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Project Work Plan

Department of Interior USGS GE PES
Fiscal Year 2014 Study Work Plan

Study Title: Linking Land, Air and Water Management in the Southern Everglades and Coastal Zone to Water Quality and Ecosystem Restoration
Current Study Start Date: 10/01/13 Current Study End Date: 09/30/18
Location (Subregions, Counties, Park, or Refuge): Entire Evergaldes Ecosystem (Water Conservation Areas, Everglades National Park, Everglades Agricultural Area, Lake Okeechobee and associated rivers, adjacent marine zone in Gulf of Mexico and Florida Bay, Big Cypress National Preserve)
Funding Source: GEPES
Funding History: FY12; FY13
FY14 USGS Funding: FY14
Principal Investigator: David P. Krabbenhoft (dkrabbe@usgs.gov, 608.821.3843); William H Orem (borem@usgs.gov, 703.648.6273); George R. Aiken (graiken@usgs.gov, 303.541.3036)
USGS Project Officer: Nick Aumen, GEPES Coordinator
Supporting Organizations: ENP, USFWS, BCNP, SFWMD, FLDEP, USEPA, USACE

Overview & Objective(s): Water quality remains one of the biggest issues facing restoration of the Everglades. However, a complete understanding of all the factors (external and internal) that regulate past and present water quality in the Everglades, and to anticipate future water quality conditions that will occur in response to the restoration effort and climate change, is a significant challenge to both scientists and resource managers. Water quality studies in the Everglades over the past 10-20 years have largely focused on phosphorus (P) contamination and its ecological impacts. Mitigating P contamination includes the purchase of land to establish over 45,000 acres of storm water treatment areas (STAs) designed to remove P from water discharged into the ecosystem. Because so much attention has been focused on P in south Florida, water quality has become synonymous with P. While P remains a contaminant of concern for the Everglades, other contaminants also warrant attention so that the overall restoration goal of "...to improve the quantity, quality, timing, and distribution of clean fresh water needed to restore the South Florida Ecosystem" can be more generally and effectively achieved. An understanding of all the potential linkages between various pollutant sources, and physical and hydrologic changes resulting from the restoration will be needed to assure that water quality targets for the ecosystem are realized.

The USGS has been assessing two other important and synergistic contaminants, mercury (Hg) and sulfur (S), which due to aspects of their respective sources and transport ability, pose a threat to significantly larger portions of the ecosystem than P. Mercury, a long-range (dominantly form outside the south Florida region), atmospherically derived contaminant, affects the entire ecosystem. Sulfate, on the other hand, is dominantly derived from sources within the watershed (e.g., runoff from the EAA), but affects a larger fraction of the Everglades presently (about 60 percent) due to its greater mobility in the environment and because the STAs in their current configuration do nothing to abate sulfate transport to the downstream Everglades. Sulfate alone can have profound impacts on natural redox conditions in wetlands, which can, in turn, inducestress and/or kill native vegetation and benthic infauna. In addition, the co-contamination of the environment with Hg and sulfate has an extremely important synergistic effect on the toxicity of Hg through the conversion of inorganic Hg to methylmercury (MeHg), the most toxic and bioaccumulative form of Hg. Methylmercury comprises >95% of all the Hg in predator-level species. Wildlife toxicologists are still making many fundamental discoveries on the important ways that MeHg may be affecting fish and wildlife, including the new observations on White Ibis from the Everglades indicating that population level effects may be occurring through toxicity to the unborn, or through substantial hormone disruption (Dr. Peter Frederick, U. of Florida).

Mercury methylation in the Everglades, and the environment more generally, is dominantly the result of sulfate reducing bacteria (SRB), which utilize sulfate for natural processes, but that produce MeHg through cellular uptake of inorganic Hg and a recently discovered methyl-doner gene. Thus any actions that increase sulfate reduction (such as sulfate loading) or increase Hg availability (such as increases in Hg deposition) may serve to exacerbate Hg toxicity on ecosystems. In addition, seemingly unrelated activities like alterations to hydrologic cycles (wetting and drying periods), flushing rates, other water quality constituents (especially dissolved organic carbon [DOC], iron and pH), can have pronounced effects on Hg methylation. For example, oxidation of soils leads to in-situ conversion of organic sulfur to sulfate, and thus subsequent stimulation of sulfate reduction and methylation upon re-inundation. In addition, substantial amounts of DOC are also derived from EAA runoff and shows about the same aerial extent as sulfate. Our research has shown that DOC plays an important role in enhancing Hg availability to methylating microbes, but other important processes that may be affected by DOC concentration increases include light penetration limitation, nutrient uptake, and cycling of other exogenous metals. Lastly, another byproduct of sulfate reduction, sulfide, is deleterious to many freshwater wetland plants and infauna that are indigenous to the Everglades through oxygen deprivation and suffocation, limiting nutrient uptake, and or direct toxicity.

