south florida ecosystem assessment: monitoring for adaptive … · 2014-03-11 · 2). today,...

The South Florida Ecosystem Assessment is being accomplished through the cooperation of federal andstate natural resource agency specialists. The agencies include the US Environmental Protection Agency,the US Fish and Wildlife Service, the US Geological Survey, the US National Park Service, the FloridaDepartment of Environmental Protection, the South Florida Water Management District, and the FloridaGame and Freshwater Fish Commission. Florida International University Southeast Environmental ResearchProgram is also a partner in this effort.

EPA 904-R-96-008December 1996

SOUTH FLORIDAECOSYSTEM ASSESSMENTMONITORING FOR ADAPTIVE MANAGEMENT:

IMPLICATIONS FOR ECOSYSTEM RESTORATION(Interim Report)

byJerry Stober, Project Manager

U.S. Environmental Protection Agency Region 4Science and Ecosystem Support Division

Athens, GA

Daniel Scheidt, Assistant Project ManagerU.S. Environmental Protection Agency Region 4

Water Management DivisionAtlanta, GA

Ron JonesFlorida International University

Southeast Environmental Research ProgramMiami, FL

Kent ThorntonFTN Associates, Ltd.

Little Rock, AR

Robert AmbroseU.S. Environmental Protection Agency

National Health and Environmental Exposure Research LaboratoryAthens, GA

Danny FranceU.S. Environmental Protection Agency Region 4

Science and Ecosystem Support DivisionAthens, GA

South Florida Ecosystem Assessment Report

The purpose of this interim report is to introduce the systemwide(4000-square-mile) scope of the monitoring project in the Evergladesecosystem and to present prel iminary f indings on the mercurycontamination, eutrophication, habitat alteration, and hydropatternmodification issues. The greatest threat to the Everglades ecosystem is toassume these issues are independent. The monitoring in this projectstrongly supports the federal and state Everglades restoration efforts andwill provide a means to evaluate present and future management actions.This project is focused on the ecological risk assessment process andguided by a set of policy relevant questions. A statistical survey design wasused to select 200 canal and 500 marsh sampling stations, a quarter ofwhich were sampled during successive wet and dry seasons over twoyears. These data allow quantitative estimation of the relative risk to theecological resources from multiple environmental threats. Marshmonitoring has been conducted during two years, one of which was thewettest year on record. To determine the range of natural variance tosupport and validate mercury modeling, process studies, and futureassessments, this monitoring should continue.

The highest mercury concentrations in algae, fish, and great egretshave been found to occur in Water Conservation Area 3 between AlligatorAlley and Tamiami Trail. No single point source has been identified thatcontributes directly to these high mercury levels. Atmospheric mercuryloading from precipitation is from 35 to 70 times greater in the publiclyowned Everglades than mercury loading in canal water coming from theEverglades Agricultural Area. Incineration in the urban areas is likely theprimary source of atmospheric mercury.

Several policy and management implications arose from thesepreliminary results including: (1) the current chronic mercury aquatic lifecriterion is underprotective and needs to be revised; (2) dischargingphosphorus at the current initial control target of 50 ppb will continue toallow eutrophication of over 95% of the Everglades marshes; and (3)ecological restoration must consider hydropattern modification, nutrientloading, mercury cycling, and habitat alteration simultaneously, notindependently.

Comparative ecological risk assessment is a critical element in adaptivemanagement for ecosystem restoration. This ecosystem assessmentproject provides a critical framework and foundation for assessing theeffectiveness of Everglades ecosystem restoration activities into the 21stcentury.

EXECUTIVE SUMMARY

i


Contents

INTRODUCTION ................................... 1 SOUTH FLORIDA EVERGLADES ....... 1 ISSUES................................................ 3 US EPA REGION 4 ECOSYSTEM ASSESSMENT PROJECT ................ 7

HIGHLIGHTS ........................................ 11 EUTROPHICATION .............................11 MERCURY CONTAMINATION ............ 13 HABITAT ALTERATION ...................... 17 HYDROPATTERN MODIFICATION ..... 18

ECOSYSTEM RESTORATIONTOOLS ................................................. 19

POLICY AND MANAGEMENTIMPLICATIONS .................................... 21 WATER QUALITY .............................. 21 AIR QUALITY...................................... 23 ASSESSING THE RISK ..................... 23

ON-GOING AND FUTURE STUDIES.. 25

US EPA REGION 4

SOUTH FLORIDAECOSYSTEMASSESSMENT

ii


PARTICIPANTS IN US EPA REGION 4

EVERGLADES ASSESSMENT PROJECT

US EPA Region 4Program Offices

APTMDL. Anderson-CarnahanD. DuboseL. PageORCP. Mancusi-Ungaro

SESDB. BerrangP. MeyerC. HalbrookM. ParsonsD. SmithW. McDanielM. WaskoJ. ScifresM. BirchP. MannT. SlagleT. StiberJ. DaveeD. ColquittD. KamensR. HowesG. CollinsJ. BrickerB. Noakes

FIU-SERPR. JaffeJ. TrexlerY. CaiA. AlliN. BlackI. MacFarlaneW. LoftusJ. Thomas

US EPA - Office of Researchand Development

EMAPR. LinthurstK. SummersT. OlsenNERL-RTPR. StevensR. BullockJ. Pinto

NERL-ATHENSR. AraujoC. BarberN. LouxL. Burns

ContractorsJ. Maudsley, MantechB. Lewis, MantechM. Weirich, MantechD. Stevens, MantechM. McDowell, MantechC. Laurin, FTN Associates, Ltd.J. Benton, FTN Associates, Ltd.R. Remington, FTN Associates, Ltd.S. Ponder, Integrated Laboratory SystemsK. Simmons, Integrated Laboratory SystemsS. Pilcher, Integrated Laboratory SystemsE. Crecelius, Battelle Marine SciencesB. Lasorsa, Battelle Marine Sciences

