off shore variations. Sampling would be conducted in collaboration with Orem and Aiken.

Process_Date: 2004
Process_Step:
Process_Description:
Collaborations with the TIME and SICS projects:

The Placed Based Studies program has supported the development of two major hydrologic investigations and model developments in south Florida: TIME and SICS. These efforts have lead to a greatly improved understanding of the hydrologic transport processes (spatially and temporally) within Everglades National Park and the Water Conservation Areas. However, the investigators of these projects have not explicitly interfaced with biogeochemical investigations to extend the use of these hydrologic models or the power of marrying the geochemistry databases to the water flow information to yield mass flux rates. These types of calculations are important because the Everglades are a dynamic ecosystem and current modeling exercises to predict the future Everglades have primarily focused on static water level estimates, and have not considered dynamic properties like water and constituent mass fluxes. During FY03, we will initiate collaborations with the lead investigators of these two projects (Schffranek and Swain) to combine the strengths of the biogeochemistry and hydrologic research efforts to develop mass fluxes of nutrients, sulfur and mercury for the marshes.

Lead investigators (Krabbenhoft, Orem and Aiken) will first conduct exploratory conversations with the TIME and SICS research teams to develop a strategy for marrying the two research efforts more closely. From these discussions, we will identify any data gaps that may currently exist between these studies (e.g., diffusion rate estimates) and formalize field plans to acquire the needed information. Members from each research team will participate in assembling the necessary databases to derive the mass flux estimates.

This effort will be initiated in FY03, but will probably require additional follow up in FY04. Many of the ecosystem types where the TIME and SICS researchers are most active in Everglades National Park and near the coastal margins have not been evaluated at all by the ACME team. Therefore, some initial sampling of these environments will be necessary to support the completion of this sub task. Sampling efforts will be focused on those areas or specific locations where the TIME and SICS teams have monitoring instillations, which should expedite the mass flux calculations.

Process_Date: 2004
Process_Step:
Process_Description:
Mercury Cycling and Bioaccumulation in Big Cypress National Preserve:

The ACME Phase I researchers necessarily had to focus their intensive, process oriented research in fewer locations due to the extremely time intensive nature of this work. Because of this, many sub ecosystem types have remained largely uninvestigated with respect to mercury contamination and bioaccumulation. One notable example is Big Cypress National Preserve, where Orem and McPherson have recently showed the existence of unnaturally high levels of nutrients and sulfate (compared to southern WCA 3 and Shark River Slough). In other sub ecosystems where the ACME team has worked, slight to modest levels of nutrient and sulfate contamination have generally co-existed with the highest levels of methylmercury, such as central WCA-3A.

Synoptic sampling efforts will be initiated in the fall/winter of FY03 to identify whether high levels of methylmercury exist in Big Cypress Preserve, and whether there are any spatial trends similar to what has been observed in other locations of the Everglades. Surface water, porewater, sediment and biological (e.g., periphyton, Gambusia, etc.) samples will be collected from sites throughout the Big Cypress Preserve. Although much of Big Cypress is a sandy soil, there are areas where peat or peaty muck is present and shallow cores and porewater can be obtained. Samples will be analyzed for total mercury, gaseous elemental mercury, and methylmercury species. Sampling efforts will be conducted in concert with Orem and Aiken to derive a complete geochemical data set to evaluate the similarities and/or differences between Big Cypress Preserve and the Conservation Areas. In the summer of FY03, a sampling trip will be conducted to make process specific measurements of methylation, demethylation, photo reduction, and gaseous mercury evasion.

Work in FY03 will focus on sampling at selected sites throughout the Preserve, and chemical analysis of the samples. The study area will extend from the agricultural region north of the Big Cypress Preserve to the Ten Thousand Islands Area in the south. Sites will be primarily accessed by ground vehicle, but we will also explore possible helicopter support from the Big Cypress National Preserve for accessing more remote sites. Results from FY03 will be compiled and prepared for publication in FY04. The study will be the first to explore mercury speciation, cycling and bioaccumulation in Big Cypress Preserve, and to assess if sulfur and methylmercury production is an issue of concern. Results will assist managers in assessing potential threats to the Big Cypress Preserve and the Ten Thousand Islands Area from nutrient and sulfur inputs.

Process_Date: Unknown
Process_Step:
Process_Description:
Work planned for FY 2004 includes:

1. Mesocosm Studies The proposed 2003 mesocosm experiments will be conducted at the 3A-15 site in the central Everglades, that provided the highest MeHg response in the 2002 experiments, and also provides an ideal location for the DOC and sulfate addition experiments, and for the sulfur toxicity experiments described later. In total, we will have over 60 mesocosm at site 3A15 involved in our research, and in essence each mesocosm is the equivalent of a sampling site. MeHg mesocosm experiments will be conducted between mid June and the end of October 2003. Conducting the experiment during this wet season/summer period should produce the maximum MeHg production signal, due to overall higher microbial activity in summer months. Mesocosms used in the experiment will either be newly purchased or previously used mesocosms that have never had mercury isotopes added (such as controls, sulfate only, or DOC only additions). All previously used mesocosms will be relocated at the 3A-15 site for this experiment. Installation of the new mesocosms and relocation of existing mesocosms (some moved from other sites in the Everglades) took place during mid-April 2003 to allow time for reequilibration of the sediment and water prior to initiating the experiment in June. After installation, mesocosms are left open (six two-inch breather holes drilled on the perimeter of each mesocosm) to its surroundings, which allows for free exchange of water. At the start of experiments, the holes are plugged with silicone stoppers to isolate the interior environment of the mesocosm from the surroundings and maintain the presence inside the mesocosm of the chemical.