To this point, USGS studies on Hg and sulfate contamination in south Florida have largely focused on the water conservation areas (WCAs). Our studies have served as a template worldwide on how to conduct studies of Hg in the environment and why wetland-rich ecosystems are areas of heightened concern for MeHg exposure. In addition, our study demonstrated for the first time, the important linkages that exist between an air derived contaminant (Hg) and another from land-based sources (sulfate). Our project revealed a simultaneous large (>90%) decline of MeHg concentrations in all environmental compartments (water, sediment and biota) in central WCA3A-15, but no apparent change in other areas we monitor (WCA2A, WCA2B, and WCA1). Our data clearly showed that the MeHg declines were directly related to declines in sulfate levels in surface water resulting from changes to canal water pumping and delivery. In-situ mesocosm dosing tests at this site confirm that MeHg abundance is significantly and positively related to sulfate additions, without any additional Hg added. This observation poses the question whether there have been large declines in sulfur uses in the EAA, or changes in water routing internal to the Everglades. Since sulfate levels over time at our northern canal and WCA2 sites show similar or modestly lower levels of sulfate, we hypothesize that changes to water routing within the Everglades are responsible for the dramatically reduced sulfate levels at WCA3A that, in turn, have led to near-detection level concentrations of MeHg. If this is true, then we might expect that the sulfate-rich waters that previously flowed through our study site are now discharging elsewhere, likely south to Everglades National Park (ENP) or west to Big Cypress, where increased water delivery is a priority for the Restoration program. Indeed, evidence for steadily increasing fish Hg concentrations in the ENP over the past 5-10 years is available for at least one monitoring site, North Prong Creek (Ted Lange, Florida Fish and Wildlife Conservation Comission). However, since our research has focused primarily north of the ENP, we do not have contemporaneous water quality data to support or refute the conclusion that the increasing fish Hg levels are due to increasing sulfate loads due to increasing water delivery from canals to the Shark River Slough. We hypothesize that the increased delivery of sulfate-rich surface water to ENP will result in increases in MeHg production and bioaccumulation. The overall objective of this next phase of our research is to extend our understanding of the interactions of Hg, sulfate, DOC contamination to the entire Everglades ecosystem by including understudied areas including ENP (coastal or near coastal settings), Big Cypress, and Loxahatchee National Wildlife Refuge. In addition, we will seek to integrate our results into an ecosystem-scale model that can account for sulfate releases, transport within the ecosystem, loss to sulfate reduction and production of methylmercury.

In order to yield a reliable ecosystem scale model for sulfate-mercury interactions, we collect data that can be used for calibration and verification. That information is derived from field-intensives surveys conducted along surface water flow transects along which we measure key processes (sulfate reduction and MeHg production). An anticipated use of the model will be to help anticipate how future water use and distribution plans under CERP will affect the overall distribution and levels of sulfate and MeHg across the Everglades ecosystem.

A second research goal of our ongoing project is to provide an improved understanding of the complex biogeochmical controls on mercury methylation (synergistic and antagonistic) from interactions of mercury, sulfur and DOC. This continues to be a challenge worldwide among researchers, and our work is at the leading edge. Because the Everglades have been under a continuous state of change with regard to water use and water quality ("a living laboratory"), it is an ideal location to study the influences of ecosystem change on MeHg production and its impacts. As such we emphasize the use of these changes to attack several science objectives: (1) relate anthropogenic-induced changes in the water flow and chemistry on MeHg production, (2) understand how changes to water quality affect biogeochemical processes within the ecosystem affecting water chemistry, (3) provide predictive capability for the impacts of restoration-related changes on water chemistry, and (4) identify the impacts of contaminants on natural resources in the ecosystem. Our approach includes a combination of field surveys, contaminant monitoring at key sites, experimental studies in the ecosystem using experimental chambers (mesocosms), and laboratory experiments using microcosms. The experimental field and laboratory studies are utilized to confirm conceptual models and hypotheses developed from field surveys.

