EPA
United States
Environmental Protection
Agencv
Region 4 Science & Ecosystem
Support Division and Water
Management Division
EPA 904-R-07-001
August 2007
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The Everglades Ecosystem Assessment Program is being conducted by the United
States Environmental Protection Agency Region 4 Science and Ecosystem Support
Division, with the Region 4 Water Management Division cooperating. Many entities
have contributed to this Program, including the National Park Service, United States
Army Corps of Engineers, Florida Department of Environmental Protection, United
States Fish and Wildlife Service, Florida International University, University of
Georgia, Battelle Marine Sciences Laboratory, FTN Associates Incorporated, United
States Geological Survey, South Florida Water Management District, and Florida
Fish and Wldlife Conservation Commission. The Miccosukee Tribe of Indians of
Florida and the Seminole Tribe of Indians allowed sampling to take place on their
federal reservations within the Everglades.
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US Army Corps
of Engineers
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Research Center
Battelle
The Universit)' of
Georgia
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EPA904-R-07-001
August 2007
EVERGLADES
ECOSYSTEM
ASSESSMENT
Water Management and Quality,
Eutrophication,
Mercury Contamination,
Soils and Habitat
Monitoring for Adaptive Management
A R-EMAP Status Report
U.S. Environmental Protection Agency Region 4
Science and Ecosystem Support Division
Athens, Georgia
This document is available on the Internet for browsing or download at:
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Everglades R-EMAP is a program of the United States Environmental Protection Agency's
Region 4 Laboratory [the Science and Ecosystem Support Division (SESD) in Athens,
Georgia], with the Region 4 Water Management Division (WMD) cooperating. Everglades
R-EMAP is managed by Peter Kalla of SESD. Daniel Scheidt of WMD is the associate
manager.
This report should be cited as: Scheidt, D.J., and P.I. Kalla. 2007. Everglades ecosystem
assessment: water management and quality, eutrophication, mercury contamination,
soils and habitat: monitoring for adaptive management: a R-EMAP status report. USEPA
Region 4, Athens, GA. EPA 904-R-07-001. 98 pp.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
EXECUTIVE SUMMARY
The United States Environmental Protection Agency's Everglades Ecosystem Assessment
Program is a long-term research, monitoring and assessment effort. Its goal is to provide critical,
timely, scientific information needed for management decisions on the Everglades ecosystem
and its restoration. Since 1993, three phases of marsh sampling and one phase of canal
sampling have been conducted throughout the Everglades at over 1000 different locations. The
Program is unique to South Florida in that it combines several key aspects of scientific study: a
probability-based sampling design, which permits quantitative statements across space about
the condition of the ecosystem; a multi-media aspect; and extensive spatial coverage.
This Program:
• contributes to documenting the effectiveness of phosphorus and mercury control efforts;
• contributes to the joint federal-state Comprehensive Everglades Restoration Plan (CERP)
by quantifying conditions in three physiographic regions: Everglades ridge and slough;
marl prairie/rocky glades; and Big Cypress Swamp;
• provides information on four groups of Everglades restoration success indicators: surface
water, soil and sediment, vegetation, and fish;
• provides a baseline against which future conditions can be compared and the effectiveness
of restoration efforts can be gauged;
• assesses the effects and potential risks of multiple environmental stressors on the
Everglades ecosystem, such as water management, soil loss, water quality degradation,
habitat loss, and mercury contamination; and
• provides data with multiple applications - updating and calibrating surface water
management models; updating models that predict periphyton or vegetation changes in
response to phosphorus enrichment or phosphorus control; developing empirical models
in order to better understand interrelationships among mercury, sulfur, phosphorus, and
carbon; developing water quality standards to protect fish and wildlife.
This report summarizes the results for the Program's 2005 Phase III biogeochemical
sampling. This survey documented ecological condition forthe 2,063-square-mile freshwater
portion of the Everglades Protection Area. As with any assessment of the environment
at large, the long-term goal of the Everglades R-EMAP Program is to first describe, then
diagnose, and finally to predict the status of ecosystem conditions. The focus of this report is
the description of the study area as a whole. Future publications will include examination of
various parts of the system individually. Diagnosis and prediction will be the focus of future
Program publications.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
Key findings:
• Mercury contamination - very slight changes in water: Statistical analyses
of Program data indicate that there was a small decrease in the concentration of
methylmercury in surface water in the wet season in 2005 as compared to the wet
season in 1995. Conversely, there was a very slight increase in the concentration of
total mercury in surface water in the wet season in 2005 as compared to 1995. This
parameter had a median of 2.0 parts per trillion for the duration of the Program, well
below the Everglades' water quality criterion of 12 parts per trillion. Unfortunately,
attainment of the present criterion for surface water has not prevented bioaccumulation
to unacceptable levels in prey fish.
• Mercury contamination - declining in mosquitofish, but still elevated: The overall
mercury concentration in mosquitofish, a key prey fish for Everglades gamefish and
wading birds, dropped markedly from 1995-1996 to 1999 and from 1999 to 2005. This
phenomenon was observed during the wet season and the dry season. However, during
the 2005 wet season approximately 65% of the marsh exceeded 77 parts per billion,
a concentration USEPA has recommended in trophic level 3 fish as being protective
of top predators such as birds and mammals. The highest concentrations continue to
be observed in Water Conservation Area (WCA) 3 and Everglades National Park (the
Park), as was the case in 1995-1996. Over the entire study area fish mercury was
highly correlated with mercury in forms of periphyton, but not with mercury in surface
water.