Ten mesocosms will be used for sulfate plus mercury additions. The ten mesocosms will be grouped in sets of two for addition of sulfate at five different dosing (i.e. concentration) levels and a single mercury level of 1X ambient atmospheric (22 ug/m2; or 14.3 ug Hg). Experiments performed in 2000-2002 have adequately defined the mercury-only addition response over a range of 0 to 2X ambient dosing level. The sulfate dosing levels are 4, 8, 12, 16, and 20 mg/l, based on the results of our 2002 mesocosms. The sulfate is added to the mesocosms as sodium sulfate dissolved in site water. The appropriate amount to be added to each mesocosm to reach the target concentration is calculated based on the volume of water in each mesocosm. Each dosing level has a duplicate mesocosm for quantifying natural variability in the response, which is epically high for sediment-based measurements (e.g., net methylation rates). A group of 6 mesocosms (three sets of duplicates for each dosing level) will be used to examine the effects of DOC and mercury isotope dosing at 3 different dosing levels. DOC isolated from eutrophied sites near canal discharge in Water Conservation Area 2A will be used for the experimental dosing. Target addition levels for DOC will be about 30, 40 and 50 mg/l. The DOC is added to the mesocosms as a concentrated solution and mixed by gentle stirring of the surface water. Finally, a group of two mesocosms will have DOC, sulfate, and mercury isotope added. These mesocosms are intended to evaluate the synergistic effects of sulfate, DOC, and mercury on MeHg production. The dosing level to be used in this mesocosm pair will likely be about 14.3 ug Hg, 12 mg/l sulfate and 40 mg/l DOC. As with our previous mesocosm experiments, we will employ control mesocosms to monitor the natural variability in the system and to evaluate whether there are any unnatural 'mesocosm' effects. To establish natural variability and to control for mesocosm effects, two mesocosms will be set aside as controls, and in addition two sites will be established in the marsh near the control mesocosms as ambient controls. The mesocosm controls will be plugged with silicone stoppers and treated in a fashion similar to the experimental mesocosms, but no dosing of any kind will be added. The experiment will commence on June 23, 2003. Samples of surface water, porewater, Gambusia and sediments will be collected at the mesocosm and outside controls to define the initial conditions of the site. After sampling, all mesocosms will be plugged, and appropriate chemical doses will be added. Follow-up sampling of the experimental mesocosms, mesocosm controls, and outside controls for surface water, porewater, Gambusia, and sediments will continue on days 1, 61, and 119. In addition, we will conduct a diel sampling study of a least 4 mesocosms (a control, g+sulfate, Hg+DOC, and Hg+sulfate+DOC) in which scientists remain on site for approximately 30-36 hours and sampling each mesocosm approximately every three hours. After the initial doses, subsequent sulfate dosing is scheduled for days 14, 28, 42, 63, 78, 91, and 105. Mercury-clean procedures are followed for all sampling, which provides minimal contamination acceptable for all analytes. Sediments are collected using a small push core to minimize disturbance of the mesocosm interior. Analytes measured in surface water, suspended particulates and porewater include: total mercury and MeHg (ambient pools and isotope spikes), anions, cations, sulfur species (sulfate, thiosulfate, sulfite, sulfide), nutrients (nitrate, ammonium, and phosphate), DOC, iron and manganese, redox, dissolved oxygen, and pH. Sediment geochemical analyses include: total mercury and methylmercury (ambient pools and isotope spikes), total sulfur, sulfur species (AVS, sulfate, disulfides, and organic sulfur), total and organic carbon, total nitrogen, total phosphorus, and metals. Sediments are also measured for various microbial parameters, including mercury methylation rate, and sulfate reduction rates. Time-sensitive parameters are measured in motel-room laboratories within hours of sample collection. Samples for later analyses are stored in an appropriate fashion (frozen, cool, etc.) and shipped back to laboratory facilities at the various PI’s labs (Middleton, WI; St. Leonard, MD; Reston, VA; Boulder, CO). At the termination of the experiment (currently scheduled for October 14, 2003), the silicone stopper plugs are removed from the mesocosms, and all equipment is removed from the site, with the exception of mesocosms which are left in place for potential future studies.

(2) Developing a predictive model for methylation and sulfur cycling

Methodology - Our studies suggest that there are three main, manageable, controls on MeHg production in the STAs: antecedent soil chemistry, inflowing water chemistry, and interior water level maintenance. Since MeHg production is substantially dependant on the amount and type of sulfur present in soils, and on the mercury content of soils agricultural and non-agricultural soils may have very different sulfur and mercury levels because of land-use history, although to our knowledge little information is available on soil sulfur and mercury chemistry in the STAs except for research sites in ENR and STA 2 Cell 1. Inflowing water contains three critical constituents that strongly relate to methylmercury formation, transport and bioaccumulation: sulfate, organic carbon and Hg. In addition, these constituents may change the character of soils in the long run. Last, the timing and duration of flow-through of water of the STAs (i.e., (hydroperiod) can dramatically affect MeHg production through the initiation of drying/rewetting cycles that have been shown to dramatically increase MeHg in Everglades soil. We propose a set of studies conducted over two years that are designed to produce a predictive model for MeHg production in the STAs. The study will be carried out via agreements with USGS researchers and with the Academy of Natural Sciences Environmental Research Center (ANSERC) in St. Leonard, Maryland. The objective of this study is to develop a predictive capability based on soil geochemistry, quality of inflowing water, and hydrologic conditions. Although this research arises from the need to manage existing STAS, it will also be useful in site selection for any future treatment areas and for planning and operation of future water reservoirs. The proposed study has several linked components: (1) Survey of soil geochemistry, Hg and MeHg in STA soils; (2) Follow up examination of soil geochemistry, Hg and MeHg at ACME Everglades sites; (3) Examination of the influence of drying and wetting cycles across a wider range of soil types.