Study results will provide critical elements for building ecosystem models and screening-level risk assessment for the principal contaminants impacting water quality in the ecosystem (nutrients/sulfur/mercury/organics), and provide CERP (3005-1;3050-1,2,3,6,7,11;3060-1;3080-3,4,8,9,10), and GEER management with quantitative information for critical decisions, such as estimates of the maximum sulfur, nutrient, and mercury loads producing permissable levels of methylmercury in the ecosystem, the toxic effects of sulfur on biotic assemblages, estimates of the time required for ecosystem recovery from chemical contamination, and the effects of restoration on contaminant loads and impacts of contaminants. Results are incorporated into conceptual, mathematical, and risk assessment models of the Everglades ecosystem.

Specific Relevance to Major Unanswered Questions and Information Needs Identified:

This study supports several of the projects and overall goals listed in the DOI science plan. The DOI science plan lists three overarching restoration questions (page 9) that this study has direct relevance and provides information toward answering, including: (1) What actions will improve the quantity, timing, and distribution of clean fresh water needed to restore the South Florida ecosystem? (2) What actions will restore, protect, and manage natural resources on DOI lands in South Florida? (3) What actions will recover South Florida's threatened and endangered species? Aquifer Storage and Recovery (ASR) has substantial potential to affect water quality everywhere recovered water is released to the south Florida ecosystem, and is an area of concern in the DOI Science Plan (page 27). This study has demonstrated links between water quality characteristics of waters to be injected (sulfate, DOC, DO, and pH), the water quality characteristics of water recovered, and the water quality characteristics of water within the receiving surface and ground waters. In addition, the Comprehensive Integrated Water Quality Feasibility Study (CIWQFS; page 84) identifies degraded water bodies, types and sources of waterborne pollution, establishing load reduction targets for pollutants, and the need to improve water quality. Findings from this study will assist the DOI in providing needed information to multiagency CIWQFS Project Delivery Team in identifying the linkages between water quality targets and ecosystem restoration. The need to understand the sources, cycling and fate of critical chemical constituents like mercury, and to quantify the types and sources of pollution is stated on page 85. Linked to cycling and fate, the Science Plan cites the need for water quality performance targets (page 85) that can be used to evaluate the progress of restoration, and to identify areas in need of adaptive management. This project has shown clear linkages between water quality, land management (siting and operation of STAs; page 86), and restoration plans, which will be critical for evaluating the overall success of the Restoration effort. Finally, the Science Plan specifically identifies the need to predict the effects of hydroperiod alterations and soil and water chemistry on the bioavailability of mercury to methylation (page 89). This project not only discovered these hydro-cycle mercury-methylation linkages, but continues to unravel its complexities. The intent of these studies is to help land managers to make decisions that reduce the effects of hydroperiod alterations on mercury methylation.

Planned Products for FY14:

Orem W., Krabbenhoft D., and Aiken G. (2014) Modeling mercury, carbon and sulfur dynamics and biogeochemistry in the Florida Everglades. Goldschmidt Conference, August 2014, Sacramento, California. Program and Abstracts.

Aiken, G.R. (2014) Dissolved organic matter-metal interaction: Lessons learned from the study of mercury. Keynote address, Goldschmidt Conference, August 2014, Sacramento, California. Program and Abstracts.

Maglio, M., Krabbenhoft, D., Orem, W., Aiken, G., Tate, M., and DeWild, (2014), The effects of canal associated sulphate on methylmercury production and and bioaccumulation across Everglades National Park, to be submitted to Environmental Science and Technology.

Hart, K., and Krabbenhoft, D., (2014), Bioaccumulation of mercury and methylmercury in invasive pythons of the Everglades, in progress.

Gerbig,C.A., Kim, C.S., Stegemeier, J.P., Ryan, J.N., and Aiken, G.R. (2014) Effects of Kinetics, Sulfide Concentration, and Dissolved Organic Matter Characteristics on the Size and Structure of Metacinnabar-like Nanoparticles in Mercury-Dissolved Organic Matter-Sulfide Systems, in progress for Environmental Science and Technology.

Orem W.H., Fitz H.C., Krabbenhoft D.P., Tate M., Gilmour C., and Shafer M. (2014) Modeling Sulfate Transport and Distribution and Methylmercury Production Associated with Aquifer Storage and Recovery Implementation in the Everglades Protection Area. Sustainability of Water Quality and Ecology, submitted.