University of GeorgiaS. Rathbun

Florida Department ofEnvironmental ProtectionT. Atkeson

South Florida WaterManagement DistrictL. Fink

PHOTO CREDITS

ACKNOWLEDGEMENTS

US EPA Region 4 provided the cover photo. The USGS provided Figure 1. D. Scheidt of the US EPA contributedFigures 2, 3, 5, 6, 7, 12, 35, and 39. P. Meyer of the US EPA contributed to Figures 2 and 33. The US NPScontributed Figure 4. J. Stober of the US EPA provided Figures 11 and 37. T. Cawley provided Figure 13. P. Fredricksof the University of Florida provided the great egret data presented in Figure 26. The SFWMD provided Figure 36.

1


Figure 1. USGS satellite image of South Florida: lightareas on the east indicate urban areas; dark areas inthe center are the remnant Everglades; and the redarea at the top is the EAA.

1Marjory Stoneman Douglas. 1947. The Everglades: River of Grass. Banyan Books.

Sarasota, FL.

�They were changeless. They were changed1.�

SOUTH FLORIDA EVERGLADES

�There are no other Everglades in the world.They have always been one of the unique regionsof the earth. Nothing anywhere else is like them:Their vast glittering openness, wider than theenormous visible round of the horizon, the racingfree saltiness and sweetness of their massivewinds, under the dazzling blue heights of space1.�

The Florida Everglades is one of the largestfreshwater marshes in the world. Just onehundred years ago this vast wi ldernessencompassed over 4000 square miles, extending100 miles from the shores of Lake Okeechobeesouth to the coast. Subtle irregularities in groundelevation resulted in a mosaic of sawgrass marsh,wet prairies, sloughs, and tree islands. Theintermingling of temperate and Caribbean floracreated habitat for a variety of fauna, includingthe Florida panther, the alligator, and the hundredsof thousands of wading birds with which theEverglades were synonymous. The unique andtimeless characteristics of the Everglades weredescribed by Marjory Stoneman Douglas in herclassic work, The Everglades: River of Grass. This work brought theEverglades to national and international attention as a natural resourceworthy of preservation.

During the last century, the Everglades ecosystem has been altered toprovide for extensive agricultural and urban development (Figure 1). Today,50% of the historic Everglades wetlands have been drained, and an

INTRODUCTION

2


3


expanding South Florida human population of nearly 6 million competesfor this ecosystem�s water and land.

The Everglades changed dramatically as drainage canals were dug andagricultural and urban development increased in the 20th century. Mostof the remaining Everglades are in Loxahatchee National Wildlife Refuge,Everglades National Park, or the Water Conservation Areas (WCAs) (Figure2). Today, Everglades National Park includes only one-fifth of the originalriver of grass that once spread over more than 2 million acres. One-fourth of the historic Everglades is now in extensive agricultural productionwithin the 1000-square-mile Everglades Agricultural Area (EAA), wheresugar cane and vegetables are grown on fertile peat soils. Big CypressNational Preserve protects forested swamp resources within the Evergladeswatershed. Although half of the 16,000-square-mile Everglades watershedis in public ownership, there are a number of environmental issues thatmust be resolved to restore and protect the Everglades ecosystem,including eutrophication; mercury contamination of gamefish, wading birds,and other top predators; habitat alteration and loss; hydropatternmodification; water supply conflicts; endangered species; and nuisanceexotic species introductions.

ISSUES

Eutrophication

Nutrient loading from the Everglades Agricultural Areaand urban areas has signif icantly increased nutrientconcentrations, particularly phosphorus, in the downstreamWater Conservation Areas and the Park, resulting in majoreutrophic impacts to these wetland systems (Figure 3).Among the progressive Everglades eutrophic impacts areincreased soil phosphorus content, changed naturalperiphyton communities, increased oxygen-demandingorganic matter, loss of water dissolved oxygen, loss of native sawgrassplant communities, loss of important wading bird foraging habitat, andconversion of wet prairie plant communities to cattails. These collectivechanges are systemic and impact the structure and function of the aquatic

Figure 3. Eutrophication promotes cattailexpansion.

4


system. The Florida Department of EnvironmentalProtection (FDEP) has concluded that eutrophication of theEverglades results in the violation of four Florida waterquality standards to protect fish and wildlife and creates animbalance in natural populations of aquatic flora and fauna,with a resulting loss in biological integrity. Some eutrophicimpacts, such as periphyton community changes, arethought to be short-term and reversible if nutrient additions

can be significantly decreased. Other impacts are considered long-term(decades), such as loading peat soil with excess phosphorus that triggersthe loss of native plant communities and foraging habitat. The nutrientlevels required to sustain the natural balance of oligotrophic plants andanimals into future decades and centuries are currently under debate.There are still many marsh areas where natural water phosphorusconcentrations are less than 10 ppb. A combination of agricultural bestmanagement practices and construction of over 40,000 acres of wetlands(Stormwater Treatment Areas) are being implemented in an attempt tocontrol phosphorus loadings. The effectiveness of these controls in reducingnutrient concentrations to near historic levels, however, is not yet known.

Mercury Contamination

Many of South Florida�s fresh waters are under human healthfish consumption advisories because of mercury contamination inlargemouth bass and other top predator f ish. Mercuryconcentrations in an endangered Florida panther were high enoughto either have killed or contributed to the death of that panther in1989 (Figure 4). Wading bird populations today are about one-fifthof their abundance in the 1930s. Wading bird mercuryconcentrations also are high in certain Everglades areas, one ofmany factors that might be contributing to their decline (Figure 5).The sources and factors contributing to this mercury contaminationand bioaccumulation are not yet clearly understood. If the sourcesor critical processes can be identified, understood, and managed,the effects of mercury contamination may be reversible. Thisreversal, however, could take decades to realize even with effectivemanagement practices.

Figure 5. Wading birds haveelevated mercury levels.

Figure 4. Florida panther, an endangeredspecies, died from mercury toxicity.

5


Habitat Alteration and Loss

Over 1 million acres of the original River ofGrass have been drained and altered for other usessince the turn of the 20th century (Figure 6). Inaddition to the habitat lost, much of the remaininghabitat has been altered because of unnaturalflooding and drying, ground water removal, orsimilar perturbations. This habitat alteration is still ongoing as thepopulation of South Florida continues to expand. Unlike eutrophicationand mercury contamination, habitat loss is irreversible with certain landuses. In addition, habitat alteration aggravates other environmentalproblems, and these interactions are poorly understood.

Hydropattern Modification

Clearly, the greatest change that has occurredin the Everglades ecosystem is due to changing thehydropattern, or the depth, timing, and distributionof surface water, that occurred naturally in thesesystems (Figure 7). Wetland systems, by definition,are driven by water. Canal drainage systems, levees,f lood control structures, and water supplydiversions have collectively contributed to large-scale changes that have occurred in the Evergladesecosystem. The US Army Corps of Engineers in their Central and SouthernFlorida Project Re-Study is evaluating the modification of canals and leveesto return the hydropattern to a more natural regime. Determining thenatural flow regime and hydropattern and subsequently implementing therequired flows in the Everglades is a major restoration activity. �Drainingthe swamp� represents one of the greatest issues facing the Evergladesecosystem.

Endangered and Exotic Species

The South Florida ecosystem is known for its great diversity of plantsand animals, many of which are endangered. Florida also has a largenumber of introduced or nonnative fish and birds, which compete with

Figure 7. Extensive canal systems and watermanagement have modified the natural hydropat-tern.

Figure 6. Urban development has altered waterflow and habitat.

6


the native species. These introduced or exotic species are not restrictedto fauna; there are also significant numbers of nonnative plants. Themelaleuca tree, for example, has taken over large areas of the Everglades.This species was originally introduced because of its ability to transpirewater and help drain the wetland areas. Eliminating introduced speciesaltogether is unlikely, but practices for minimizing their impact on nativehabitat and preventing continued expansion into the Everglades areneeded.

Interaction Among Issues

None of the issues discussed above are independent of the others.These issues are all intertwined, each problem affecting other problems.Addressing these issues requires a large-scale perspective. Integrated andholistic studies of the multiple issues impacting the Everglades need tocompare the risks associated with all impacts and their interactions. TheUS EPA South Florida Ecosystem Assessment effort is a project thatprovides a foundation for addressing these issues and contributes to theInterAgency Task Force on Ecosystem Restoration efforts.

Ecosystem Restoration

Among the federal and state Everglades restoration efforts in progressare the EAA phosphorus control program and projects to restore waterdelivery (and ecology) throughout the Everglades. The present US EPASouth Florida Ecosystem Assessment effort integrates several importantrestoration issues and provides a critical science-based foundation forecosystem assessment and restoration. Long-term monitoring will providecritical baseline information to evaluate ecosystem restoration. Moreimportantly, continued monitoring is the only way to evaluate theeffectiveness of management strategies to improve ecological conditions.

The greatest threat to the Everglades ecosystem is to assumethe issues are independent.

7


US EPA REGION 4 SOUTH FLORIDA ECOSYSTEMASSESSMENT PROJECT

The US EPA Region 4 RegionalEnvironmental Monitoring and AssessmentProgram (REMAP) is an innovative, long-term research, monitoring and assessmentprogram designed to measure the currentand changing condit ion of ecologica lresources in South Florida. The ultimategoal of this program is to provide decisionmakers with sound ecological data toimprove environmental managementdecisions on multiple environmental issuesand restoration efforts. The Region 4 SouthFlorida Ecosystem Assessment Project usesthe US EPA ecological risk assessmentframework as a foundation for providingdecision makers with critical information(Figure 8). The program is guided by sevenpolicy-relevant questions:

(1) Magnitude - What is the magnitude of the mercury problem?(2) Extent - What is the extent of the mercury problem?(3) Trend - Is the problem getting better, worse, or staying the

same?(4) Cause - What factors are associated with or causing the

problem?(5) Source - What are the contributions and importance of

mercury from different sources?(6) Risk - What are the risks to different ecological systems and

species from mercury contamination?(7) Solutions - What management alternatives are available to

ameliorate or eliminate the mercury contamination problem?

Figure 8. Ecological Risk Assessment Framework. Ecologicalrisk assessment is a way of determining the likelihood ofadverse ecological effects from a pollutant or managementpractice.

8


The seven questions listed are equallyapplicable to each issue impacting theEverglades ecosystem, such as mercurycontamination, eutrophication, habitatalteration, or hydropattern modification.