STA soil geochemistry - The Survey of soil geochemistry in STA’s is an examination of STA soil geochemistry, especially sulfur, iron, and Hg/MeHg content. This component consists primarily of a field survey of soil geochemistry across the STAs. The objective of this survey is to test our Everglades-based understanding of MeHg production in the STAs. The primary drivers of MeHg within Everglades surface soils are sulfur, Hg, organic carbon and hydrologic conditions. A survey of soil conditions within the STAs will allow us to determine if the same drivers operate in STA soils, with their different land-use and hydrologic-maintenance histories. Currently operating STAs would be examined first in summer/fall 2003, then the survey would be expanded to STAs under construction and planned for construction in spring 2004. Site-selection criteria would include examination of a wide variety of soil and land-use types, and the management needs of the agencies responsible for Everglades restoration planning and operation. Specific objectives of this component are to provide baseline data for geochemistry and Hg/MeHg content of STA soils, and to evaluate the ACME conceptual model for control of MeHg production in Everglades soils for STA soils. Six sites within the STAs will be examined in fall 2003 and six more in 2004. Site access will be via helicopter. Mercury and MeHg will be measured in surface soils, interstitial waters, surface waters, periphyton and gambusia. Other standard ACME analytes to be measured include for bulk sediment: total sulfur, acid volatile sulfide, chromium reducible sulfur, organic sulfur, organic carbon, bulk density, and moisture content. Surface waters and porewaters will be analyzed for sulfate, partially reduced sulfate species, sulfide, total iron, total manganese, and dissolved organic carbon using the previously referenced methods.

Soil biogeochemistry at ACME Everglades sites - The ACME project examined eight discrete Everglades sites (ENR 103, F1, U3, 2BS, 3A15, 3A33, TS7, and TS9) in detail, 2-3 times per year from 1995 through 1998, and that covered most of the north-to-south extent of the ecosystem. These data have been used to generate a general conceptual model for control of MeHg reduction in the Everglades. There are a number of reasons to look at the sites again in 2003. First, decreases in MeHg in fish and wading birds have been observed in many areas of the central Everglades during that time period, but there is no information on any changes in MeHg in soils and water from the ACME sites. Second, additional data density, especially during a different hydrologic period, will provide a more robust data set for comparison with STA soils, and diagenetic modeling. Last, there are some additional parameters that are needed for the diagenetic model that were not collected during 1995-1998, particularly solid-phase Fe speciation, which is needed to model microbial Fe reduction. Periodic resampling of the ACME sites is relatively inexpensive, and will provide valuable long-term data on changes in Hg cycling in the Everglades ecosystem. Sampling conducted at site ENR103 will provide valuable insights into STA biogeochemistry after several years of operation, particularly how long-term sulfate loading has impacted geochemistry and MeHg production in this soil. ENR soils were agricultural prior to conversion, and the high S content of these soils has minimized MeHg production at this site since start-up. Specific objectives of this component are: (1) measure Hg/MeHg concentrations in soils, soil interstitial waters, surface waters and gambusia at the eight main ACME sties; (2) examine potential changes in MeHg concentrations at ACME sites, in comparison with declines in MeHg in wading bird and largemouth bass in the central Everglades; (3) examine changes in soil geochemistry and MeHg in response to changing flow patterns and sulfate loading, particularly in 2BS where substantially increased sulfate loading has occurred since 2000; and, (4) collect information on iron cycling that is needed for construction of the diagenetic MeHg model.

Six to eight ACME sites in the Everglades will be revisited in June or July of 2003. Sites will include ENR103, F1, U3, 2BS, 3A33, 3A15, TS7 and TS9. Site access will be via helicopter. Mercury and MeHg will be measured in surface soils, interstitial waters, surface waters, periphyton and gambusia. Other standard ACME analytes to be measured include for bulk sediment: total sulfur, acid volatile sulfide, chromium reducible sulfur, organic sulfur, organic carbon, bulk density, and moisture content. Surface waters and porewaters will be analyzed for sulfate, partially reduced sulfate species, sulfide, total iron, total manganese, and dissolved organic carbon using the previously referenced methods.

(3) Sulfur Biogeochemistry and Toxicity Experiments

Our hypothesis is that high sulfide levels have played an important, yet previously unrecognized role in the proliferation of cattail in heavily S and P contaminated areas of the Everglades. To test this hypothesis, we propose to employ mesocosms and sulfate dosing in sawgrass and cattail dominated sites of WCA3A. The sites will be in relatively close proximity to each other, probably near tree islands where cattails are often found. Mesocosms would be installed at these sites and allowed to equilibrate for a period of couple months. As with the other mesocosms (described above), holes in the sides of the mesocosms would allow exchange of water with the outside during this equilibration period. The experiment would involve addition of sulfate at three levels: 100 mg/l, 50 mg/l, and 20 mg/l; each level run in triplicate. A pair of control mesocosms would also be run at each site (no sulfate addition). A pair of external control sites (no mesocosm, monitoring of external environment) would also be employed at each location (cattail and sawgrass). Sulfate added to each mesocosm would be calculated based on the volume of water at the time of the experiment, and the amount needed to bring the mesocosms up to the desired concentrations. Sulfate additions would initially be conducted biweekly, and sulfate concentrations monitored to determine future addition needs. Surface water in each mesocosm and in controls (mesocosm and external controls) would be routinely collected (biweekly to monthly) and analyzed for anions, cations, and nutrients. More intensive sampling of surface water, and porewater, and biological sampling would be conducted at least 4 times per year during the initial period of the experiment. Surface and porewater will be analyzed for sulfur species, anions, cations, and nutrients. Biological studies to be conducted would include rates of respiration and photosynthesis in macrophytes, abundance and types of periphyton on submerged periphytometers, and numbers and types of macroinvertebrates. We anticipate that the toxicological effects to plants may require many months to be detectable, and therefore we are planning for this experiment to run for two years. At the end of the study, intensive surface water, porewater, sediment, and biological analyses will be conducted. Coring and removal of plants from the mesocosms for further study will be conducted at this time.

(4) Mass Balance Studies of Methylmercury in Tidal Marshes of Shark River Slough The goal of this work element is to collaborate with coastal zone researchers in the USGS (Eduardo Patino) to make use of the ongoing data gathering, sampling and instrumentation to determine if tides do serve to "pump" methylmercury from coastal environments to the oceans. To initiate this research, we will conduct a sampling effort at an instrumented (gauge height, flow rate and direction, pH, salinity, DO, and temperature) over an entire tidal cycle during the summer and winter periods to construct mass flux estimates for tidal creeks in Shark River Slough. Samples will be taken at hourly intervals over the 8-12 hour tidal cycle. Samples will include surface water, suspended particulates, and porewater, which will be analyzed for total mercury, methylmercury, sulfate, sulfide, DOC, chloride, and major cations.

Process_Date: Unknown
Process_Step:
Process_Description:
For this task in FY05, we plan to execute six interrelated but independent efforts (1) to conclude the sulfate, DOC and Hg dosing studies initiated previously by executing a final sampling of the mesocosms in the Fall of 2004; (2) to examine potential mitigating (methylation abatement) procedures that may be implemented in critical or particularly sensitive parts of the ecosystem (e.g., iron and selenium additions to the intact mesocosms) (3) to support the Sulfur Toxicity mesocosm study by conducting a mercury/methylmercury sampling in those mesocosms in the spring/summer of 2005; (4) to extend our examinations of the potential for exacerbated methylmercury production in Big Cypress National Preserve by conducting a synoptic sampling effort in the spring/summer 2005, and initiating mesocosm tests there; (5) to conduct a limited survey of other coastal marsh settings (about 2-4 sites on differing coastal settings in south Florida) to extend the observations initiated in FY04; and, (6) to conduct a limited synoptic survey of the Everglades in locations we suspect the methylmercury hotspot may have migrated. Brief details of each follow:

1. Starting in 2001, we initiated the use of mesocosms to provide constituent-specific quantitative estimates of the relative effects of mercury, sulfate and DOC loading on the methylation process in the Everglades. These experiments have lead to many novel and paradigm forming observations that had never been even proposed by the scientific community, including the old vs. new mercury discovery. In the more recent experiments, we discovered that the old paradigm of DOC inhibiting mercury availability to methylation was not only wrong, the opposite was actually true! What we observed was that not only did DOC additions make new mercury more available for methylating microbes, but that old mercury (previously buried in sediments) is also activated by DOC loading. These findings are especially important given the parallel discovery that much of the DOC present down-stream of the EAA canal discharges is due to mobilization of humic acids from the drained soils there.

2. Although our mesocosm tests to date have focused on the factors known to exacerbate (or speed) methylation in the environment, these test chambers can be equally well adapted for testing whether there may be solutions to the problem. Mercury methylation is almost entirely regulated by microbial processes, and as such competing processes, or those that limit mercury uptake, are certainly possible. Recent literature on test-tube scale incubations under laboratory conditions suggest that selenium and iron [Fe(III)] additions may prove useful in some situations for limiting methylmercury production. Such a strategy may prove useful in a setting like the STAs, where downstream transport of de novo produced methylmercury is a concern ecologically, and for permit renewal. It is interesting to note that one common feature of the STAs that yield little or no excess methylmercury is that excess iron that is also present. For this part of Task 2 we will conduct a limited number of trial Fe(III) and selenium (added as sodium selenite). For selenium, hypothesize that an important mechanism diminishing the availability of mercury to aquatic food webs occurs through complex interactions between insoluble mercury selenides that may result in long-term retirement of mercury from actively cycling (and bioaccumulating) pools in the environment. We will investigate this hypothesis through study of the effects of graduated additions of small amounts of selenium to mercury-contaminated aquatic ecosystems and determine the impact of this supplemental selenium on accumulation of mercury at different trophic levels of indigenous food webs

3. Sulfur Toxicity Experiment Mercury Sampling - This experiment will continue in FY05, with major sampling efforts in November 2004, and March and August 2005. The experiment tests the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a toxicological impact on native macrophytes in the ecosystem by resulting in high levels of sulfide in porewaters of affected areas. Sulfide toxicity has been shown in several environments to negatively impact freshwater aquatic plants. This experiment will test the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a significant effect on macrophytes in the ecosystem. ACME researchers have concluded that excessively high sulfide levels also limit inorganic mercury bioavailability, and thus reduced levels of methylmercury are coincident with sulfidic zones. Sampling conducted annually (spring summer 05) in these mesocosms will help to confirm or refute this hypothesis.

4. Methylation Controls in BCNP - Results from a preliminary water quality survey in BCNP conducted in FY03 and FY04 indicate that some areas of BCNP have higher than anticipated methylmercury (MeHg) concentrations. While most of the Preserve has very low levels of sulfate, much higher concentrations are found in canals outside the Preserve, especially the L28. Restoration plans call for diverting water from the L28 into BCNP to increase water levels. However, the resulting increased sulfate load entering the Preserve in this canal water may have the unwanted effect of stimulating MeHg production and bioaccumulation here. To test this hypothesis we propose to conduct limited mesocosm studies of MeHg production in response to increased sulfate loads in BCNP, similar to studies we have already conducted in the central Everglades. Results from these tests will provide managers with information on the effects of diverting water of high sulfate concentrations into BCNP, so that costs and benefits of this planned diversion can be assessed, and also provide possible confirmatory results for our other mesocosm studies.

5. MeHg Production in the Coastal Zone - As mentioned above, there is a major disconnect between past work on mercury cycling (freshwater emphasis) and human exposure to methylmercury (primarily from consumption of marine fish). Work in FY05 will begin studies of the mechanism by which MeHg is produced in the coastal zone of the greater Everglades. This task will specifically focus on the occurrence and distribution of mercury and methylmercury in coastal marshes (water, sediment and lower trophic levels), as well as a few key process measurements (methylation and demethylation). FY05 efforts will focus on field surveys, similar to our approach in the freshwater Everglades, which will be followed by experimental work in subsequent years. Investigations aimed at understanding MeHg production and bioaccumulation in the coastal marine environment has been identified as a principal objective of future Hg research at a recent USGS mercury Workshop for DOI scientists and land managers.

6. Methylmercury hotspot survey - Overall levels of methylmercury in the central Everglades have been decreasing for several years, but until recently it was difficult to ascertain the controlling reason(s). Our mesocosm tests confirmed that mercury, sulfate, and DOC declines could be responsible, but all were suspected to have changed over the past 4-5 years due to Decompartmentalization and Sheetflow Enhancement. Recently, the State of Florida's DEP conducted a TMDL study and concluded that regulations emplaced in 1989 to reduce mercury emissions were the driving force. However, upon careful examination of ACME data, we found striking evidence to suggest that dramatic (>95%) declines in sulfate levels in the central Everglades were the more likely cause. If this is the case, this observation has profound implications for the overall benefit from reduced sulfate loads, and scientifically challenges the long held belief that the Everglades have always had a mercury problem. In order to test our conclusion, we propose to conduct a systematic survey of sites across the Everglades (some traditional ACME sampling sites and some new) in order to determine whether the sulfate plume has moved, and the corresponding methylmercury hotspot.

1. Starting in 2001, we initiated the use of mesocosms to provide constituent-specific quantitative estimates of the relative effects of mercury, sulfate and DOC loading on the methylation process in the Everglades. These experiments have lead to many novel and paradigm forming observations that had never been even proposed by the scientific community, including the old vs. new mercury discovery. In the more recent experiments, we discovered that the old paradigm of DOC inhibiting mercury availability to methylation was not only wrong, the opposite was actually true! What we observed was that not only did DOC additions make new mercury more available for methylating microbes, but that old mercury (previously buried in sediments) is also activated by DOC loading. These findings are especially important given the parallel discovery that much of the DOC present down-stream of the EAA canal discharges is due to mobilization of humic acids from the drained soils there.

2. Although our mesocosm tests to date have focused on the factors known to exacerbate (or speed) methylation in the environment, these test chambers can be equally well adapted for testing whether there may be solutions to the problem. Mercury methylation is almost entirely regulated by microbial processes, and as such competing processes, or those that limit mercury uptake, are certainly possible. Recent literature on test-tube scale incubations under laboratory conditions suggest that selenium and iron [Fe(III)] additions may prove useful in some situations for limiting methylmercury production. Such a strategy may prove useful in a setting like the STAs, where downstream transport of de novo produced methylmercury is a concern ecologically, and for permit renewal. It is interesting to note that one common feature of the STAs that yield little or no excess methylmercury is that excess iron that is also present. For this part of Task 2 we will conduct a limited number of trial Fe(III) and selenium (added as sodium selenite). For selenium, hypothesize that an important mechanism diminishing the availability of mercury to aquatic food webs occurs through complex interactions between insoluble mercury selenides that may result in long-term retirement of mercury from actively cycling (and bioaccumulating) pools in the environment. We will investigate this hypothesis through study of the effects of graduated additions of small amounts of selenium to mercury-contaminated aquatic ecosystems and determine the impact of this supplemental selenium on accumulation of mercury at different trophic levels of indigenous food webs

3. Sulfur Toxicity Experiment Mercury Sampling - This experiment will continue in FY05, with major sampling efforts in November 2004, and March and August 2005. The experiment tests the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a toxicological impact on native macrophytes in the ecosystem by resulting in high levels of sulfide in porewaters of affected areas. Sulfide toxicity has been shown in several environments to negatively impact freshwater aquatic plants. This experiment will test the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a significant effect on macrophytes in the ecosystem. ACME researchers have concluded that excessively high sulfide levels also limit inorganic mercury bioavailability, and thus reduced levels of methylmercury are coincident with sulfidic zones. Sampling conducted annually (spring summer 05) in these mesocosms will help to confirm or refute this hypothesis.

4. Methylation Controls in BCNP - Results from a preliminary water quality survey in BCNP conducted in FY03 and FY04 indicate that some areas of BCNP have higher than anticipated methylmercury (MeHg) concentrations. While most of the Preserve has very low levels of sulfate, much higher concentrations are found in canals outside the Preserve, especially the L28. Restoration plans call for diverting water from the L28 into BCNP to increase water levels. However, the resulting increased sulfate load entering the Preserve in this canal water may have the unwanted effect of stimulating MeHg production and bioaccumulation here. To test this hypothesis we propose to conduct limited mesocsom studies of MeHg production in response to increased sulfate loads in BCNP, similar to studies we have already conducted in the central Everglades. Results from these tests will provide managers with information on the effects of diverting water of high sulfate concentrations into BCNP, so that costs and benefits of this planned diversion can be assessed, and also provide possible confirmatory results for our other mesocosm studies.

5. MeHg Production in the Coastal Zone - As mentioned above, there is a major disconnect between past work on mercury cycling (freshwater emphasis) and human exposure to methylmercury (primarily from consumption of marine fish). Work in FY05 will begin studies of the mechanism by which MeHg is produced in the coastal zone of the greater Everglades. This task will specifically focus on the occurrence and distribution of mercury and methylmercury in coastal marshes (water, sediment and lower trophic levels), as well as a few key process measurements (methylation and demethylation). FY05 efforts will focus on field surveys, similar to our approach in the freshwater Everglades, which will be followed by experimental work in subsequent years. Investigations aimed at understanding MeHg production and bioaccumulation in the coastal marine environment has been identified as a principal objective of future Hg research at a recent USGS mercury Workshop for DOI scientists and land managers.

6. Methylmercury hotspot survey - Overall levels of methylmercury in the central Everglades have been decreasing for several years, but until recently it was difficult to ascertain the controlling reason(s). Our mesocosm tests confirmed that mercury, sulfate, and DOC declines could be responsible, but all were suspected to have changed over the past 4-5 years due to Decompartmentalization and Sheetflow Enhancement. Recently, the State of Florida's DEP conducted a TMDL study and concluded that regulations emplaced in 1989 to reduce mercury emissions were the driving force. However, upon careful examination of ACME data, we found striking evidence to suggest that dramatic (>95%) declines in sulfate levels in the central Everglades were the more likely cause. If this is the case, this observation has profound implications for the overall benefit from reduced sulfate loads, and scientifically challenges the long held belief that the Everglades have always had a mercury problem. In order to test our conclusion, we propose to conduct a systematic survey of sites across the Everglades (some traditional ACME sampling sites and some new) in order to determine whether the sulfate plume has moved, and the corresponding methylmercury hotspot.

Process_Date: Unknown
Process_Step:
Process_Description:
For this task in FY06, we plan to execute four interrelated but independent efforts (1) Continued monitoring of the Sulfur Toxicity Mesocosms; (2) complete the initial examination of the iron and selenium dosing mesocosms; (3) participate in the Big Cypress National Preserve synoptic surveys; and (4) to repeat sampling along the coastal mangroves of the Shark River slough system. Brief details of each follow:

(1) Sulfur Toxicity Experiment Mercury Sampling - This experiment will continue in FY06, with major sampling efforts in November 2004, and March and August 2006. This experiment tests the hypothesis that excess sulfate entering the Everglades from agricultural runoff results in the generation of high sulfide levels porewaters of affected areas, which by itself can exhibit toxicity, but also many secondary deleterious effects (e.g., suffocation, limitation of nutrient uptake). Sulfide toxicity has been shown in several environments to negatively impact freshwater aquatic plants. This experiment will test the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a significant effect on many native macrophytes in the ecosystem, but that cattail is largely robust to sulfide toxicity. Although the primary emphasis on this experiment is to evaluate the possible toxicity of sulfide on native Everglades vegetation, the opportunity to study the sulfur loading effects on Hg methylation and bioaccumulation is obvious. Sampling conducted in the mesocosms will help to confirm or refute this hypothesis.

(2) Although our mesocosm tests to date have focused on the factors known to exacerbate (or speed) methylation in the environment, these test chambers can be equally well adapted for testing whether there may be solutions to the problem. Mercury methylation is almost entirely regulated by microbial processes, and as such competing processes, or those that limit mercury uptake, are certainly possible. Recent literature on test-tube scale incubations under laboratory conditions suggest that selenium and iron [Fe(III)] additions may prove useful in some situations for limiting methylmercury production. Such a strategy may prove useful in a setting like the STAs, where downstream transport of de novo produced methylmercury is a concern ecologically, and for permit renewal. It is interesting to note that one common feature of the STAs that yield little or no excess methylmercury is that excess iron that is also present. For this part of the task we will conduct a limited number of trial Fe(III) and selenium (added as sodium selenite). For selenium, hypothesize that an important mechanism diminishing the availability of mercury to aquatic food webs occurs through complex interactions between insoluble mercury selenides that may result in long-term retirement of mercury from actively cycling (and bioaccumulating) pools in the environment. We will investigate this hypothesis through study of the effects of graduated additions of small amounts of selenium to mercury-contaminated aquatic ecosystems and determine the impact of this supplemental selenium on accumulation of mercury at different trophic levels of indigenous food webs

(3) Methylation Controls in BCNP - Results from a preliminary water quality survey in BCNP conducted in FY04 and FY05 indicate that some areas of BCNP have higher than anticipated methylmercury (MeHg) concentrations. While most of the Preserve has very low levels of sulfate, much higher concentrations are found in canals outside the Preserve, especially the L28. Restoration plans call for diverting water from the L28 into BCNP to increase water levels. However, the resulting increased sulfate load entering the Preserve in this canal water may have the unwanted effect of stimulating MeHg production and bioaccumulation here. To test this hypothesis we propose to conduct limited mesocosm studies of MeHg production in response to increased sulfate loads in BCNP, similar to studies we have already conducted in the central Everglades. Results from these tests will provide managers with information on the effects of diverting water of high sulfate concentrations into BCNP, so that costs and benefits of this planned diversion can be assessed, and also provide possible confirmatory results for our other mesocosm studies.