Orem W., Newman S., Osborne T.Z., and Reddy K.R. (2014) Projecting changes in Everglades soil biogeochemistry for carbon and other key elements, to possible 2060 climate and hydrologic scenarios. Environmental Management, submitted.

Orem W., Krabbenhoft D., and Aiken G. (2015) Sulfur, Mercury and other water quality parameters in an area of the northern Everglades affected by stormwater treatment area runoff. Journal of Environmental Quality, in preparation.

Work Plan

1. Monitoring

-Continue collaborative work initiated in 2008 with ENP to monitor sulfate intrusion into northern ENP and stimulation of MeHg production. Sampling of water and biota (Gambusia fish) is conducted by ENP. USGS personnel assist by processing samples on site and shipping back to USGS labs for chemical analysis of: mercury species, sulfur species, major anions and cations, nutrients, DOC and DOM, and metals. Continue monitoring of EAA canal water sufate, Hg, and other chemical species and historically studied sites in WCA1, WCA2, WCA3, and ENP to allow managers the ability to track the effects of the Restoration. This activity would be a once or twice a year sampling of our key locations. Monitoring of canals and marsh sites began in 1996 and a significant record of canal water chemistry has been developed. This data is included in the database published on SOFIA. In addition to our previous analyses, analysis of particulate sulfur, and dissolved organic sulfur will be conducted to fill data gaps. It is unknown how important particulate sulfur and dissolved organic sulfur are relative to sulfate in terms of total sulfur loading to the ecosystem.

2. Everglades Biogeochemistry

-Complete publication of effects of ASR on sulfate loading and MeHg. Risk (joint with USACE).

-Complete studies of changes in Hg, S, and DOC along flow path transects in WCAs 2A and western 3A. Work will include assessing the application of in-situ and boat mobilized water quality probes (pH, conductivity, chloride, redox, DO and DOC) at marsh and canal locations to better define seasonal changes in the import and transport of S, DOC and Hg into ENP and the MeHg response to this load. Ultimately, this effort will lead to the formulation of a linked water flow and water quality model that can be used to anticipate future occurrence and distributions of S, DOC, Hg and MeHg in response to various restoration scenarios for the Everglades.

-Initiate studies linking the biogeochemical fates of organic matter and sulfur along flow path transects in WCAs 2A and western 3A . This work will include assessing the effects of sulfide interactions with DOC and sediment organic matter on the retention of S along the flow path. The incorporation of sulfur into organic matter and the stability of the incorporated S to re-oxidation and mobilization will be evaluated in the field across a sulfate gradient in the Florida Everglades. This effort will lead to increased understanding of the fate of S in the system and provide necessary information for modeling the fate of sulfate in the Everglades.

-Collaborate with DEP and others to evaluate role of connate seawater is delivering chloride and sulfate to the ecosystem. Orem will participate in workshop on this issue in February 2014.

-Continue and expand the collaborations with ENP on Hg bioaccumulation in Burmese Pythons and Cape Sable Seaside Sparrow. Currently, Krabbenhoft, Hart, and Snow are writing a manuscript on the status and spatial trends of Hg in pythons. A second planned manuscript revealing the links to other Everglades organisms (Gambusia and Cape Sable Seaside Sparrow) is planned for FY15, as is a more detailed examination of the distribution of MeHg in specific organs of the pythons (particularly brain and liver tissues).

-Continue publication on Everglades biogeochemical studies (see planned publications list).

3. Coastal Zone

-Study Hg and MeHg transport in the coastal and offshore, especially the role of coastal dissolved organic matter (DOM) in complexing and stabilizing Hg species. This work is focused on the fate of Hg species from onshore sources to the offshore environment. This has implications for wildlife and human exposures to MeHg since the main exposure pathway for people is through marine fish consumption.

-Work with Eduardo Patino (USGS) on studies, of Hg, S and DOC transport to coastal areas, such as transport down Caloosahatchee River to discharge points near Cape Coral and Pine Island.

4. Climate Studies

-Investigate potential effects of climate change on Hg, S, and C biogeochemistry in the ecosystem. Participate in climate workshops on Everglades. Prepare publication based on initial workshop presentation.

-Work with Steve Davis (Everglades Foundation) and Tiffany Troxler (FIU) on studies of C accumulation in Everglades soil.

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