The Region 4 project used a random,probability-based sampling strategy toselect sites for sampling *. Samples werecol lected from south of LakeOkeechobee to the mangrove fringe onFlorida Bay and from the ridge along theeastern coast into Big Cypress NationalPreserve on the west. The distributionof 200 canal samples is shown in Figure9 while the distribution of 500 marshsamples is shown in Figure 10. Thesamples represent the current ecologicalcondition in over 750 miles of canalsand in over 3000 square miles of marsh(over 2 million acres). The canals weresampled in September 1993, May andSeptember 1994, and May 1995. Themarshes were sampled in April andSeptember 1995 and May andSeptember 1996. This corresponds totwo dry (April and May) and two wet(September) seasons for both systemsover a two-year period. The projectsampling included water (Figure 11),canal sediment, marsh soil (Figure 12),fish (Figure 13), and algae at each canaland marsh sampling site location duringeach sampling period. The parameters

*Probability Samples:

Foundation For Regional

Risk Assessment

Probability samples are samples

where every member of the statistical

population has a known chance of being

selected and where the samples are drawn

at random. The project used a statistical

survey design in selecting its probability

samples so that the samples were drawn

in direct proportion to their occurrence in

the population; whether it was EAA or

WCA canals, sawgrass or cattail marshes,

or soil type. The measurements taken

can be used to estimate the proportion

(extent) and condition of that resource in

South Florida. The probability of selecting

the site is known and the site represents

that resource in an unbiased manner. The

sampling design is not biased to favor one

marsh type over another (e.g., sampling

only the marshes next to a road because

it was easier, or selecting a canal because

it looked good or bad). The risk to any of

the ecological resources from the multiple

environmental threats in South Florida is

a direct function of the extent and

magnitude of both the threat and the

ecological effects. Without probability

samples, these risks can not be realistically

estimated. Probability samples provide the

foundation for ecological risk assessment

in South Florida.

Figure 9. 200 sampling sites arelocated on over 750 canal miles.

Figure 10. 500 sampling sites arelocated on over 2 million marsh acres.

9


that were measured at each site can be used to answerquestions on multiple issues, including

In addition to the canal and marsh sampling, fourtransects established from the edge of a canal into the marshalong eutrophic gradients and the mercury load from sevencanal structures were also sampled.

The study is providing information critical to the SouthFlorida Ecosystem Restoration Task Force. The project isproviding information to answer the policy-relevantquestions raised above and to determine if the precursorand ecological success criteria identified by the Task Forceare being achieved.

This study permits a synoptic look at the ecologicalcondition of the entire freshwater canal and marsh systemin South Florida from Lake Okeechobee to the Floridamangrove systems. This large-scale perspective is neededto understand the impacts of different factors, such asphosphorus, mercury, habitat alteration, or hydropatternmodification, on the entire system rather than a small pieceor area. Looking only at isolated pieces in any given areaand extrapolating to South Florida would provide a distortedperspective. The statistical sampling approach permits

Figure 12. Soil cores were collected at eachof the marsh sites and analyzed for mercury,nutrients, and other constituents.

Eutrophication (e.g., Total phosphorus,catta i l , sawgrass, and per iphytondistribution)

Mercury contamination (e.g., mercury inwater, soil, algae, and mosquitofish)

Habitat alteration (e.g., plant communitydistributions throughout South Florida)

Hydropattern modification (e.g., waterdepth at all sites)

Figure 11. Helicopters and air boats wereused for sampling the marsh.

Figure 13. Mosquitofish were sampledbecause they are common in both the canals andthe marsh.

10


quantitative estimates, with knownconf idence, about populat ioncharacteristics, such as acres ofmarsh in cattails, percent of themarsh with fish mercury con-centrat ions greater than theproposed predator protectionlevel of 100 ppb (see page 14),or percent of the canal miles withtotal phosphorus concentrationsgreater than the Phase I controltarget level of 50 ppb. Studyinformation is a iding decisionmakers with its significant findingsrelated to the major issues facingecosystem restoration in SouthFlorida.

In addition to providing answers to policy relevant questions, theproject also is contributing to a better scientific understanding of theEverglades ecosystem. A holistic picture of soil thickness (Figure 14) orpercent organic matter (Figure 15) is not only scientifically important butalso provides insight into areas with peat subsidence and areas of organicsoils that might bind phosphorus or metals.

This study, while contributing to the development of adaptivemanagement practices, also provides the information needed to evaluatethe effectiveness of these management practices. For example, once thePhase I phosphorus control program is in place, phosphorus concentrationsthroughout the canal and marsh system can be reassessed to evaluate theeffectiveness of the control program.

The following is a summary of 1993-95 study highlights based on allfour canal sampling events (two wet and two dry seasons) and the firsttwo marsh sampling events (one wet and one dry season).

Figure 14. Thickness of the soilor peat deposits throughout themarsh.

Figure 15. Percent OrganicMatter in top soil throughout themarsh.

11


EUTROPHICATION

Historica l ly, the Evergladesecosystem was nutrient poor, withphosphorus concentrations lessthan 10 ppb over large areas.Increased total phosphorus con-centrations and eutrophicationhave been associated withdischarges from the EvergladesAgricultural Area into the Water

Conservation Areas, particularly the Refuge and Water Conservation Area2A. In 1995 about 45% of the canal miles (about 340 miles) in both thewet and dry seasons had total phosphorus concentrations greater thanthe Phase I control target of 50 ppb (Figures 16 and 17). In contrast only2% (wet season) to 5% (dry season) of the marsh area (about 39,000 to80,000 acres) had total phosphorus concentrations in excess of 50 ppb(Figures 18 and 19). It is clear the canals are delivering total phosphorusto the marsh.

Discharging phosphorus at the Phase Icontrol target of 50 ppb will continue to resultin eutrophicat ion of over 95% of theEverglades marshes. During the wet season,88% of the marsh (over 1.6 million acres)has a total phosphorus concentration of lessthan 25 ppb, or half this target concentration,and over 35% of the marsh has a totalphosphorus concentration less than 10 ppbduring the wet season.