• Mercury contamination - bioaccumulation varies greatly over space: The
bioaccumulation of mercury from the water column to mosquitofish varies spatially by
a factor of approximately 10 throughout the Everglades. The highest concentrations
of methylmercury and total mercury in surface water generally occur in WCA 2 and
parts of the Arthur R. Marshall Loxahatchee National Wildlife Refuge (the Refuge)
- areas that do not have high mercury in mosquitofish. An inhibitory mechanism may
explain the lack of bioaccumulation in these waters. Significant, negative correlation
coefficients were found between bioaccumulation and forms of carbon and sulfur.
The Program's sulfur, carbon, phosphorus and mercury data can be used to identify
conditions associated with hot spots of mercury in biota, and to corroborate process
studies designed to identify factors that enhance or inhibit mercury methylation and
bioaccumulation. In addition, Program food web assessments will be available for most
wet season sample sites, to shed additional light on bioaccumulation.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
• Pronounced water quality gradients: There are clear spatial gradients in surface
water phosphorus, sulfate, organic carbon, nitrogen, chloride and conductivity in the
Everglades marsh. These gradients are due to the relative contribution of rainwater,
stormwaterand groundwater. The highest concentrations typically occur during the wet
season in WCA2, due to its proximity to the Everglades Agricultural Area and stormwater
discharges. Concentrations progressively decrease downstream. Location, time of
year, and water management practices are important factors that affect water quality.
• Canals are a conduit for pollutant transport: The canal system, constructed to provide
flood control and watersupply, is also an effective conduit forthe transport of degraded
water into and through the Everglades marsh system. Water management affects water
quality. Downstream water quality would be improved if canals were eliminated or if
they were operated to maximize surface water sheetflow and the diluting influence of
rainfall and cleaner marsh water. Regardless, pollutants should be controlled at the
source prior to discharge into the Everglades.
• Phosphorus enrichment: There was a slight decline in surface water phosphorus
observed during the 2005 wet season sampling event as compared to 1995. During
the November 2005 sampling event approximately 27% of the Everglades marsh had
a surface water phosphorus concentration greater than 10 parts per billion. However,
during 2005 soil phosphorus exceeded 500 milligrams per kilogram (mg/kg), Florida's
definition of "impacted", in 24% of the Everglades, and it exceeded 400 mg/kg, CERP's
restoration goal, in 49% of the Everglades. These proportions are higherthan the 16%
and 34%, respectively, observed in 1995-1996.
• Sulfate enrichment: About 57% of the Everglades marsh had a surface water sulfate
concentration exceeding 1.0 parts per million (ppm), CERP's restoration goal. This
contrasts with 66% observed in 1995. During November2005 surface watersulfate was
about 90 ppm in WCA2, well above marsh background of < 1.0 ppm. Interior portions
of the Everglades distant from stormwater discharges from the Everglades Agricultural
Area had concentrations < 1.0 ppm, although elevated concentrations were still found
as far south as Shark Slough within the Park. The surface watersulfate concentration
in the Everglades overall during the wet season showed a slight decrease from 1995-
1996 to 2005.
• Soil loss in the public Everglades: The Program previously found that from 1946
to 1996, about one-half of the peat soil was lost from approximately 200,000 acres of
the public Everglades that had been subjected to drier conditions. No overall change
in soil depth was observed from 1996 to 2005. About 25% of the Everglades overall
has 1.0 feet or less of soil, as does 53% of the Park. Water management must be
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
improved to maintain the remaining marsh soils if the plant communities and wildlife
habitat of these wetlands are to be preserved. The northern portion of WCA 3 must
be rehydrated if further soil loss is to be prevented.
• Marsh habitat is a mosaic: Sawgrass marsh and wet prairie were the two dominant
plant communities in the Everglades, representing 58% and 32% of the sites sampled
in 2005. Water quantity and water quality must be managed properly to maintain these
important habitats. Cattail was present, but not necessarily dominant, at 19% of the
sites sampled in 2005, and was generally associated with elevated soil phosphorus
or proximity to canals.
• Periphyton is conspicuous: Well-formed calcareous periphyton mats, a defining
characteristic of the Everglades marsh complex where naturally hard water exists,
were found at 63% of the sample sites.
• Ecological condition varies by location and time: The condition of the Everglades
varied greatly with location. Rainfall-driven portions of the system that are distant
from the influence of canal water, such as the interior of the Refuge and the southwest
portion of WCA 3, were found to have good water quality and low soil phosphorus. The
interior of the Refuge tended to have good water quality and the lowest phosphorus
concentrations observed in peat soils. In contrast, northern WCA 3 had poorer water
quality, thinner soil due to water management practices, elevated soil phosphorus,
and extensive cattail encroachment. Water Conservation Area 2 had phosphorus
enrichment and cattail encroachment, along with high sulfate, organic carbon, nitrogen,
chloride and conductivity in surface water. Water depth at any given location varies
with season and year.
• Environmental threats are interrelated: Ecological stressors such as water
management, soil loss, water quality degradation, cattail expansion, and mercury
contamination are often interrelated. Efforts to manage water quantity and pollutants
such as phosphorus, mercury and sulfur should be integrated.
The Everglades R-EMAP Program has provided monitoring and assessment data for
measuring ecosystem health and the effectiveness of Everglades restoration activities
from the 1990s into the twenty-first century. As CERP restoration efforts and Everglades
phosphorus and mercury control efforts proceed, this probability-based sampling can
be repeated to document the condition of the Everglades and the effectiveness of these
actions.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
ABBREVIATIONS
cdf = cumulative distribution function
Cl = confidence interval
cm = centimeter
cc = cubic centimeter
cfs = cubic feet per second
g = grams
ppb = parts per billion (ug/L)
ppm = parts per million (mg/L) or (mg/kg)
ppt = part per trillion (ng/L)
mg/kg = milligrams per kilogram (ppm)
mg/L = milligrams per liter (ppm)
ng/g = nanograms per gram (ppb)
ng/L = nanogram per liter (ppt)
ug/cc = micrograms per cubic centimeter
ug/g = micrograms per gram (ppm)
ug/kg = microgram per kilogram (ppb)
umhos/cm = micromhos per centimeter
AA = Alligator Alley (Interstate 75)
BAF = Bioaccumulation Factor
BCNP = Big Cypress National Preserve
BMPs = Best Management Practices
CERP = Comprehensive Everglades Restoration Plan
EAA = Everglades Agricultural Area
ENP = Everglades National Park
EMAP = Environmental Monitoring and Assessment Program
EPA = Everglades Protection Area
FID = Florida International University
LNWR = Arthur R. Marshall Loxahatchee National Wildlife Refuge
MeHg = Methylmercury
OFW= Outstanding Florida Water
Park= Everglades National Park
Refuge = Arthur R. Marshall Loxahatchee National Wildlife Refuge
R-EMAP = Regional Environmental Monitoring and Assessment Program
SFWMD = South Florida Water Management District
STA = Stormwater Treatment Area
TP = Total Phosphorus
USEPA= United States Environmental Protection Agency
WCA = Everglades Water Conservation Area
WCA 2A = Water Conservation Area 2A
WCA 3A = Water Conservation Area 3A
WCA 3B = Water Conservation Area 3B
WCA 3N = Water Conservation Area 3A north of Alligator Alley
WCA 3S = Water Conservation Areas 3A and 3B south of Alligator Alley
WY = Water Year
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
ACKNOWLEDGEMENTS
PARTICIPANTS IN THE 2OO5 USEPA REGION 4
EVERGLADES ASSESSMENT PROGRAM
USEPA Region 4
Program Offices
Wafer Management Division
Richard Harvey
Drew Kendall
Fred McManus
Science & Ecosystem Support
Division
Phyllis Meyer
Mel Parsons
Maggie Pierce
Danny Adams
Tim Simpson
Bobby Lewis
Sara Taich
Linda George
Kevin Simmons
Mark Bean
Brian Striggow
Chris Decker
Stacey Box
Morris Flexner
Linda Watson
Charlie Appleby
Mike Birch
Denise Goddard
Jenny Scifres
Sandra Sims
Tony Carroll
Pam Betts
Debbie Colquitt
Linda Kidd
Mike Wasko
Don Morris
Bill Cosgrove
Bill Bokey
Mike Peyton
Air, Pesticides & Toxics
Management Division
AnneMarie Hoffman
South Florida Water
Management District
Larry Fink
Darren Rumbold
Ken Rutchey
USEPA - Office of
Research and Development
National Health and
Environmental Effects
Research Laboratory
Tony Olsen
Tom Kincaid
Jo Thompson
National Exposure Research
Laboratory
David Spidle
Florida International
University
Jenny Richards
Len Scinto
Joel Trexler
Evelyn Gaiser
Tom Philippi
Yong Cai
Guangliang Liu
Dan Childers
Joe Boyer
Pete Lorenzo
Christine Taylor
Ruth Justiniano
University of Georgia
Marguerite Madden
US Armv Corps of Engineers
Elmar Kurzbach
Kerry Luisi
US Geological Survey
Bill Orem
Florida Department of
Environmental Protection
Tom Atkeson
Tim Fitzpatrick
Don Axelrad
US Department of the
Interior -- Office of Aircraft
Services
Mike McFarlane
Sheri Phillips
Teri Marshall
ILS. Inc.
Jerry Ackerman
Mike Crowe
Jason Collum
Candace Halbrook
Don Fortson
Tammi Keaton
Jason Wells
Pavel Tercelich
Bill Simpson
Jim Chandler
Michael Keller
Myron Stephenson
Venkat Mudium
FrankAllen
Eddie Bonnell
Xiaoping Yin
Biscavne Helicopters. Inc.
Clarence Lewis
Mario Govea
Mauricio Faulin
Jose Parra
John Marks
Jim Thompson
Daryl Martin
Heliworks. Inc.
Wes Gager
Battelle Marine Science Lab
Brenda Lasorsa
FTN SAssociates. Ltd.
Kent Thornton
Institute for Regional
Conservation
Steve Woodmansee
Steve Hodges
Keith Bradley
US Department of the
Interior — Everglades
National Park
Mike Zimmerman
Bob Johnson
Bob Zepp
Funding for this study was provided by the United States Environmental Protection Agency (USEPA)
Region 4 South Florida Office, West Palm Beach; USEPA Office of Water; USEPA Office of Research
and Development; the United States Department of the Interior; the United States Army Corps of
Engineers, and the Florida Department of Environmental Protection.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
US EPA REGION 4
EVERGLADES ECOSYSTEM
PROGRAM
EXECUTIVE SUMMARY 1
ABBREVIATIONS 5
ACKNOWLEDGEMENTS 7
INTRODUCTION and PURPOSE 8
BACKGROUND 10
The Everglades 10
A Troubled River 11
THE COMPREHENSIVE EVERGLADES
RESTORATION PLAN 14
USEPA REGION 4 EVERGLADES ECOSYSTEM
ASSESSMENT PROGRAM 18
Program Design 18
Data Quality Assurance 22
Data Uses 22
SAMPLING DESIGN and DATAANALYSIS 26
WATER MANAGEMENT 30
WATER QUALITY 34
Conductivity 34
Chloride 37
Sulfate and Sulfide 39
Organic Carbon 46
pH 48
SOILS and SOIL SUBSIDENCE 50
NUTRIENT CONDITIONS 57
Background 57
Water Phosphorus 60
Soil Phosphorus 61
Nitrogen 65
MACROPHYTES and PERIPHYTON 67
Plant Communities 67
Periphyton 70
MERCURY CONTAMINATION 72
CONCLUSION 81
LITERATURE CITED 82
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
INTRODUCTION and PURPOSE
The United States Environmental Protection Agency (USEPA) Everglades Ecosystem
Assessment Program (the "Program") is a unique, long-term, research, monitoring, and
assessment effort. Its goal is to provide timely scientific information that is needed for
decisions on the restoration and management of the Everglades ecosystem. Since 1993,
one phase of canal sampling and three phases of marsh sampling have been conducted
throughout the Everglades at over 1000 different sampling locations. The purpose of this
report is to document conditions in the Everglades during 2005, the Program's third phase
of marsh sampling. This Program is unique to South Florida in that it combines several key
aspects of scientific study-
• probability-based sampling design, which permits quantitative statements across space
about ecosystem condition;
• multi-media scope; and
extensive spatial coverage.
FIGURE 1 . Numerous environmental issues threaten the Everglades "River of Grass," such as water
management, soil loss, water quality degradation, and habitat alteration. Two important features of Everglades
habitat are shown here- sawgrass (background) and wet prairie-slough including well-developed periphyton
(foreground).
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
GOAL: Provide timely ecological information that contributes to environmental
management decisions on Everglades protection and restoration.
The Everglades Ecosystem Assessment Program contributes to Everglades phosphorus
and mercury control efforts and the Comprehensive Everglades Restoration Plan by:
• quantifying pre-restoration conditions in the marsh during 1995, as well as conditions
subsequent to the initiation of restoration efforts later in the 1990s;
• assessing conditions in three physiographic regions: Everglades ridge and slough; marl
prairie/rocky glades; and Big Cypress Swamp;
• providing information on four groups of Everglades restoration success indicators: water, soil
and sediment, vegetation, and fish;
• providing a baseline against which future conditions can be compared, as well as change
detection to gauge the effectiveness of restoration efforts;
• assessing the effects and relative potential risks of multiple environmental stressors on the
Everglades ecosystem, such as water management, soil loss, water quality degradation and
nutrient enrichment, habitat loss, and mercury contamination;
• providing unbiased estimates of ecosystem health with known levels of uncertainty;
• permitting spatial analyses and identifying associations that provide insight into relationships
among environmental stressors and observed ecological responses; and
• providing data with multiple applications, such as updating and calibrating surface water
management models; updating models that predict periphyton or vegetation changes in response
to phosphorus enrichment or phosphorus control; developing empirical models in order to better
understand interrelationships among mercury, sulfur, carbon, and phosphorus; and developing
water quality standards to protect fish and wildlife.
USEPA Region 4 and the Florida International University Southeast Environmental
Research Center began this Program in 1993 to monitor the condition of the South Florida
ecosystem. This Program has been carried out in cooperation with the United States Army
Corps of Engineers, Miccosukee Tribe of Indians of Florida, Seminole Tribe of Indians, United
States Fish and Wildlife Service, National Park Service, United States Geological Survey,
Florida Department of Environmental Protection, Florida Fish and Wildlife Conservation
Commission, and the South Florida Water Management District.
This report, specified as a deliverable in the 2005 Phase III study plan, describes the
ecological condition of the Everglades as a whole during the intensive 2005 marsh sampling
effort. All reports and data for the Program are available on the internet at .
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 2. The Everglades wet prairie - sawgrass marsh mosaic.
BACKGROUND
THE EVERGLADES
"Here are no lofty peaks seeking the sky, no mighty glaciers or rushing streams wearing
away the uplifted land. Here is land, tranquil in its quiet beauty, serving not as a source
of water but as a last receiver of it."
"The Everglades were not really set aside for any kind of geological wonders or scenic
features. It's the first national park set aside simply for its wildlife and the plants and
trees - for its biological diversity."
President Harry Truman, Everglades National Park dedication, 1947.
The Florida Everglades is one of the largest freshwater marshes in the world.'1' The marsh
is a unique mosaic of sawgrass, wet prairies, sloughs, and tree islands. Just over 100 years
ago, this vast wilderness encompassed over 4,000 square miles, extending 100 miles from
the shores of Lake Okeechobee south to Florida Bay. The intermingling of temperate and
Caribbean flora created habitat for a variety of fauna, including Florida panthers, alligators,
and hundreds of thousands of wading birds. The Everglades of the past were defined by
several major characteristics:
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
How the water flowed. Water connected the system, from top to bottom. Surface water
flowed freely and slowly across the flat and level landscape. Rainfall during one season
was still available during another. The enormous amount of water storage capacity and
the slow flow made wetlands and coastal waters less vulnerable to South Florida's variable
and often intense rainfall.'2'
Vastness. The large area provided a variety of wildlife habitats. Millions of acres of
wetlands provided large feeding ranges and diverse habitat for wildlife. The vastness
produced abundant aquatic life while facilitating recovery from hurricanes, fires, and other
natural disturbances.'2'
Diverse mosaic of landscapes. The Everglades was a complex system of plant and
animal life dictated in part by varied water regime - minimum, average, and maximum
water depths, along with the duration of surface water inundation. This resulted in diverse,
expansive areas of wet prairies, sawgrass marshes, cypress swamps, mangrove swamps,
coastal lagoons and bays.'2'
Natural water quality conditions. There were no external sources of pollutants to the
ecosystem. There was no urban development or agriculture. Nutrients, ions, and metals
all occurred at natural concentrations. Rainfall recharged groundwater and generated
surface water, which interacted with the natural plant communities and soils. The slow
flow of surface water across the landscape provided ample opportunity for cleansing by
extensive wetlands. The sawgrass marshes and wet prairies
of the Everglades developed under conditions of extremely low
phosphorus concentration.
The mosaic of habitats, their vastness and the variety of water
patterns supported the long-term survival of wildlife under a range
of seasonal and annual water conditions.
A TROUBLED RIVER
One century ago, the greatest threat to wading bird populations
was hunting (Figure 3). During the last century, however, the
Everglades became a troubled system. In response to periods
of drought in the 1930s and 1940s, and severe flooding with loss
of human life in the 1920s and 1940s, the Central and Southern to the decimation of Everglades
,-, • , ,-, , ~ x , r, • x xx, r, • xx x ,• .. ~, „ , wading bird populations around
Florida Flood Control Project (the Project) was created in 1948 by 190o.
i i
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
federal legislation. The Project's often conflicting purposes
include flood control, water level control, water conservation,
prevention of salt water intrusion, and preservation offish and
wildlife. The Project became one of the world's most extensive
public water management systems, consisting of over 1,800
miles of levees and canals, 25 major pumping stations, and
over 200 large and 2,000 smaller water control structures.
When the Project was designed in the 1950s, about 500,000
people lived in the region, and it was estimated that there might
be two million people by 2000.'2' The Project has effectively
provided flood control and water supply to facilitate urban and
agricultural growth.
Today, 50% of historic Everglades wetlands have been
drained. The Everglades ecosystem has been altered by
extensive agricultural and urban development (Figures 4 to
8). South Florida's human population, which by 2000 was
eight million, continues to increase, encroaching on the natural
system and requiring increasing volumes of water. This human
population is projected to increase to 15 million within a few
decades.'2' (Figure 4).
The Everglades landscape changed dramatically during
the twentieth century as drainage canals were dug to facilitate
development. Most of the remaining Everglades are in
the Everglades Protection Area (EPA): Arthur R. Marshall
Loxahatchee National Wildlife Refuge (LNWR or the Refuge),
Everglades National Park (ENP or the Park), and the Water
Conservation Areas (WCAs) (Figure 8). Everglades National
Park, which was established in 1947, includes only one-fifth
of the original "River of Grass" that once spread over more
than 4,000 square miles (2 million acres).'4' One-fourth of the
historic Everglades is now in agricultural production within the
1,000-square mile Everglades Agricultural Area (EAA), where
sugar cane and vegetables are grown on the rich peat soils of
drained sawgrass marshes. Another one-fourth of the historic
Everglades has been drained and converted into urban areas
along Florida's lower east coast.
1900 1930
1960
2020 2050
FIGURE 4. South Florida population
in millions from 1900-2050 (projected).
Flood control provided by the Central and
Southern Florida Project has made urban
expansion possible12'31.
FIGURES. Urban expansion into
drained Everglades wetlands within western
Broward County, 1995. Note the black peat
soil.
BSBiBZsiC/'v ' ""iJrr-,- -rariiSKato*?!
FIGURE 6. Urban expansion into
Everglades wetlands in western Broward
County, 1995.
FIGURE 7. Residential development
on former Everglades wetlands in western
Dade County, 2005.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 8. Satellite image of South Florida, circa 1995, with the areas sampled outlined in yellow:
Everglades Agricultural Area (EAA); Arthur R. Marshall Loxahatchee National Wildlife Refuge (LNWR);
Everglades Water Conservation Area 2 (WCA 2); Everglades Water Conservation Area 3 north of Alligator
Alley (WCA3A N); Everglades Water Conservation Area 3 south of Alligator Alley (WCA3AS); the eastern
portion of Big Cypress National Preserve, and the freshwater portion of Everglades National Park (ENP).
Light areas on the east are urban development. The black line approximates the extent of the historic
(pre-1900) Everglades marsh. The Everglades watershed extends north of Lake Okeechobee.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
During the last century, the Everglades became subject to
multiple, often interrelated, environmental threats. Effective ecosystem
protection and restoration requires addressing these threats holistically.
Although one-third of the 16,000 square mile Everglades watershed is in public ownership,
there are many environmental issues, often interrelated, that must be resolved to protect
and restore the Everglades ecosystem. These include: water management complexities;
water supply conflicts; loss of water storage capacity; soil loss; water quality degradation
and eutrophication; mercury contamination of game fish, wading birds, and Florida panthers;
habitat alteration and loss; protection of endangered species; and introduction and spread
of nuisance exotic species of plants and animals.
THE COMPREHENSIVE EVERGLADES
RESTORATION PLAN (CERP)
The Central and Southern Florida Project has provided flood protection and water supply
for urban and agricultural lands, as intended. However, the Project has simultaneously
altered the Everglades, and indeed the entire south Florida ecosystem. Much of the
Everglades no longer receives the proper quality or quantity of water at the right place or
the right time. The remnant Everglades no longer exhibits the
water regimes, vast area, and mosaic of habitats that defined
the pre-drainage, natural ecosystem. Wildlife habitat has been
lost or changed, and the number of nesting wading birds (wood
stork, great egret, snowy egret, tricolored heron, and white ibis)
decreased markedly during the twentieth century.'5' (Figure 9).
Historically, most water slowly flowed across or soaked into the
region's vast wetlands. Today, over one-half of the region's
wetlands have been irreversibly drained. Gone also are the water
storage and water quality filtration functions that these wetlands
once provided. The canal system quickly drains water from
developed areas and the wetlands that remain. On average, a
billion gallons of fresh water are discharged to the coast each
year. Discharges into the Everglades marsh are frequently too
much ortoo little, and at the wrong time (Figure 10). Some areas
are too wet while other areas are too dry. Overland sheetflow is
interrupted by levees and canals that crisscross the Everglades
FIGURE 9. Everglades wad-
ing bird populations significantly
declined during the 1900s.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 1 O. Historic (left) Everglades water flow
patterns and present flow patterns (right)(adaptedrrom2'61-
FIGURE 11. An extensive system of
canals, levees, and water control structures
has modified Everglades water conditions and
provides a conduit for pollutant transport. The
S-9 pump station (foreground) discharges
untreated stormwater from an urban basin into
the Everglades (background).
and can provide a conduit for pollutant transport from urban and agricultural areas (Figures
11 and 24). Nutrient enrichment has become a threat to the Everglades.
As the human population continues to increase, urban and agricultural water shortages
are expected to become more frequent and severe. Conflicts for water between natural
resources, agriculture, industry, and a growing population will therefore intensify.
THE SOLUTION
Many of the problems with declining ecosystem health revolve around four interrelated
factors: water quantity, quality, timing, and distribution (Figure 12). Consequently, the major
goal of restoration is to deliver the right amount of water, that is clean enough, to the right
places and at the right time. Since water largely defined the natural system, it is expected
that the natural system will respond to improvements in water management (Figure 13).
The Water Resources Development Acts of 1992 and 1996 directed the U.S. Army
Corps of Engineers to review the Project and develop a comprehensive plan to restore and
preserve south Florida's natural ecosystem, while providing for other water-related needs
of the region, including urban and agricultural water supply and flood protection. The
result is the Comprehensive Everglades Restoration Plan (CERP, or the Plan, ), which was authorized by the United States Congress in the Water
Resources Development Act of 2000.
The development of the Plan was led by the Army Corps of Engineers and the South
Florida Water Management District and a team of more than 100 ecologists, hydrologists,
engineers and other professionals from over 30 federal, state, tribal, and local agencies. The
i s
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 1 2. The right quality,
quantity, timing, and distribution of water
are all critical to South Florida ecosystem
protection and restoration121.
FIGURE 1 3. The anticipated effect of the Comprehensive Ever-
glades Restoration Plan (CERP). Without the Plan (left) restoration
targets will not be met (red). With the Plan fully implemented (right)
restoration targets likely will be met (green). Yellow indicates uncer-
tainty in meeting restoration targets121.
Plan includes about 180,000 acres of surface water storage areas; about 36,000 acres of
man-made wetlands to treat urban or agricultural runoff; wastewater reuse; extensive aquifer
storage and recovery; water management operational changes; and structural changes to
improve how and when water is delivered to the Everglades, including removal of some of
the canals or levees that prevent natural overland sheet flow. The entire Plan is projected to
take over 30 years and cost over $11 billion to implement, with the cost split equally by Florida
and the federal government. If nothing is done, the health of the Everglades will continue to
decline, water quality will degrade further, some plant and animal populations will be stressed
further, water shortages for urban and agricultural users will become more frequent, and the
ability to protect people and their property from flooding will be compromised.(2'7) In 2004
the State of Florida announced an effort to speed up funding, design and construction of
eight key CERP projects. This $2 billion effort, AccelerS, is focused at regaining some of
the water storage capacity that was lost with wetland drainage by building water storage
reservoirs, restoring water quality with treatment wetlands, and restoring surface water
sheetflow and enhancing water management options.
Given the $11 billion investment in CERP, as well as phosphorus and mercury control
efforts, monitoring and assessment of results are important. Monitoring data are needed
to determine ecosystem condition, identify threats, and evaluate environmental restoration
efforts. As CERP is being implemented in a phased manner, system-wide information is
needed. Monitoring objectives include:
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
To evaluate restoration success, we must have reliable
pre-restoration and post-restoration information on ecosystem condition.
• Documenting status and trends;
• Determining baseline variability;
• Detecting responses to management actions;
• Improving the understanding of cause and effect relationships.
Accordingly, CERP has adopted an integrated monitoring and assessment plan that
includes key performance measures as indicators of ecosystem health. Performance
measures are indicators of conditions in components of the natural and human ecosystem
that have been determined to be characteristic of a healthy, restored system. Achieving
targets for a well-selected set of performance measures is expected to result in system-
wide sustainable restoration. CERP performance measures are used to predict system-
wide performance of alternative plans and to assess actual performance following
implementation.(8)
There are 24 CERP performance measures for the greater Everglades focused on
water conditions, waterquality, plants and wildlife. The Everglades Ecosystem Assessment
Program collects data that are relevant to over one-half of these performance measures.
Example Everglades Ecosystem Restoration Performance Measures.!8'
Water Management Reinstate system-wide natural hydropatterns and sheet flow
Habitat Alteration Increase spatial extent of habitat and wildlife corridors
Eutrophication water tota| phosphorus must be < 10 ppb and meet stricter OFW
requirements for Park and Refuge. Soil TP < 500 mgAg with 400 mg/
kg goal. Surface water total nitrogen < or = 1994-2004 baseline.
Mercury Contamination No statistically significant increase in levels of mercury in fish tissue
Sulfate Contamination Surface water sulfate 1 mg/Lorless
Conductivity No more than 25% increase above background, maintain low
conductivity in Refuge
Periphyton Increase aerial coverage of habitats that reflect Natural Systems Model
Soil Loss Restore natural soil formation processes and rates
1 7
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
USEPA REGION 4 EVERGLADES
ECOSYSTEM ASSESSMENT PROGRAM
PROGRAM DESIGN
The attention and funding devoted to Everglades ecosystem restoration are
unprecedented. Therefore, it is imperative that ecosystem health be assessed repeatedly
and comprehensively in a cost-effective, quantitative manner. Such an assessment identifies
resource restoration needs and allows one to determine the effectiveness of restoration
efforts. A major defining feature of the Everglades is its large spatial area. Hence, to monitor
restoration it is essential to accurately determine the proportion of the current Everglades
that is subject to various human impacts. This Program employs a scientifically rigorous
method of accomplishing this requirement using probability-based sampling.
This Program uses a statistical, probability-based sampling strategy to select sites for
sampling. This approach was initiated throughout the United States in the early 1990s by
the United States Environmental Protection Agency and is referred to as R-EMAP (Regional
Environmental Monitoring and Assessment Program). The Everglades R-EMAP effort began
in 1993 in the freshwater portion of the Everglades. The Program area extends from Lake
Okeechobee southward to the mangrove fringe on Florida Bay and from the ridge along
the urbanized eastern coast westward into Big Cypress National Preserve (Figure 8). The
distribution of the 199 canal sites and the 990 marsh sites sampled from 1993 to 2005 is
shown in Figure 14. The samples represent the ecological condition in over 750 miles of
canals and over 3,000 square miles of freshwater marsh.
This Program was the first in the Everglades to sample canals at randomly located
probability-based locations away from water control structures. Canals were sampled in
September 1993 and 1994, and May 1994 and 1995 (about 50 sites persampling cycle).<9'10'11'
Four marsh transects (44 stations) along phosphorus gradients downstream of water
discharge structures were sampled during April 1994. Marshes were sampled at random
locations in Phase I during the dry season (April 1995 and May 1996) and wet season
(September 1995 and 1996), at about 120 sites persampling cycle.(9) Big Cypress Swamp
was also sampled during Phase I. During Phase II the freshwater Everglades marsh was
sampled during May 1999 and September 1999 at another 119 sites per cycle.'12'13' Phase
III was conducted in May 2005 and November2005 atanother228 Everglades marsh sites.
As of 2005 the Program has sampled 990 distinct marsh locations and 199 canal locations
throughout the freshwater Everglades and Big Cypress.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 1 4. The 199 canal stations and 990 marsh stations sampled by the Program from 1993 to 2005.
19
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
During the 2005 Phase III sampling there were five Program components conducted at
the 228 marsh stations (Table 1):
• classified vegetation maps were generated for square-kilometer plots centered on
the station, based on aerial photography flown in 2000;
• aquatic food webs were assessed;
• periphyton community composition was determined;
• plant species frequency was recorded within quadrats along transects, along with
exotic species;
• multi-media biogeochemical sampling was conducted to understand water quality
and soil conditions. This report focuses on the biogeochemical sampling.
TABLE 1 . Program history showing Phases, media and indicators.
Phase
Year(s)
Distinguishing
characteristics:
Stations
1
1 995 & 1996
Baseline data.
Big Cypress included.
Canals included 1993-
95
480
II
1999
Plant study added.
Canals & Big Cypress
omitted.
238
III
2005
Change detection.
Food web studies
added.
Invasive plant survey
added.
228
Biogeochemical media
Surface water
Floe
Porewater
Soil
Periphyton
Mosquitofish
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Macrophytic plants
Qualitative habitat
categorization
Species frequency
Classified vegetation
mapping
Invasive plant survey
Yes
No
No
No
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
Community ecology
Periphyton assemblage
Mosquitofish food
habits
Macroinvertebrate
assemblage
Isotope studies
No
No
No
No
Yes
Yes
No
No
Yes
No
Yes
Yes
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
Because the Program involves sampling remote locations throughout an extensive area,
each biogeochemical marsh sampling event is performed by two or three teams using
helicopters equipped with floats. It takes about 9 days for the field teams to simultaneously
sample about 120 sites total while moving upstream from south to north.
The six media sampled at each site included surface water (Figure 15), marsh soil
(Figure 36), periphytonous algae and diatoms (Figures 1, 54 and 56), and prey fish (Figure
15). Pore water (interstitial water contained within wetland soil) and floe (flocculent material
found at the surface water-soil interface, Figure 15) were sampled beginning in 1999. All of
these media are important for elucidating the cycling of nutrients and mercury. The Program
does not have a minimum surface water sampling depth due to the importance of shallow
conditions in understanding cycling processes for mercury and nutrients.
FIGURE 1 5. Biogeochemical sampling included surface water (top left), floe and soil (top right), and
mosquitofish (bottom). The surface water sampling apparatus (top left) and soil coring device (top right) were
designed and constructed for the Program.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
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DATA QUALITY ASSURANCE
The biogeochemical portion of this Program comprises a multi-media effort in which six
marsh media (Table 1) are sampled concurrently and consistently throughout the entirety of
the freshwater Everglades. During the 2005 sampling, in-situ physico-chemical data were
documented at 228 sampling stations. Eight analytical labs were contracted to perform the
necessary variety and volume of nutrient, anion, mercury, physical and biochemical analyses
for samples collected at these stations. There were about 60 laboratory test methods
performed forthe various analytes among the media sampled (Appendix I). Analytes included
total mercury and methylmercury, and forms of phosphorus, nitrogen, sulfur, carbon, along
with enzymes and physical parameters. The Program defined data quality objectives to
assure that data would meet Program goals. An independently reviewed Quality Assurance
Program Plan was developed in accordance with USEPA protocol.'14'125) Data quality was
an integral part of the planning and execution of the 2005 effort, including the selection of
qualified analytical laboratories and the refinement of field sampling methods.
CERP has recognized the importance of data quality, resulting in the adoption of Quality
System Requirements. In Everglades R-EMAP, quality assurance is treated as an essential,
co-equal component of the work, from earliest efforts in Program planning, during field
sampling events and subsequent laboratory work, and through to final data review and
validation. One goal of this Program is to produce data of known and documented quality
that satisfy pre-defined uses and requirements. The Program has an independent quality
assurance officer who oversees all aspects of data quality. Data that potentially could be
used for regulatory purposes, such as phosphorus, sulfur, and mercury, were obtained
from analytical laboratories that are accredited by the National Environmental Laboratory
Accreditation Program.
During May 2005, 109 stations were sampled and about 1970 sample containers were
generated. In November 2005,119 stations were sampled, generating about 3110 sample
containers (Figure 17). During 2005 about 25,000 sample results were produced, 100%
of which were subjected to an independent quality assurance review. Only 2 individual
analytical results were rejected as not meeting Program data quality objectives. About 10%
of the Program budget was invested in data quality assurance.
DATA USES
This Program permits a holistic view of indicators of ecological condition throughout
the freshwater canal and marsh system. An indicator is a measurable characteristic of the
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
Probability-based sampling design is an assessment approach that
provides unbiased estimates of ecosystem condition with known confidence.
FIGURE 16. The probability-based sampling design FIGURE 1 7. Surface water and pore water samples
ensures that all habitats, such as dense cattail, are sampled. in tne cnain of custody lab at the end of a day's sampling.
Samples were distributed to eight analytical laboratories for
determination of mercury, nutrient, and ionic content.
environment, abiotic or biotic, that can provide information on the condition of ecological
resources. The Program's large-scale perspective is critical to understanding the impacts
of different factors (such as phosphorus, mercury and sulfur distributions throughout the
canals and marsh, habitat alteration, or hydropattern modification) on the entire system,
rather than at individual locations or in small areas. Looking only at isolated sites in any
given area and extrapolating to the larger system can give a misleading perspective. This
Program is unique to South Florida: its extensive spatial coverage and sampling intensity are
unprecedented, as is its multi-media approach. It is the only Program sampling throughout
the Everglades with a probability-based design which permits quantitative statements about
ecosystem condition.
A key advantage of this Program's probability-based statistical approach is that it allows
one to estimate across space, with known confidence and without bias, the current status
and extent of indicators forthe condition of ecological resources.'15'16' Indicators of pollutant
exposure and habitat condition can be used to identify associations between human-induced
stresses and ecological condition. This design has been reviewed by the National Academy
of Sciences, and USEPAhas applied it to lakes, rivers, streams, wetlands, estuaries, forests,
arid ecosystems and agro-ecosystems throughout the United States.'17'18'
During planning forthe 2005 phase of the Program, efforts were made to assure that
data collected would meet critical information needs of managers and scientists involved
with Everglades protection and restoration. Program managers met with Florida and Federal
managers and scientists involved with CERP and Everglades phosphorus and mercury
:
23
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
-A*
control efforts. Entities represented included Everglades National Park, Arthur R. Marshall
Loxahatchee National Wildlife Refuge, the U. S. Army Corps of Engineers, the South Florida
Water Management District and the Florida Department of Environmental Protection. In
addition, the 2005 Program study plan was subjected to an external scientific peer review
by each of these agencies and by the USEPA R-EMAP national program office.
Parameters measured for the Program at each site can be used to answer questions
about multiple issues including:
• