United States
Environmental Protection
Agency
Science and Ecosystem
Support Division
Region 4 and
Office of Research &
Development
EPA-904-R-96-008
December 1996
South Florida Ecosystem Assessment
Interim Report
\ AGRICULTURAL
h-LOXAHATCH6E
NATIONAL-
WILDLIFE REFUGE
-
-Wsf
Altigator 1 / WA
Alley NCONSERV.
V AREAS^
IBIG CYPRESS
I NATIONAL
PRESERVE
WCA-3A,
EVERGLADES
NATIONAL
Monitoring for
plications'
ptive Management:
'* stem Restoration
t-vt
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EPA 904-R-96-008
December 1996
SOUTH FLORIDA
ECOSYSTEM ASSESSMENT
MONITORING FOR ADAPTIVE MANAGEMENT:
IMPLICATIONS FOR ECOSYSTEM RESTORATION
(Interim Report)
by
Jerry Stober, Project Manager
U.S. Environmental Protection Agency Region 4
Science and Ecosystem Support Division
Athens, GA
Daniel Scheldt, Assistant Project Manager
U.S. Environmental Protection Agency Region 4
Water Management Division
Atlanta, GA
Ron Jones
Florida International University
Southeast Environmental Research Program
Miami, FL
Kent Thornton
FTN Associates, Ltd.
Little Rock, AR
Robert Ambrose
U.S. Environmental Protection Agency
National Health and Environmental Exposure Research Laboratory
Athens, GA
Danny France
U.S. Environmental Protection Agency Region 4
Science and Ecosystem Support Division
Athens, GA
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The South Florida Ecosystem Assessment is being accomplished through the cooperation of federal and
state 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 Florida
Department of Environmental Protection, the South Florida Water Management District, and the Florida
Game and Freshwater Fish Commission. Florida International University Southeast Environmental Research
Program is also a partner in this effort.
JB
FLORIM
u&
riSH iU'iUJI.LI E
SKKVJOK
Program
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South Florida Ecosystem Assessment Report
% OM = percent organic matter
CM = centimeter
FT = foot
KM = kilometer
kg/yr = kilogram per year
ppb = parts per billion (ug/L)
ppt = parts per trillion (ng/L)
ng/L = nanogram per liter (ppt)
mg/L = milligram per liter (ppm)
ug/kg = parts per billion (ppb)
uMol/hr = micromoles per hour
Hg = mercury
Hg° = elemental mercury
Hgll = inorganic mercury
MeHg = methylmercury
APTMD = Air, Pesticides, and Toxics Management Division
EAA = Everglades Agricultural Area
EMAP = Environmental Monitoring and Assessment Program
FID SERP = Florida International University Southeastern
Environmental Research Program
NHEERL-ATHENS = National Health and Environmental Exposure
Research Laboratory - Athens, GA
NHEERL - RTP = National Health and Environmental Exposure
Research Laboratory - Research Triangle Park, NC
NPS = National Park Service
ORC = Office of Regional Counsel
REMAP = Regional Environmental Monitoring and Assessment Program
SESD = Science and Ecosystem Support Division
SFWMD = South Florida Water Management District
US EPA = United States Environmental Protection Agency
USGS = United States Geological Survey
WCA = Water Conservation Area
BASS = Bioaccumulation and Aquatic System Simulator Model
MERCS = Mercury Cycling Model, Version 5
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South Florida Ecosystem Assessment Report
EXECUTIVE SUMMARY
The purpose of this interim report is to introduce the systemwide
(4000-square-mile) scope of the monitoring project in the Everglades
ecosystem and to present preliminary findings on the mercury
contamination, eutrophication, habitat alteration, and hydropattern
modification issues. The greatest threat to the Everglades ecosystem is to
assume these issues are independent. The monitoring in this project
strongly supports the federal and state Everglades restoration efforts and
will provide a means to evaluate present and future management actions.
This project is focused on the ecological risk assessment process and
guided by a set of policy relevant questions. A statistical survey design was
used to select 200 canal and 500 marsh sampling stations, a quarter of
which were sampled during successive wet and dry seasons over two
years. These data allow quantitative estimation of the relative risk to the
ecological resources from multiple environmenta threats. Marsh
monitoring has been conducted during two years, one of which was the
wettest year on record. To determine the range of natural variance to
support and validate mercury modeling, process studies, and future
assessments, this monitoring should continue.
The highest mercury concentrations in algae, fish, and great egrets
have been found to occur in Water Conservation Area 3 between Alligator
Alley and Tamiami Trail. No single point source has been identified that
contributes directly to these high mercury levels. Atmospheric mercury
loading from precipitation is from 35 to 70 times greater in the publicly
owned Everglades than mercury loading in canal water coming from the
Everglades Agricultural Area. Incineration in the urban areas is likely the
primary source of atmospheric mercury.
Several policy and management implications arose from these
preliminary results including: (I) the current chronic mercury aquatic life
criterion is underprotective and needs to be revised; (2) discharging
phosphorus at the current initial control target of 50 ppb will continue to
allow eutrophication of over 95% of the Everglades marshes; and (3)
ecological restoration must consider hydropattern modification, nutrient
loading, mercury cycling, and habitat alteration simultaneously, not
independently.
Comparative ecological risk assessment is a critical element in adaptive
management for ecosystem restoration. This ecosystem assessment
project provides a critical framework and foundation for assessing the
effectiveness of Everglades ecosystem restoration activities into the 21st
century.
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South Florida Ecosystem Assessment Report
Contents
US EPA REGION 4
SOUTH FLORIDA
ECOSYSTEM
ASSESSMENT
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 RESTORATION
TOOLS................................................. 19
POLICY AND MANAGEMENT
IMPLICATIONS 21
WATER QUALITY 21
AIRQUALITY 23
ASSESSING THE RISK 23
ON-GOING AND FUTURE STUDIES.. 25
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South Florida Ecosystem Assessment Report
ACKNOWLEDGEMENTS
PARTICIPANTS IN US EPA REGION 4
EVERGLADES ASSESSMENT PROJECT
US EPA Region 4
Program Offices
APTMD
L. Anderson-Carnahan
D. Dubose
L. Page
ORC
P Mancusi-Ungaro
SESD
B. Berrang
P Meyer
C. Hal brook
M. Parsons
D. Smith
W McDaniel
M.Wasko
J. Scifres
M. Birch
PMann
T. Slagle
T. Stiber
J. Davee
D. Colquitt
D. Kamens
R. Howes
G. Collins
J. Bricker
B. Noakes
US EPA - Office of Research
and Development
EMAP
R. Linthurst
K. Summers
T. Olsen
NERL-RTP
R. Stevens
R. Bullock
J. Pinto
NERL-ATHENS
R. Araujo
C. Barber
N.Loux
L. Burns
FIU-SERP
RJaffe
J. Trexler
Y.Cai
A. All
N. Black
I.MacFarlane
W. Loftus
I.Thomas
University of Georgia
S. Rathbun
Florida Department of
Environmental Protection
T. Atkeson
South Florida Water
Management District
L. Fink
Contractors
J.Maudsley, Mantech
B. Lewis, Mantech
M.Weirich, Mantech
D. Stevens, Mantech
M. McDowell, Mantech
C. Laurin, FTN Associates, Ltd.
J. Benton, FTN Associates, Ltd.
R. Remington, FTN Associates, Ltd.
S. Ponder; Integrated Laboratory
Systems
K. Simmons, Integrated Laboratory
Systems
S. Pilcher, Integrated Laboratory
Systems
E. Crecelius, Battelle Marine Sciences
B. Lasorsa, Battelle Marine Sciences
PHOTO CREDITS
US EPA Region 4 provided the cover photo. The USGS provided Figure I. D. Scheldt of the US EPA contributed
Figures 2, 3, 5, 6, 7, 12, 35, and 39. R Meyer of the US EPA contributed to Figures 2 and 33. The US NPS
contributed Figure4.J. StoberoftheUSEPAprovided Figures I I and37.T. Cawleyprovided Figure 13. PFredricks
of the University of Florida provided the great egret data presented in Figure 26. The SFWMD provided Figure 36.
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South Florida Ecosystem Assessment Report
INTRODUCTION
SOUTH FLORIDA EVERGLADES
"There are no other Everglades in the world.
They have always been one of the unique regions
of the earth. Nothing anywhere else is like them:
Their vast glittering openness, wider than the
enormous visible round of the horizon, the racing
free saltiness and sweetness of their massive
winds, under the dazzling blue heights of space1."
The Florida Everglades is one of the largest
freshwater marshes in the world. Just one
hundred years ago this vast wilderness
encompassed over 4000 square miles, extending
00 miles from the shores of Lake Okeechobee
south to the coast. Subtle irregularities in ground
elevation resulted in a mosaic of sawgrass marsh,
wet prairies, sloughs, and tree islands. The
intermingling of temperate and Caribbean flora
created habitat for a variety of fauna, including
the Florida panther, the alligator, and the hundreds
of thousands of wading birds with which the
Everglades were synonymous. The unique and
timeless characteristics of the Everglades were
described by Marjory Stoneman Douglas in her
classic work, The Everglades: River of Grass. This work brought the
Everglades to national and international attention as a natural resource
worthy of preservation.
Figure 1. USGS satellite image of South Florida: light
areas on the east indicate urban areas; dark areas in
the center are the remnant Everglades; and the red
area at the top is the EAA.
"They were changeless. They were changed1
During the last century, the Everglades ecosystem has been altered to
provide for extensive agricultural and urban development (Figure ). Today,
50% of the historic Everglades wetlands have been drained, and an
1Marjory Stoneman Douglas. 1947. The Everglades: River of Grass. Banyan Books.
Sarasota, FL.
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South Florida Ecosystem Assessment Report
Everglades Ecosystem
LOXAHATCHEE
NATIONAL
WILDLIFE REFUGE
Wet Prairie
Floating Periphyton
Wot Prairie -
Sawgrass Marsh
Cypress Forest
Figure 2, Everglades ecosystem commuriilies
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South Florida Ecosystem Assessment Report
expanding South Florida human population of nearly 6 million competes
for this ecosystem's water and land.
The Everglades changed dramatically as drainage canals were dug and
agricultural and urban development increased in the 20th century. Most
of the remaining Everglades are in Loxahatchee National Wildlife Refuge,
Everglades National Park, orthe Water Conservation Areas (WCAs) (Figure
2). Today, Everglades National Park includes only one-fifth of the original
river of grass that once spread over more than 2 million acres. One-
fourth of the historic Everglades is now in extensive agricultural production
within the 1000-square-mile Everglades Agricultural Area (EAA), where
sugar cane and vegetables are grown on fertile peat soils. Big Cypress
National Preserve protects forested swamp resources within the Everglades
watershed. Although half of the 16,000-square-mile Everglades watershed
is in public ownership, there are a number of environmental issues that
must 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; hydropattern
modification; water supply conflicts; endangered species; and nuisance
exotic species introductions.
ISSUES
Eutrophication
Nutrient loading from the Everglades Agricultural Area
and urban areas has significantly increased nutrient
concentrations, particularly phosphorus, in the downstream
Water Conservation Areas and the Park, resulting in major
eutrophic impacts to these wetland systems (Figure 3).
Among the progressive Everglades eutrophic impacts are
increased soil phosphorus content, changed natural
periphyton communities, increased oxygen-demanding
organic matter, loss of water dissolved oxygen, loss of native sawgrass
plant communities, loss of important wading bird foraging habitat, and
conversion of wet prairie plant communities to cattails. These collective
changes are systemic and impact the structure and function of the aquatic
Figure 3. Eutrophication promotes cattail
expansion.
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South Florida Ecosystem Assessment Report
Figure 4. Florida panther, an endangered
species, died from mercury toxicity.
Figure 5. Wading birds have
elevated mercury levels.
system. The Florida Department of Environmental
Protection (FDEP) has concluded that eutrophication of the
Everglades results in the violation of four Florida water
quality standards to protect fish and wildlife and creates an
imbalance in natural populations of aquatic flora and fauna,
with a resulting loss in biological integrity. Some eutrophic
impacts, such as periphyton community changes, are
thought 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 triggers
the loss of native plant communities and foraging habitat. The nutrient
levels required to sustain the natural balance of oligotrophic plants and
animals into future decades and centuries are currently under debate.
There are still many marsh areas where natural water phosphorus
concentrations are less than 0 ppb. A combination of agricultural best
management practices and construction of over 40,000 acres of wetlands
(Stormwater Treatment Areas) are being implemented in an attempt to
control phosphorus loadings. The effectiveness ofthese controls in reducing
nutrient concentrations to near historic levels, however, is not yet known.
Mercury Contamination
Many of South Florida's fresh waters are under human health
fish consumption advisories because of mercury contamination in
largemouth bass and other top predator fish. Mercury
concentrations in an endangered Florida panther were high enough
to either have killed or contributed to the death of that panther in
1989 (Figure 4). Wading bird populations today are about one-fifth
of their abundance in the 930s. Wading bird mercury
concentrations also are high in certain Everglades areas, one of
many factors that might be contributing to their decline (Figure 5).
The sources and factors contributing to this mercury contamination
and bioaccumulation are not yet clearly understood. If the sources
or critical processes can be identified, understood, and managed,
the effects of mercury contamination may be reversible. This
reversal, however, could take decades to realize even with effective
management practices.
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South Florida Ecosystem Assessment Report
Figure 6. Urban development has altered water
flow and habitat.
Habitat Alteration and Loss
Over million acres of the original River of
Grass have been drained and altered for other uses
since the turn of the 20th century (Figure 6). In
addition to the habitat lost, much of the remaining
habitat has been altered because of unnatural
flooding and drying, ground water removal, or
similar perturbations. This habitat alteration is still ongoing as the
population of South Florida continues to expand. Unlike eutrophication
and mercury contamination, habitat loss is irreversible with certain land
uses. In addition, habitat alteration aggravates other environmental
problems, and these interactions are poorly understood.
Hydropattern Modification
Clearly, the greatest change that has occurred
in the Everglades ecosystem is due to changing the
hydropattern, orthe depth, timing, and distribution
of surface water, that occurred naturally in these
systems (Figure 7). Wetland systems, by definition,
are driven by water. Canal drainage systems, levees,
flood control structures, and water supply
, , I, ,. , -, , i
diversions have collectively contributed to large-
scale changes that have occurred in the Everglades
ecosystem. The US Army Corps of Engineers in their Central and Southern
Florida Project Re-Study is evaluating the modification of canals and levees
to return the hydropattern to a more natural regime. Determining the
natural flow regime and hydropattern and subsequently implementing the
required flows in the Everglades is a major restoration activity. "Draining
the swamp" represents one of the greatest issues facing the Everglades
ecosystem.
Endangered and Exotic Species
The South Florida ecosystem is known for its great diversity of plants
and animals, many of which are endangered. Florida also has a large
number of introduced or nonnative fish and birds, which compete with
Figure 7. Extensive canal systems and water
maunagement have modified tneynatural nydropat.
tern.
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South Florida Ecosystem Assessment Report
the native species. These introduced or exotic species are not restricted
to fauna; there are also significant numbers of nonnative plants. The
melaleucatree, for example, has taken over large areas of the Everglades.
This species was originally introduced because of its ability to transpire
water and help drain the wetland areas. Eliminating introduced species
altogether is unlikely, but practices for minimizing their impact on native
habitat and preventing continued expansion into the Everglades are
needed.
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 and
holistic studies of the multiple issues impacting the Everglades need to
compare the risks associated with all impacts and their interactions. The
US EPA South Florida Ecosystem Assessment effort is a project that
provides a foundation for addressing these issues and contributes to the
InterAgency Task Force on Ecosystem Restoration efforts.
The greatest threat to the Everglades ecosystem is to assume
the issues are independent.
Ecosystem Restoration
Among the federal and state Everglades restoration efforts in progress
are the EAA phosphorus control program and projects to restore water
delivery (and ecology) throughout the Everglades. The present US EPA
South Florida Ecosystem Assessment effort integrates several important
restoration issues and provides a critical science-based foundation for
ecosystem assessment and restoration. Long-term monitoring will provide
critical baseline information to evaluate ecosystem restoration. More
importantly, continued monitoring is the only way to evaluate the
effectiveness of management strategies to improve ecological conditions.
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South Florida Ecosystem Assessment Report
US EPA REGION 4 SOUTH FLORIDA ECOSYSTEM
ASSESSMENT PROJECT
The US EPA Region 4 Regional
Environmental Monitoring and Assessment
Program (REMAP) is an innovative, long-
term research, monitoring and assessment
program designed to measure the current
and changing condition of ecological
resources in South Florida. The ultimate
goal of this program is to provide decision
makers with sound ecological data to
improve environmental management
decisions on multiple environmenta issues
and restoration efforts. The Region 4 South
Florida Ecosystem Assessment Project uses
the US EPA ecological risk assessment
framework as a foundation for providing
decision makers with critical information
(Figure 8). The program is guided by seven
policy-relevant questions:
Ecological Risk Assessment
PROBLEM FORMULATION
Characterization of
Exposure -4* Ecological
Effects
^
RISK
^"
C
^" ^
HARACTERi;
^s
7.fl
w
JION
Figure 8. Ecological Risk Assessment Framework. Ecological
risk assessment is a way of determining the likelihood of
adverse ecological effects from a pollutant or management
practice.
Magnitude - What is the magnitude of the mercury problem?
Extent - What is the extent of the mercury problem?
Trend - Is the problem getting better, worse, or staying the
same?
Cause - What factors are associated with or causing the
problem?
Source - What are the contributions and importance of
mercury from different sources?
Risk - What are the risks to different ecological systems and
species from mercury contamination?
Solutions - What management alternatives are available to
ameliorate or eliminate the mercury contamination problem?
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South Florida Ecosystem Assessment Report
*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 EAAor
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
marshtype overanother(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 riskto 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.
The seven questions listed are equally
applicable to each issue impacting the
Everglades ecosystem, such as mercury
contamination, eutrophication, habitat
alteration, or hydropattern modification.
The Region 4 project used a random,
probability-based sampling strategy to
select sites for sampling *. Samples were
collected from south of Lake
Okeechobee to the mangrove fringe on
Florida Bay and from the ridge along the
eastern coast into Big Cypress National
Preserve on the west. The distribution
of 200 canal samples is shown in Figure
9 while the distribution of 500 marsh
samples is shown in Figure 10. The
samples represent the current ecological
condition in over 750 miles of canals
and in over 3000 square miles of marsh
(over 2 million acres). The canals were
sampled in September 993, May and
September 1994, and May 1995. The
marshes were sampled in April and
September 995 and May and
September 1996. This corresponds to
two dry (April and May) and two wet
(September) seasons for both systems
over a two-year period. The project
sampling included water (Figure I),
canal sediment, marsh soil (Figure 2),
fish (Figure 3), and agae at each canal
and marsh sampling site location during
each sampling period. The parameters
-K , -v (
"jWjb^T^
v*%-~}-
"S
"-^-r
Figure 9. 200 sampling sites are
located on over 750 canal miles.
Figure 10. 500 sampling sites are
located on over 2 million marsh acres.
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South Florida Ecosystem Assessment Report
that were measured at each site can be used to answer
questions on multiple issues, including
Eutrophication (e.g., Total phosphorus,
cattail, sawgrass, and periphyton
distribution)
Mercury contamination (e.g., mercury in
water, soil, agae, and mosquitofish)
Habitat alteration (e.g., plant community
distributions throughout South Florida)
Hydropattern modification (e.g., water
depth at all sites)
Figure 11. Helicopters and air boats were
used for sampling the marsh.
In addition to the canal and marsh sampling, four
transects established from the edge of a canal into the marsh
along eutrophic gradients and the mercury load from seven
canal structures were also sampled.
The study is providing information critical to the South
Florida Ecosystem Restoration Task Force. The project is
providing information to answer the policy-relevant
questions raised above and to determine if the precursor
and ecological success criteria identified by the Task Force
are being achieved.
This study permits a synoptic look at the ecological
condition of the entire freshwater canal and marsh system
in South Florida from Lake Okeechobee to the Florida
mangrove systems. This large-scale perspective is needed
to understand the impacts of different factors, such as
phosphorus, mercury, habitat alteration, or hydropattern
modification, on the entire system rather than a small piece
or area. Looking only at isolated pieces in any given area
and extrapolating to South Florida would provide a distorted
perspective. The statistical sampling approach permits
Figure 12. Soil cores were collected at each
of the marsh sites and analyzed for mercury,
nutrients, and other constituents.
Figure 13. Mosquitofish were sampled
because they are common in both the canals and
the marsh.
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South Florida Ecosystem Assessment Report
8! 26.20
Q
3
APRIL & SEPTEMBER 1395
COMBINED SEASONS
KA-
APRIL & SEPTEMBER 1995/^V,
COMBINED SEASONS 'k. '.\
fW"' /\ ",'
$yJi'~d- ''' ^Vj-J
ml*-
^Mf.
M.CO
20.00
10.09
D.ra
-31 00 -80.80 -80.60 -80.40
-81.00 -80.80 -8060 -80.40
LONGITUDE, degrees
Figure 14. Thickness of the soil Figure 15. Percent Organic
or peat deposits throughout the Matter in top soil throughout the
marsh. marsh.
quantitative estimates, with known
confidence, about population
characteristics, such as acres of
marsh in cattails, percent of the
marsh with fish mercury con-
centrations greater than the
proposed predator protection
level of 00 ppb (see page 4),
or percent of the canal miles with
tota phosphorus concentrations
greater than the Phase I control
target level of 50 ppb. Study
information is aiding decision
makers with its significant findings
related to the major issues facing
ecosystem restoration in South
Florida.
In addition to providing answers to policy relevant questions, the
project also is contributing to a better scientific understanding of the
Everglades ecosystem. A holistic picture of soil thickness (Figure 14) or
percent organic matter (Figure 15) is not only scientifically important but
also provides insight into areas with peat subsidence and areas of organic
soils that might bind phosphorus or metals.
This study, while contributing to the development of adaptive
management practices, also provides the information needed to evaluate
the effectiveness of these management practices. For example, once the
Phase I phosphorus control program is in place, phosphorus concentrations
throughout the canal and marsh system can be reassessed to evaluate the
effectiveness of the control program.
The following is a summary of 993-95 study highlights based on all
four canal sampling events (two wet and two dry seasons) and the first
two marsh sampling events (one wet and one dry season).
10
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South Florida Ecosystem Assessment Report
Total P >50 ppb (44%)
HIGHLIGHTS
EUTROPHICATION
Total P 25-50 ppb
(20%)
Total P 10-25 ppb (25%)
Figure 16. South Florida canal water total phosphorus
concentrations distributions during the wet season.
Historically, the Everglades
ecosystem was nutrient poor, with
Total P<10 ppb phosphorus concentrations less
(11%) K
than 10 ppb over large areas.
Increased total phosphorus con-
centrations and eutrophication
have been associated with
discharges from the Everglades
Agricultural Area into the Water
Conservation Areas, particularly the Refuge and Water Conservation Area
2A. In 995 about 45% of the canal miles (about 340 miles) in both the
wet and dry seasons had total phosphorus concentrations greater than
the Phase I control target of 50 ppb (Figures 16 and 7). In contrast only
2% (wet season) to 5% (dry season) of the marsh area (about 39,000 to
80,000 acres) had tota phosphorus concentrations in excess of 50 ppb
(Figures I 8 and 19). It is clear the canals are delivering tota phosphorus
to the marsh.
Discharging phosphorus at the Phase I
control target of 50 ppb will continue to result
in eutrophication of over 95% of the
Everglades marshes. During the wet season,
88% of the marsh (over 1.6 million acres)
has a total phosphorus concentration of less
than 25 ppb, or half this target concentration,
and over 35% of the marsh has a total
phosphorus concentration less than 10 ppb
during the wet season.
Total P >50 ppb (46%)
Total P 25-50 ppb
(34%)
Total P<10 ppb
(2%)
Total P 10-25 ppb (18%)
Figure 17. South Florida canal water total phosphorus
concentrations distributions during the dry season.
Discharging phosphorus at the Phase I control target of 50 ppb will continue
to result in eutrophication of over 95% of the Everglades marshes.
11
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South Florida Ecosystem Assessment Report
Total P 10-25
(51%)
ppb
Total P 25-50 ppb
(10%)
Total P >50 ppb
(2%) <35%>
Total P<10 ppb (37%)
Figure 18. South Florida marsh water (area-weighted) total
phosphorus concentrations distributions during the wet season.
Total P 1 0'25
Total P 25-50 ppb
(35%)
Total P >50 ppb
(5%)
Total P<10 ppb (25%)
Figure 19. South Florida marsh water (area-weighted) total
phosphorus concentrations distributions during the dry season.
Average total phosphorus
canals north of Alligator Alley
Canals
Seasonal Average Total Phosphorus, ppb
North of
Alligator Alley
Alligator Alleyto
Tamiami Trail
South of
Tamiami Trail
Wet
| Dry
Figure 20. Water total phosphorus distribution in canals from
north to south. Note: 50 ppb is the Phase I control target.
Marsh
Seasonal Average Total Phosphorus, ppb
North of
Alligator Alley
Alligator Alley to
Tamiami Trail
South of
Tamiami Trail
Wet
Dry
concentrations in the canals are highest in
near and within the EAA (Figure 20). The
average total phosphorus concen-
trations in the canals above Alligator
Alley are about 4 times higher than in
the marshes above Alligator Alley during
the wet season (Figures 20 and 2 ).
While the average total phosphorus
concentrations are similar in the canals
and marshes south of Tamiami Trail,
delivery of total phosphorus loads from
the Everglades Agricultural Area is not
limited just to the marshes above
Alligator Alley (Figures 20 and 2 I). Total
phosphorus loads in the canals are being
transported south into the Park (Figure
22).
These elevated nutrient con-
centrations are also indicated by the
absence of an enzyme (alkaline
phosphatase) released by micro-
organisms. The enzyme is produced
only when phosphorus concentrations
in the water are so low that growth is
limited (Figure 23). A latitudinal pattern
Figure 21. Water total phosphorus distribution in marsh from
north to south. Note: 50 ppb is the Phase I control target.
12
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South Florida Ecosystem Assessment Report
|, IK
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Figure 22. Pattern of marsh water total phosphorus concentrations.
Note: Hot spots near EAA, the Refuge, and the Park.
a i to
LONGITUDE.
Figure 23. Microbial enzyme patterns.
High enzyme values imply low phosphorus
concentrations in water.
exists from north to south across the marsh and also indicates the clean
interior of the Refuge.
MERCURY CONTAMINATION
The REMAP program was initially designed to
address mercury contamination in South Florida.
Mosquitofish were selected as the indicator fish
species because the fish are common throughout the
marsh and canals, can be easily collected at all
sampling sites, and are in the food chain for wading
birds and sport fish. Largemouth bass are the popular
sport fish and have high mercury concentrations, but
are not found at every site, are more mobile, and
are difficult to consistently collect in the marsh.
Once mercury enters the food chain, it increases
in concentration or biomagnifies at each higher step
or level in the food chain. The highest mercury
concentrations are usually found in top predator fish
(e.g., largemouth bass), birds, reptiles, and mammals
13
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South Florida Ecosystem Assessment Report
Fish Hg100-250 ppb
(43%)
Fish Hg> 250 ppb
(25%)
Fish Hg> 250 ppb
(4%)
Fish Hg 100-250 ppb
(13%)
Fish Hg< 100 ppb (32%)
Figure 24. South Florida marsh (area-weigted)
mosquitofish mercury concentration distributions.
FishHg<100ppb
(83%)
Figure 25. South Florida canal mosquitofish
mercury concentration distributions.
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that eat fish or fish-eating animals (e.g. raccoon, Florida panther). A predator
protection level of 100 ppb mercury has been proposed by the US Fish
and Wildlife Service and can be used as a criterion for comparison among
systems and to determine potential exposure of largemouth bass and other
fish-eating animals to mercury.
In contrast to phosphorus, the highest mercury
concentrations are found in the marshes and not
the canals. Over half the area in the marsh (68%
or over million acres) has mosquitofish with
mercury concentrations that exceed I 00 ppb
(Figure 24). About 17% of the canal miles (about
30 miles) have mosquitofish with mercury
concentrations that exceed the proposed predator
protection level of 100 ppb (Figure 25). The highest
concentrations of methylmercury (the form of
mercury concentrated in the food chain) are found
not only in fish and birds (Figure 26), but also in
a gae in the marsh between Alligator Alley and
Tamiami Trail. The concentration of mercury in
marsh mosquitofish is significantly higher than the
concentration found in canal mosquitofish (Figures
27 and 28).
Me
laaa
OH H-o
Figure 26. Hot spot is the same for total mercury in
mosquitofish and great egret feathers.
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South Florida Ecosystem Assessment Report
The highest mercury concentrations in algae, fish, and Great Egrets all co-occur
in Water Conservation Area 3 between Alligator Alley and Tamiami Trail.
The marshes are the primary
areas of mercury contamination.
For methyl mercury to be formed,
exactly the right combination of
environmental conditions must
occur. Under the right set of
conditions of temperature, total
phosphorus, tota organic carbon,
sulfate, and pH, inorganic mercury
is converted by microorganisms to
methylmercury. This methyl-
mercury enters the food chain
primarily through bioaccumulation
by algae, bacteria, and other tiny
organisms that are eaten by larger
organisms. The right combination
of environmental conditions occurs
between Alligator Alley and
Tamiami Trail (Table I). Above
Alligator Alley, the organic com-
pounds and reduced sulfate (sulfide)
might bind the mercury or methyl-
mercury so it is not available for
uptake by organisms. Below
Tamiami Trail, lower concen-
Marsh
Average Mosquitofish Mercury Concentrations, ppb
o ioa
:: :
North of
Alligator Alley
Alligator Alley to
Tamiami Trail
South of
Tamiami Trail
Figure 27. Marsh mosquitofish mercury distribution from north to
south. Note: 100 ppb is proposed predator protection level.
Canals
Average Mosquitofish Mercury Concentrations, ppb
0 i Oil 2 DO
North of
Alligator Alley
Alligator Alley to
Tamiami Trail
South of
Tamiami Trail
Figure 28. Canal mosquitofish mercury distribution from north
to south. Note: 100 ppb is proposed predator protection level.
Table 1
Average Marsh and Canal Water Quality in Three Everglades Zones
North of
Alligator Alley
Marsh Canal
Constituents
Total Phosphorus, ppb (ug/L) 20 78
Total Organic Carbon, ppm(mg/L) 25 26
Sulfate, ppm (mg/L) 9 27
Methylmercury, ppt(ng/L) 0.6 0.2
Alligator Alley South of
to Tamiami Trail Tamiami Trail
Marsh Canal Marsh Canal
16
17
4
0.4
24
18
7
0.2
12
15
3
0.2
14
11
8
0.1
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South Florida Ecosystem Assessment Report
trations of sulfate and total phosphorus are likely to limit the microbial
methylation and organic production rates, respectively. Between Alligator
Alley and Tamiami Trail, the concentrations of organic compounds and
sulfide have decreased and probably no longer compete with the
microorganisms for mercury. In addition, phosphorus delivered from the
canals to the marsh in low concentrations may stimulate the growth of
periphyton mats. Periphyton are attached algae common in the Everglades
ecosystems. The USGS has found methylating bacteria associated with
these mats.
Increased production of algal mats may result in increased
methylmercury production. This methylmercury then increases in the
food chain from algae up to wading bird nestlings and higher food chain
levels. The highest bioaccumulation in mosquitofish occurs between
Alligator Alley and Tamiami Trail in both the canal and marsh habitats
(Figures 27 and 28). However, mosquitofish also have high mercury
contamination in the marsh south of Tamiami Trail in the Park (Figure
27). For methylmercury to accumulate up the food chain, the right
combination of environmental conditions must exist and a complete food
chain for increased biomagnification at each level (Figure 29). The food
chain in the canals above Alligator Alley may not be sufficiently complete
to accumulate mercury to concentrations above the predator protection
levels because of increased eutrophication.
Mercury Bioaccumulation
16
Figure 29. Bioaccumulation of mercury up the food chain from the water to wading birds and
the Florida panther.
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South Florida Ecosystem Assessment Report
HABITAT ALTERATION
One of the greatest human impacts in South Florida has been to the
natural habitat. Over 50% of the historic Everglades wetlands have been
drained. In addition to habitat loss, there has also been significant alteration
of the remaining habitat. Because of eutrophication, about 4% (over
77,000 acres) of the Everglades is now cattail marsh (Figure 30). At the
turn of the 20th century, less than 1% of the marsh area was cattails.
Wet Prairie (46%)
Cypress (5%)
Pond(1%)
Cattail (4%)
Sawgrass (44%)
Figure 30. Current distribution of marsh types
found in the South Florida Everglades.
Study results indicate that the Everglades marsh habitat (Figure 30)
consists of 90% sawgrass and wet prairie communities and 4% cattail. As
ecosystem restoration efforts proceed, such as phosphorus control or
modifications to hydropattern, these relative habitat percentages can be
monitored to assess the effectiveness of restoration efforts. Decreased
percentages of cattail marsh can indicate decreased nutrient loading and
decreased eutrophication. Changes in the percentages of different habitat
types can also indicate an increase or decrease in the spread of exotic
species, such as the melaleuca tree. There are other project habitat
indicators that also provide information on other restoration issues (e.g.,
percent dry area).
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South Florida Ecosystem Assessment Report
HYDROPATTERN MODIFICATION
The greatest change that has occurred in the Everglades ecosystem is
the change in surface water depth, distribution, and timing. The original
intent of the canals and levees was to "drain the swamp" so it could be
used for agricultural production and urban development. A comparison
of a model simulation of the natural marsh water depth during a dry
season for the study area is shown in contrast to the actual measured
water depths in the study area in April 995 (Figure 3 I). Changing water
depth also can significantly impact plants and animals. Wading birds, for
example, might not be able to forage because of increased depth while
some fish species lose habitat because depths are too shallow. The present
ponding 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.
LOWGITO&E,!
Figure 31. Comparison of current (left) vs. simulated natural marsh (right)
water depths for the study area.
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South Florida Ecosystem Assessment Report
ECOSYSTEM RESTORATION TOOLS
Multiple tools are required to resolve multiple interrelated
environmenta issues. A number of tools are being used as part of the
Everglades ecosystem restoration efforts, including mathematical models.
To investigate the mercury contamination problem, for example, US EPA
has two models that are currently available. The Marsh Screening Model
(Figure 32) is a large-scale Everglades ecosystem model with relatively
simple mercury cycling formulations that can be used to screen different
policy and/or management scenarios and evaluate their potential effects
on reducing mercury contamination. A second model, BASS, is a food
chain model that provides insight on how mercury is bioaccumulated
through the food chain. BASS provides insight into the potential effects of
mercury on critical food chains
within the Everglades ecosystem.
US EPA is also developing a
dynamic mercury-cycling model,
MERCS.
Other tools have been devel-
oped by other agencies and are
being used to address important
environmental issues, such as
hydropattern modification. The
South Florida Water Management
District, for example, has devel-
oped several hydrologic models
that are being used to evaluate
different management approaches
for restoring the natural hydrology
to the Everglades. One of these
models is called the Natural
System Model. The Natural
System Model provides estimates
of what the hydrology might have
been under various meteorological and climatic conditions before major
drainage efforts began (Figure 3 ). A second hydrologic model simulates
current conditions within the marsh ecosystem and provides a tool for
Flow
Figure 32. Schematic showing the marsh screening model network.
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South Florida Ecosystem Assessment Report
evaluating the effects of different flood
control and water supply management
options on marsh hydrology. By using both
models and comparing and contrasting
their output, managers can better assess
which management approaches offer
Figure 33. Waste incinerators are one of the °Ptimal restoration options.
sources of atmospheric mercury.
Other agencies also have developed tools that are being used in the
Everglades ecosystem for different issues, such as eutrophication,
atmospheric emissions, habitat alteration, and other problems. While
mathematical modeling is one technology that is being pursued, this is
not the only set of tools in the toolbox. Improved and innovative field
sampling techniques, more precise analytical procedures and use of remote
sensing and satellite imagery are being used to investigate these issues.
The US EPA, for example, conducted a major study to investigate mercury
emissions from municipal and medical waste incinerators (Figure 33) and
a coal-fired cement kiln. They are in the process of evaluating the fate and
transport of this mercury and its possible deposition over the marsh (Figure
34). The State of Florida, the Electric Power Research Institute, and the
US EPA established a deposition monitoring network to determine the
atmospheric mercury forms and potential deposition to the marsh
throughout South Florida. The USGS is conducting mercury
biogeochemical and bioaccumulation process studies. Modeling,
monitoring, and process studies are complementary tools for addressing
Everglades ecosystem issues. All of these tools and their information must
be integrated to develop man-
agement approaches that will not
only restore and protect the
Everglades but also satisfy the
different societal demands for
water supply, flood control,
agriculture, and urban devel-
opment.
I
Figure 34. Fate and transport of mercury emissions from
the source to the atmosphere and then deposited over the
marsh.
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South Florida Ecosystem Assessment Report
POLICY AND MANAGEMENT IMPLICATIONS
WATER QUALITY
Mercury
The current water tota mercury criterion for protection
of aquatic life is 2 parts per trillion (ppt). One hundred
percent of the Everglades marsh has total mercury
concentrations less than 12 ppt. This criterion, therefore,
is under-protective because wildlife effects have been
observed and 00% of the Everglades is under a human
health fish consumption advisory. In addition, the predator
protection criterion for mercury in prey species of 00
ppb proposed by the US Fish and Wildlife Service is
exceeded in over 65% of the marsh area. This indicates that alligators,
raccoons, otters, endangered wading birds, other fish-eating animals, the
Florida panther, and humans are at risk from mercury contamination.
Figure 35. Wet deposition of mercury during
storms is a major source of mercury to the
marsh.
The current chronic mercury aquatic life criterion is underprotective.
Mercury Load ings
South Florida Water Management District monitored total mercury
concentrations biweekly at the pumps located on the canals surrounding
the Everglades Agricultural Area. Atmospheric deposition monitoring data
were collected at seven locations throughout South Florida. The data
from these two monitoring programs were used to estimate the annual
total mercury loads to the Everglades ecosystem (Table 2). Atmospheric
deposition in precipitation (Figure 35)
contributed from 35 to 70 times the
mercury loading to the fresh water
Everglades compared to Everglades
Agricultural Area stormwater. It is not
known what proportion of this
atmospheric deposition is of natural
versus anthropogenic origin. Atmos-
pheric mercury source apportionment
studies are scheduled for the next 4 to
5 years.
Table 2
Comparison of Atmospheric vs.
Surface Water Mercury Loading
Year
1994
1995
Atmospheric
Deposition
(Ka/vrl
140
140
EAA Water
Discharge
(Ka/vrl
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South Florida Ecosystem Assessment Report
Figure 36. EAA stormwater discharge
contributes nutrients and mercury.
Phosphorus
The Phase interim phosphorus control target has been
established at a maximum of 50 ppb. However in 1995,
97% of the marsh had total phosphorus concentrations
less than 50 ppb. In addition, over 88% of the marsh had
total phosphorus concentrations less than 25 ppb or half
the Phase total phosphorus control target. Discharges
from the Stormwater Treatment Areas at 50 ppb will
continue to increase Everglades eutrophication (Figure 36).
Discharges from the Stormwater Treatment Areas at 50 ppb will continue
to cause Everglades eutrophication.
Phosphorus-Mercury Interactions
The increased phosphorus concentrations measured in the Refuge,
the Everglades Water Conservation Areas, and the Park are above natural
background concentrations and may aggravate the mercury problem by
increasing the biomass of the periphyton mats in which additional mercury
methylation might be occurring. Recent studies by the USGS have indicated
that periphyton mats and associated microbial communities might serve
as methylation sites for mercury. Because the historic Everglades were so
nutrient-poor, there is a clear relationship between increased phosphorus
and eutrophication, which can result in increased plant biomass, including
periphyton. The effects of increased phosphorus cascade through the
ecosystem affecting more than just plant biomass. When production
exceeds some critical threshold, organic matter can bind mercury, making
less mercury available for methylation. In addition, if oxygen
concentrations go to zero because of decaying organic matter, sulfide can
be released that also binds mercury. Process and food web studies are
required to further define the driving factors and associated environmental
conditions.
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South Florida Ecosystem Assessment Report
AIR QUALITY
Based on the deposition monitoring (Figure 37), emission studies,
and an emissions inventory, the average mercury emissions for South
Florida are about 3 times higher than the state average. In South
Florida, the mercury deposition from precipitation downwind of the
urban area is about 2 to 3 times the background level. The emission
source studies indicate that municipal and medical waste incinerators
are the major atmospheric mercury emission sources in South Florida.
The portion of deposited mercury that comes from local sources has
not been determined. However, additional studies to provide better
estimates of natural mercury releases to the atmosphere are in
progress.
Figure 37. Air depo-
sition monitoring towers
are located at 7 sites
throughout South Florida.
Incineration, not natural sources, is the primary source of atmospheric
mercury in South Florida.
Hydropattern
Modification
Eutrophication
Merc LJ ry
Cycling
Endangered
Species
Figure 38. Restoration issues are highly interde-
pendent and must be addressed together.
ASSESSING THE RISK
US EPA Region 4 is in the process of
conducting a comparative ecological risk
assessment to determine which of these
environmental problems place the
Everglades ecosystem at greatest risk. The
comparative assessment is critical because
none of the problems occurs independently
of the others (Figure 38). Hydropattern
modification is a primary driver of all the
problems, but hydropattern can be
influenced by habitat alteration. Both of these
problems influence eutrophication and
mercury contamination and cycling.
Eutrophication, through phosphorus
addition, is apparently contributing to the mercury problem, and all of
these problems influence wildlife and the increased distribution of nuisance
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South Florida Ecosystem Assessment Report
exotic species. Assessing the risk to the ecological resources from the
multiple environmental threats in South Florida requires a common
reference frame for estimating the extent and magnitude of both the threat
and the ecological effects. The US EPA Ecosystem Assessment Project is
the first and only study, because of its sampling design and probability
samples, to provide a common reference frame for multiple environmenta
threats and effects. The spatial patterns of soil depth, phosphorus, fish
mercury, and water depth, for example, represent the first such unbiased
snapshots of the condition of the South Florida Everglades ecosystem.
The consistent and comparable data from this study are critical for a
comparative ecological risk assessment. Continued monitoring through
time will permit these comparative risk estimates to be refined,
contributing to better management decisions. In addition, the Ecosystem
Restoration Task Force has identified restoration success indicators (Table
3). These indicators can be built into the monitoring program and can be
used to evaluate different management options for ecosystem restoration.
Table 3
Example Ecosystem Restoration Success Indicators
Problem
Hydropattern Modification
Habitat Alteration
Eutrophication
Mercury Contamination
Endangered Species
Success Indicators
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
The greatest threat to the Everglades ecosystem, however, is assuming
the problems facing the Everglades can be managed independently from
each other. These problems are often interdependent and must be
addressed using holistic, adaptive management approaches. This forms
the foundation for the comparative ecological assessment of the relative
risks from each of the environmenta problems.
Comparative ecological risk assessment is a critical element of adaptive
management for ecosystem restoration.
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South Florida Ecosystem Assessment Report
ON-GOING AND FUTURE STUDIES
US EPA Region 4 has completed one full cycle of canal and marsh
sampling and is in the process of analyzing the information. This information
will be used not only to answer the seven policy-relevant questions (page
7) identified for mercury, but also to answer similar questions related to
the other environmental problems threatening the Everglades ecosystem
(Figure 39). While this information provides a sound baseline for
preliminary answers to these questions, one of the wettest years on record
occurred during the field sampling effort. Additional monitoring is essential
to determine the variability in the baseline patterns from
season to season and the effect of this variability on future
management decisions. Additional monitoring will increase
our ability to make statements about subareas in the
Everglades ecosystem under different water management
regimes and will minimize the time required to detect
changes from adaptive management actions. Monitoring
and iterative comparative ecological risk assessments should
continue over the next 3 years as scientific understanding
of the interactions among these problems develops.
WARhlNI
SP-.IIM hii liiuiil h*
urt
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South Florida Ecosystem Assessment Report
The US EPA, a member of the South Florida Ecosystem Restoration
Task Force, is contributing to other studies being conducted as part of the
restoration effort. This project is contributing to on-going mercury
biogeochemistry and bioaccumulation process studies being conducted
by the USGS. For example, the Region 4 Ecosystem Assessment Project
has identified critical study areas in South Florida where process research
is needed to better understand the interrelationships among hydropattern
modifications, nutrient additions, and mercury cycling in the Everglades
ecosystems. This project is also providing complementary monitoring
information for simultaneous studies of atmospheric mercury emission,
transport, and deposition in South Florida. In addition, the US EPA is
working with the SFWMD Everglades Nutrient Removal Project and
Stormwater Treatment Area Studies, the US Army Corps of Engineers
Central and Southern Florida Project Re-study, and Florida Department
of Environmental Protection studies. The first comparative ecological risk
assessment, incorporating results from these efforts, is planned for late
997.
The US EPA Region 4 Ecosystem Assessment Project provides a critical
framework and foundation for assessing the effectiveness of Everglades
ecosystem restoration activities into the 21st century.
26
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PATTERNS OF OTHER CONSTITUENTS
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