HIGHLIGHTS

Discharging phosphorus at the Phase I control target of 50 ppb will continueto result in eutrophication of over 95% of the Everglades marshes.

Figure 17. South Florida canal water total phosphorusconcentrations distributions during the dry season.

Total P 25-50 ppb(34%)

Total P >50 ppb (46%)

Total P <10 ppb(2%)

Total P 10-25 ppb (18%)

Figure 16. South Florida canal water total phosphorusconcentrations distributions during the wet season.

Total P >50 ppb (44%)

Total P <10 ppb(11%)

Total P 10-25 ppb (25%)


12


Average total phosphorus concentrations in the canals are highest incanals north of Alligator Alley near and within the EAA (Figure 20). The

average total phosphorus concen-trations in the canals above AlligatorAlley are about 4 times higher than inthe marshes above Alligator Alley duringthe wet season (Figures 20 and 21).While the average total phosphorusconcentrations are similar in the canalsand marshes south of Tamiami Trail,delivery of total phosphorus loads fromthe Everglades Agricultural Area is notl imited just to the marshes aboveAlligator Alley (Figures 20 and 21). Totalphosphorus loads in the canals are beingtransported south into the Park (Figure22).

These elevated nutr ient con-centrations are also indicated by theabsence of an enzyme (a lka l inephosphatase) released by micro-organisms. The enzyme is producedonly when phosphorus concentrationsin the water are so low that growth islimited (Figure 23). A latitudinal pattern

Figure 18. South Florida marsh water (area-weighted) totalphosphorus concentrations distributions during the wet season.

Total P <10 ppb (37%)



Total P >50 ppb(2%)

Figure 19. South Florida marsh water (area-weighted) totalphosphorus concentrations distributions during the dry season.

Total P <10 ppb (25%)


Total P >50 ppb(5%)


North ofAlligator Alley

Alligator Alley toTamiami Trail

South ofTamiami Trail

MarshSeasonal Average Total Phosphorus, ppb

Figure 21. Water total phosphorus distribution in marsh fromnorth to south. Note: 50 ppb is the Phase I control target.




Figure 20. Water total phosphorus distribution in canals fromnorth to south. Note: 50 ppb is the Phase I control target.

CanalsSeasonal Average Total Phosphorus, ppb

13


exists from north to south across the marsh and also indicates the cleaninterior of the Refuge.

MERCURY CONTAMINATION

The REMAP program was initially designed toaddress mercury contamination in South Florida.Mosquitofish were selected as the indicator fishspecies because the fish are common throughout themarsh and canals, can be easily collected at allsampling sites, and are in the food chain for wadingbirds and sport fish. Largemouth bass are the popularsport fish and have high mercury concentrations, butare not found at every site, are more mobile, andare difficult to consistently collect in the marsh.

Once mercury enters the food chain, it increasesin concentration or biomagnifies at each higher stepor level in the food chain. The highest mercuryconcentrations are usually found in top predator fish(e.g., largemouth bass), birds, reptiles, and mammals

Figure 22. Pattern of marsh water total phosphorus concentrations.

Note: Hot spots near EAA, the Refuge, and the Park.

Figure 23. Microbial enzyme patterns.High enzyme values imply low phosphorusconcentrations in water.

14


that eat fish or fish-eating animals (e.g. raccoon, Florida panther). A predatorprotection level of 100 ppb mercury has been proposed by the US Fishand Wildlife Service and can be used as a criterion for comparison amongsystems and to determine potential exposure of largemouth bass and otherfish-eating animals to mercury.

In contrast to phosphorus, the highest mercuryconcentrations are found in the marshes and notthe canals. Over half the area in the marsh (68%or over 1 million acres) has mosquitofish withmercury concentrations that exceed 100 ppb(Figure 24). About 17% of the canal miles (about130 miles) have mosquitof ish with mercuryconcentrations that exceed the proposed predatorprotection level of 100 ppb (Figure 25). The highestconcentrations of methylmercury (the form ofmercury concentrated in the food chain) are foundnot only in fish and birds (Figure 26), but also inalgae in the marsh between Alligator Alley andTamiami Trail. The concentration of mercury inmarsh mosquitofish is significantly higher than theconcentration found in canal mosquitofish (Figures27 and 28).

Figure 26. Hot spot is the same for total mercury inmosquitofish and great egret feathers.

Figure 24. South Florida marsh (area-weigted)mosquitofish mercury concentration distributions.

Fish Hg > 250 ppb

(25%)

Fish Hg < 100 ppb (32%)

Fish Hg 100-250 ppb

(43%)

Figure 25. South Florida canal mosquitofishmercury concentration distributions.

Fish Hg > 250 ppb

(4%)

Fish Hg 100-250 ppb

(13%)

Fish Hg <100 ppb

(83%)

15


The marshes are the primaryareas of mercury contamination.For methylmercury to be formed,exactly the right combination ofenvironmental conditions mustoccur. Under the r ight set ofconditions of temperature, totalphosphorus, total organic carbon,sulfate, and pH, inorganic mercuryis converted by microorganisms tomethylmercury. This methyl-mercury enters the food chainprimarily through bioaccumulationby algae, bacteria, and other tinyorganisms that are eaten by largerorganisms. The right combinationof environmental conditions occursbetween Al l igator Al ley andTamiami Trail (Table 1). AboveAlligator Alley, the organic com-pounds and reduced sulfate (sulfide)might bind the mercury or methyl-mercury so it is not available foruptake by organisms. BelowTamiami Tra i l , lower concen-

The highest mercury concentrations in algae, fish, and Great Egrets all co-occurin Water Conservation Area 3 between Alligator Alley and Tamiami Trail.