(4) MeHg Production in the Coastal Zone - As mentioned above, there is a major disconnect between past work on mercury cycling (freshwater emphasis) and human exposure to methylmercury (primarily from consumption of marine fish). Work in FY06 will begin studies of the mechanisms by which MeHg is produced in the coastal zone of the greater Everglades. Our initial survey of 12 mangrove sampling sites at the Shark River slough-ocean interface reveal the highest levels of MeHg in water ever seen in our extensive work on Hg in south Florida. Work in FY06 will seek to determine whether this was a one time, or short term, occurrence, or a more general condition that may be extremely important for understanding why marine fisheries in the Florida Bay and Gulf of Mexico region are commonly high in mercury.

(1) Sulfur Toxicity Experiment Mercury Sampling - This experiment will continue in FY06, with major sampling efforts in November 2004, and March and August 2006. This experiment tests the hypothesis that excess sulfate entering the Everglades from agricultural runoff results in the generation of high sulfide levels porewaters of affected areas, which by itself can exhibit toxicity, but also many secondary deleterious effects (e.g., suffocation, limitation of nutrient uptake). Sulfide toxicity has been shown in several environments to negatively impact freshwater aquatic plants. This experiment will test the hypothesis that excess sulfate entering the Everglades from agricultural runoff has a significant effect on many native macrophytes in the ecosystem, but that cattail is largely robust to sulfide toxicity. Although the primary emphasis on this experiment is to evaluate the possible toxicity of sulfide on native Everglades vegetation, the opportunity to study the sulfur loading effects on Hg methylation and bioaccumulation is obvious. Sampling conducted in the mesocosms will help to confirm or refute this hypothesis.

(2) Although our mesocosm tests to date have focused on the factors known to exacerbate (or speed) methylation in the environment, these test chambers can be equally well adapted for testing whether there may be solutions to the problem. Mercury methylation is almost entirely regulated by microbial processes, and as such competing processes, or those that limit mercury uptake, are certainly possible. Recent literature on test-tube scale incubations under laboratory conditions suggest that selenium and iron [Fe(III)] additions may prove useful in some situations for limiting methylmercury production. Such a strategy may prove useful in a setting like the STAs, where downstream transport of de novo produced methylmercury is a concern ecologically, and for permit renewal. It is interesting to note that one common feature of the STAs that yield little or no excess methylmercury is that excess iron that is also present. For this part of the task we will conduct a limited number of trial Fe(III) and selenium (added as sodium selenite). For selenium, hypothesize that an important mechanism diminishing the availability of mercury to aquatic food webs occurs through complex interactions between insoluble mercury selenides that may result in long-term retirement of mercury from actively cycling (and bioaccumulating) pools in the environment. We will investigate this hypothesis through study of the effects of graduated additions of small amounts of selenium to mercury-contaminated aquatic ecosystems and determine the impact of this supplemental selenium on accumulation of mercury at different trophic levels of indigenous food webs

(3) Methylation Controls in BCNP - Results from a preliminary water quality survey in BCNP conducted in FY04 and FY05 indicate that some areas of BCNP have higher than anticipated methylmercury (MeHg) concentrations. While most of the Preserve has very low levels of sulfate, much higher concentrations are found in canals outside the Preserve, especially the L28. Restoration plans call for diverting water from the L28 into BCNP to increase water levels. However, the resulting increased sulfate load entering the Preserve in this canal water may have the unwanted effect of stimulating MeHg production and bioaccumulation here. To test this hypothesis we propose to conduct limited mesocsom studies of MeHg production in response to increased sulfate loads in BCNP, similar to studies we have already conducted in the central Everglades. Results from these tests will provide managers with information on the effects of diverting water of high sulfate concentrations into BCNP, so that costs and benefits of this planned diversion can be assessed, and also provide possible confirmatory results for our other mesocosm studies.

(4) MeHg Production in the Coastal Zone - As mentioned above, there is a major disconnect between past work on mercury cycling (freshwater emphasis) and human exposure to methylmercury (primarily from consumption of marine fish). Work in FY06 will begin studies of the mechanisms by which MeHg is produced in the coastal zone of the greater Everglades. Our initial survey of 12 mangrove sampling sites at the Shark River slough-ocean interface reveal the highest levels of MeHg in water ever seen in our extensive work on Hg in south Florida. Work in FY06 will seek to determine whether this was a one time, or short term, occurrence, or a more general condition that may be extremely important for understanding why marine fisheries in the the Florida Bay and Gulf of Mexico region are commonly high in mercury.

Process_Date: Unknown
Process_Step:
Process_Description:
Work planned for FY07

To ensure comparability and interpretation of our results, the surveys will be conducted using the same sampling and analytical protocols developed under the ACME program. These include many mercury-free methods developed by the USGS and adopted worldwide. The data string for water, sediment and gambusia presently available for site 3A15 (from March 1995 through December 2006) is one of the longest and most well document data trend lines for mercury and methylmercury anywhere in the world. The fact that the data have been all derived from the same field crews and analytical lab adds considerable reliability and interpretability of the data, and have been the central data upon which many of our conclusions regarding the relative importance of the components of the mercury axis of evil (mercury, sulfate and carbon). We believe continuity of this data string is critical to infer how the restoration will affect the biogeochemistry of the Everglades. In addition, with the passage of national laws to reduce mercury emissions by 70%, trend lines like those at site 3A15 will be critical for providing direct evidence and quantifying the environmental benefits of such laws. Surveys conducted in portions of the Everglades not well covered by the ACME project will serve to provide an initial assessment of mercury/methylmercury contamination levels. Samples will be taken during early spring (February) and summer (July), when generally the annual low and high methylmercury levels are observed, respectively. All sampling efforts will include the collection of water, sediment, and gambusia, and will be analyzed using the low-level, mercury-speciation techniques applied by the USGS, Mercury Research Lab in Middleton, Wisconsin.

A limited number of coastal mangrove areas sampled in the summer of 2006 revealed some of the highest methylmercury levels ever seen by the USGS Mercury Research Lab (25 ng/L compared to Everglades typical interior marsh levels of about 0.05 to 0.50 ng/L). As of yet, no one has conducted a systematic study of the reasons underlying the very high levels of sport fish and commercial fish in Florida Bay, but the high levels observed in this initial survey would suggest the coastal, or near coastal zone, aquatic ecosystems could be a driving factor. For this part of our work plan, we will resample the locations sampled under the 2006 survey and add additional sites to our network to determine how generally applicable the initial observations are.

During FY05 and FY06, we participated in a multi-agency sponsored effort to evaluate the possible toxicological significance of sulfate loading on indigenous plants of the Everglades. Although this experiment was specifically designed to examine sulfate cycling and toxicity, it presented a good opportunity to extend our observations to assess the sulfur-dose methylmercury-production response curve. In December 2006, a final sampling effort was conducted, and in which we sampled all 32 mesocosms plus two additional ambient control sites. Samples for sediment, water and gambusia were collected, and presently in the sample queue at the USGS Mercury Research Lab.

The mesocosm experiments conducted under ACME Phase II were very useful for testing our overall hypotheses related to the controlling influence of sulfate, carbon and mercury in the methylmercury generation process. These experiments also provided quantitative estimates of the relative importance of each of these controlling components - the first time this has been done anywhere. However, we do not know how different our results may have been if the underlying substrate (peat in all our previous experiments) vary. For example, the marl prairies of ENP are largely refractory carbon and not as useable by microbial communities such as sulfate reducing bacteria. As such, ENP settings may have a greater response to added carbon that what we observed in the peat marshes of WCA 2 and WCA 3. The same could be true for the sandy substrate regions of BCNP. As part of the “Contaminant Synthesis” project, we will be compiling and publishing results from the previous mesocosm experiments. During this compilation and interpretation process, we will identify any critical needs or unanswered questions that those experiments generated. In addition, results from the surveys conducted in the FY07 will be available and used in combination with the previous mesocosm experiments to design a final round of mesocosm experiment that will likely be conducted ENP, BCNP or LNWR.

Process_Date: Unknown
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: David P. Krabbenhoft
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical address
Address: 8505 Research Way
City: Middleton
State_or_Province: WI
Postal_Code: 53562-3581
Country: USA
Contact_Voice_Telephone: 608 821-3843
Contact_Facsimile_Telephone: 608 821-3817
Contact_Electronic_Mail_Address: dpkrabbe@usgs.gov

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Heather S. Henkel
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: 600 Fourth St. South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: 727 803-8747 ext 3028
Contact_Facsimile_Telephone: 727 803-2030
Contact_Electronic_Mail_Address: hhenkel@usgs.gov
Resource_Description:
Geochemistry of Sulfur in the Florida Everglades: 1994 through 1999 (solid phase sulfur)
Distribution_Liability: The data have no implied or explicit guarantees
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: html
Format_Version_Number: unknown
Format_Information_Content:
The tables contain data by location for solid phase sulfur in WCA 1A, WCA 2A, Everglades Agricultural Area, Lake Okeechobee, and Taylor Slough
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table1.html>
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table2.html>
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table3.html>
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table4.html>
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table5.html>
Access_Instructions: Data may be downloaded form the SOFIA website
Fees: none

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Heather S. Henkel
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: 600 Fourth St. South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: 727 803-8747 ext 3028
Contact_Facsimile_Telephone: 727 803-2030
Contact_Electronic_Mail_Address: hhenkel@usgs.gov
Resource_Description:
Geochemistry of Sulfur in the Florida Everglades 1994 through 1999 (dissolved sulfate)
Distribution_Liability: The data have no implied or explicit guarantees
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: html
Format_Version_Number: unknown
Format_Information_Content:
The tables contain data for dissolved sulfate concentrations and isotopic compositions for surface water, rain water, and ground water.
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table6.html>
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table7.html>
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/01-007/table8.html>
Access_Instructions: Data may be downloaded form the SOFIA website
Fees: none

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Heather S. Henkel
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing address
Address: 600 Fourth St. South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: 727 803-8747 ext 3028
Contact_Facsimile_Telephone: 727 803-2030
Contact_Electronic_Mail_Address: hhenkel@usgs.gov
Resource_Description: Surface/Pore Water Chemistry
Distribution_Liability: The data have no implied or explicit guarantees
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: html tables
Format_Version_Number: unknown
Format_Information_Content:
The tables contain data for concentrations of dissolved chemical species in pore water from 12 cores collected at different sites in south Florida during 1994 and 1995
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/97-454/table3.html>
Network_Resource_Name: <https://sofia.usgs.gov/publications/ofr/97-454/table4.html>
Access_Instructions: Data may be downloaded from the SOFIA website
Fees: none

Metadata_Reference_Information:
Metadata_Date: 20110603
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Heather Henkel
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical address
Address: 600 Fourth Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: 727 803-8747 ext 3028
Contact_Facsimile_Telephone: 727 803-2030
Contact_Electronic_Mail_Address: sofia-metadata@usgs.gov
Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Access_Constraints: none
Metadata_Use_Constraints:
This metadata record may have been copied from the SOFIA website and may not be the most recent version. Please check <https://sofia.usgs.gov/metadata> to be sure you have the most recent version.

This page is <https://sofia.usgs.gov/metadata/sflwww/int_geochem.html>

U.S. Department of the Interior, U.S. Geological Survey
Comments and suggestions? Contact: Heather Henkel - Webmaster
Generated by mp version 2.8.18 on Fri Jun 03 11:55:59 2011