Table 1Average Marsh and Canal Water Quality in Three Everglades Zones

Sulfate, ppm (mg/L)

Total Organic Carbon, ppm (mg/L)

Total Phosphorus, ppb (ug/L)

Constituents

Methylmercury, ppt (ng/L)

25

20

Marsh Canal Marsh Canal Marsh Canal

15

1278

26 17

16

7

18

24

11

14


Alligator Alleyto Tamiami Trail


0.6 0.2 0.4 0.2 0.2 0.1

9 327 4 8

Figure 27. Marsh mosquitofish mercury distribution from north to

south. Note: 100 ppb is proposed predator protection level.




Figure 28. Canal mosquitofish mercury distribution from north

to south. Note: 100 ppb is proposed predator protection level.




CanalsAverage Mosquitofish Mercury Concentrations, ppb

MarshAverage Mosquitofish Mercury Concentrations, ppb

16


trations of sulfate and total phosphorus are likely to limit the microbialmethylation and organic production rates, respectively. Between AlligatorAlley and Tamiami Trail, the concentrations of organic compounds andsulfide have decreased and probably no longer compete with themicroorganisms for mercury. In addition, phosphorus delivered from thecanals to the marsh in low concentrations may stimulate the growth ofperiphyton mats. Periphyton are attached algae common in the Evergladesecosystems. The USGS has found methylating bacteria associated withthese mats.

Increased product ion of a lga l mats may result in increasedmethylmercury production. This methylmercury then increases in thefood chain from algae up to wading bird nestlings and higher food chainlevels. The highest bioaccumulation in mosquitofish occurs betweenAlligator Alley and Tamiami Trail in both the canal and marsh habitats(Figures 27 and 28). However, mosquitofish also have high mercurycontamination in the marsh south of Tamiami Trail in the Park (Figure27). For methylmercury to accumulate up the food chain, the rightcombination of environmental conditions must exist and a complete foodchain for increased biomagnification at each level (Figure 29). The foodchain in the canals above Alligator Alley may not be sufficiently completeto accumulate mercury to concentrations above the predator protectionlevels because of increased eutrophication.

Figure 29. Bioaccumulation of mercury up the food chain from the water to wading birds andthe Florida panther.

17


HABITAT ALTERATION

One of the greatest human impacts in South Florida has been to thenatural habitat. Over 50% of the historic Everglades wetlands have beendrained. In addition to habitat loss, there has also been significant alterationof the remaining habitat. Because of eutrophication, about 4% (over77,000 acres) of the Everglades is now cattail marsh (Figure 30). At theturn of the 20th century, less than 1% of the marsh area was cattails.

Study results indicate that the Everglades marsh habitat (Figure 30)consists of 90% sawgrass and wet prairie communities and 4% cattail. Asecosystem restoration efforts proceed, such as phosphorus control ormodifications to hydropattern, these relative habitat percentages can bemonitored to assess the effectiveness of restoration efforts. Decreasedpercentages of cattail marsh can indicate decreased nutrient loading anddecreased eutrophication. Changes in the percentages of different habitattypes can also indicate an increase or decrease in the spread of exoticspecies, such as the melaleuca tree. There are other project habitatindicators that also provide information on other restoration issues (e.g.,percent dry area).

Figure 30. Current distribution of marsh typesfound in the South Florida Everglades.

Wet Prairie (46%)

Cattail (4%)

Pond (1%)

Cypress (5%)

Sawgrass (44%)

18


HYDROPATTERN MODIFICATION

The greatest change that has occurred in the Everglades ecosystem isthe change in surface water depth, distribution, and timing. The originalintent of the canals and levees was to �drain the swamp� so it could beused for agricultural production and urban development. A comparisonof a model simulation of the natural marsh water depth during a dryseason for the study area is shown in contrast to the actual measuredwater depths in the study area in April 1995 (Figure 31). Changing waterdepth also can significantly impact plants and animals. Wading birds, forexample, might not be able to forage because of increased depth whilesome fish species lose habitat because depths are too shallow. The presentponding of water in WCA-3A may influence the methylation of mercury.The cornerstone to Everglades restoration is hydrologic restoration.Without some semblance of the natural hydropattern in South Florida,the River of Grass and Big Cypress are unlikely to be protected or restored.

Ecological Restoration requires Hydropattern Restoration.

Figure 31. Comparison of current (left) vs. simulated natural marsh (right)water depths for the study area.

19


Mult ip le tools are required to resolve mult ip le interrelatedenvironmental issues. A number of tools are being used as part of theEverglades ecosystem restoration efforts, including mathematical models.To investigate the mercury contamination problem, for example, US EPAhas two models that are currently available. The Marsh Screening Model(Figure 32) is a large-scale Everglades ecosystem model with relativelysimple mercury cycling formulations that can be used to screen differentpolicy and/or management scenarios and evaluate their potential effectson reducing mercury contamination. A second model, BASS, is a foodchain model that provides insight on how mercury is bioaccumulatedthrough the food chain. BASS provides insight into the potential effects ofmercury on critical food chainswithin the Everglades ecosystem.US EPA is a lso developing adynamic mercury-cycling model,MERC5.

Other tools have been devel-oped by other agencies and arebeing used to address importantenvironmental issues, such ashydropattern modification. TheSouth Florida Water ManagementDistrict, for example, has devel-oped several hydrologic modelsthat are being used to evaluatedifferent management approachesfor restoring the natural hydrologyto the Everglades. One of thesemodels is ca l led the Natura lSystem Model. The Natura lSystem Model provides estimatesof what the hydrology might havebeen under various meteorological and climatic conditions before majordrainage efforts began (Figure 31). A second hydrologic model simulatescurrent conditions within the marsh ecosystem and provides a tool for

ECOSYSTEM RESTORATION TOOLS

Figure 32. Schematic showing the marsh screening model network.

20


evaluating the effects of different floodcontrol and water supply managementoptions on marsh hydrology. By using bothmodels and comparing and contrastingtheir output, managers can better assesswhich management approaches offeroptimal restoration options.

Other agencies also have developed tools that are being used in theEverglades ecosystem for different issues, such as eutrophication,atmospheric emissions, habitat alteration, and other problems. Whilemathematical modeling is one technology that is being pursued, this isnot the only set of tools in the toolbox. Improved and innovative fieldsampling techniques, more precise analytical procedures and use of remotesensing and satellite imagery are being used to investigate these issues.The US EPA, for example, conducted a major study to investigate mercuryemissions from municipal and medical waste incinerators (Figure 33) anda coal-fired cement kiln. They are in the process of evaluating the fate andtransport of this mercury and its possible deposition over the marsh (Figure34). The State of Florida, the Electric Power Research Institute, and theUS EPA established a deposition monitoring network to determine theatmospheric mercury forms and potential deposition to the marshthroughout South Flor ida. The USGS is conduct ing mercurybiogeochemical and bioaccumulat ion process studies. Modeling,monitoring, and process studies are complementary tools for addressingEverglades ecosystem issues. All of these tools and their information must

be integrated to develop man-agement approaches that will notonly restore and protect theEverglades but also satisfy thedifferent societal demands forwater supply, f lood control,agriculture, and urban devel-opment.

Figure 33. Waste incinerators are one of thesources of atmospheric mercury.

Figure 34. Fate and transport of mercury emissions fromthe source to the atmosphere and then deposited over themarsh.

21


WATER QUALITY

Mercury

The current water total mercury criterion for protectionof aquatic life is 12 parts per trillion (ppt). One hundredpercent of the Everglades marsh has total mercuryconcentrations less than 12 ppt. This criterion, therefore,is under-protective because wildlife effects have beenobserved and 100% of the Everglades is under a humanhealth fish consumption advisory. In addition, the predatorprotection criterion for mercury in prey species of 100ppb proposed by the US Fish and Wildlife Service isexceeded in over 65% of the marsh area. This indicates that alligators,raccoons, otters, endangered wading birds, other fish-eating animals, theFlorida panther, and humans are at risk from mercury contamination.

Mercury Loadings

South Florida Water Management District monitored total mercuryconcentrations biweekly at the pumps located on the canals surroundingthe Everglades Agricultural Area. Atmospheric deposition monitoring datawere collected at seven locations throughout South Florida. The datafrom these two monitoring programs were used to estimate the annualtotal mercury loads to the Everglades ecosystem (Table 2). Atmosphericdeposition in precipitation (Figure 35)contributed from 35 to 70 times themercury loading to the fresh waterEverglades compared to EvergladesAgricultural Area stormwater. It is notknown what proport ion of th isatmospheric deposition is of naturalversus anthropogenic origin. Atmos-pheric mercury source apportionmentstudies are scheduled for the next 4 to5 years.

AtmosphericDeposition

(Kg/yr)

EAA WaterDischarge

(Kg/yr)Year

2

3-4

1994

1995

Table 2Comparison of Atmospheric vs.Surface Water Mercury Loading

140

140

Figure 35. Wet deposition of mercury duringstorms is a major source of mercury to themarsh.

POLICY AND MANAGEMENT IMPLICATIONS

The current chronic mercury aquatic life criterion is underprotective.

22


Phosphorus

The Phase I interim phosphorus control target has beenestablished at a maximum of 50 ppb. However in 1995,97% of the marsh had total phosphorus concentrationsless than 50 ppb. In addition, over 88% of the marsh hadtotal phosphorus concentrations less than 25 ppb or halfthe Phase I total phosphorus control target. Dischargesfrom the Stormwater Treatment Areas at 50 ppb willcontinue to increase Everglades eutrophication (Figure 36).

Phosphorus-Mercury Interactions

The increased phosphorus concentrations measured in the Refuge,the Everglades Water Conservation Areas, and the Park are above naturalbackground concentrations and may aggravate the mercury problem byincreasing the biomass of the periphyton mats in which additional mercurymethylation might be occurring. Recent studies by the USGS have indicatedthat periphyton mats and associated microbial communities might serveas methylation sites for mercury. Because the historic Everglades were sonutrient-poor, there is a clear relationship between increased phosphorusand eutrophication, which can result in increased plant biomass, includingperiphyton. The effects of increased phosphorus cascade through theecosystem affecting more than just plant biomass. When productionexceeds some critical threshold, organic matter can bind mercury, makingless mercury avai lable for methylat ion. In addit ion, i f oxygenconcentrations go to zero because of decaying organic matter, sulfide canbe released that also binds mercury. Process and food web studies arerequired to further define the driving factors and associated environmentalconditions.

Figure 36. EAA stormwater dischargecontributes nutrients and mercury.

Discharges from the Stormwater Treatment Areas at 50 ppb will continueto cause Everglades eutrophication.

23


AIR QUALITY

Based on the deposition monitoring (Figure 37), emission studies,and an emissions inventory, the average mercury emissions for SouthFlorida are about 3 times higher than the state average. In SouthFlorida, the mercury deposition from precipitation downwind of theurban area is about 2 to 3 times the background level. The emissionsource studies indicate that municipal and medical waste incineratorsare the major atmospheric mercury emission sources in South Florida.The portion of deposited mercury that comes from local sources hasnot been determined. However, additional studies to provide betterestimates of natural mercury releases to the atmosphere are inprogress.

ASSESSING THE RISK

US EPA Region 4 is in the process ofconducting a comparative ecological riskassessment to determine which of theseenvironmental problems place theEverglades ecosystem at greatest risk. Thecomparative assessment is critical becausenone of the problems occurs independentlyof the others (Figure 38). Hydropatternmodification is a primary driver of all theproblems, but hydropattern can beinfluenced by habitat alteration. Both of theseproblems influence eutrophication andmercury contaminat ion and cyc l ing.Eutrophicat ion, through phosphorus

addition, is apparently contributing to the mercury problem, and all ofthese problems influence wildlife and the increased distribution of nuisance

Figure 38. Restoration issues are highly interde-pendent and must be addressed together.

Figure 37. Air depo-sition monitoring towersare located at 7 sitesthroughout South Florida.

Incineration, not natural sources, is the primary source of atmosphericmercury in South Florida.

24


exotic species. Assessing the risk to the ecological resources from themultiple environmental threats in South Florida requires a commonreference frame for estimating the extent and magnitude of both the threatand the ecological effects. The US EPA Ecosystem Assessment Project isthe first and only study, because of its sampling design and probabilitysamples, to provide a common reference frame for multiple environmentalthreats and effects. The spatial patterns of soil depth, phosphorus, fishmercury, and water depth, for example, represent the first such unbiasedsnapshots of the condition of the South Florida Everglades ecosystem.The consistent and comparable data from this study are critical for acomparative ecological risk assessment. Continued monitoring throughtime wil l permit these comparative risk estimates to be refined,contributing to better management decisions. In addition, the EcosystemRestoration Task Force has identified restoration success indicators (Table3). These indicators can be built into the monitoring program and can beused to evaluate different management options for ecosystem restoration.

The greatest threat to the Everglades ecosystem, however, is assumingthe problems facing the Everglades can be managed independently fromeach other. These problems are often interdependent and must beaddressed using holistic, adaptive management approaches. This formsthe foundation for the comparative ecological assessment of the relativerisks from each of the environmental problems.

Table 3Example Ecosystem Restoration Success Indicators

Problem Success Indicators

Hydropattern Modification

Habitat Alteration

Eutrophication

Mercury Contamination

Endangered Species

Reinstate system-wide natural hydropatterns and sheet flow

Increased spatial extent of wildlife corridors/greenways/flyways

Reduced phosphorus loading

Reduced top carnivore mercury body burden

Increased populations of threatened/endangered species

Comparative ecological risk assessment is a critical element of adaptivemanagement for ecosystem restoration.

25


ON-GOING AND FUTURE STUDIESUS EPA Region 4 has completed one full cycle of canal and marsh

sampling and is in the process of analyzing the information. This informationwill be used not only to answer the seven policy-relevant questions (page7) identified for mercury, but also to answer similar questions related tothe other environmental problems threatening the Everglades ecosystem(Figure 39). While this information provides a sound baseline forpreliminary answers to these questions, one of the wettest years on recordoccurred during the field sampling effort. Additional monitoring is essentialto determine the variability in the baseline patterns fromseason to season and the effect of this variability on futuremanagement decisions. Additional monitoring will increaseour ability to make statements about subareas in theEverglades ecosystem under different water managementregimes and will minimize the time required to detectchanges from adaptive management actions. Monitoringand iterative comparative ecological risk assessments shouldcontinue over the next 3 years as scientific understandingof the interactions among these problems develops.

The US EPA Region 4 monitoring network has beenredesigned based on the information collected to date. Thisredesign has decreased the number of samples to becollected in both canals and marshes without compromisingthe ability to make population estimates. In addition, thisredesign will permit both canal and marsh samples to becollected during the same sampling period in dry and wetseasons each year. This monitoring will provide informationon emerging trends in environmental problems and permit an evaluationof the effectiveness of any policy and management strategies implementedto fix these problems. Monitoring is the only approach that can be usedto assess the success and performance of management practices.

Figure 39. Fish consumption advi-sories apply to over 2 million acres ofwater in South Florida.

Monitoring is essential to understand the trends resulting fromadaptive management practices.

26


The US EPA Region 4 Ecosystem Assessment Project provides a criticalframework and foundation for assessing the effectiveness of Evergladesecosystem restoration activities into the 21st century.

The US EPA, a member of the South Florida Ecosystem RestorationTask Force, is contributing to other studies being conducted as part of therestoration effort. This project is contributing to on-going mercurybiogeochemistry and bioaccumulation process studies being conductedby the USGS. For example, the Region 4 Ecosystem Assessment Projecthas identified critical study areas in South Florida where process researchis needed to better understand the interrelationships among hydropatternmodifications, nutrient additions, and mercury cycling in the Evergladesecosystems. This project is also providing complementary monitoringinformation for simultaneous studies of atmospheric mercury emission,transport, and deposition in South Florida. In addition, the US EPA isworking with the SFWMD Everglades Nutrient Removal Project andStormwater Treatment Area Studies, the US Army Corps of EngineersCentral and Southern Florida Project Re-study, and Florida Departmentof Environmental Protection studies. The first comparative ecological riskassessment, incorporating results from these efforts, is planned for late1997.

south florida ecosystem assessment: monitoring for adaptive … · 2014-03-11 · 2). today,...

Documents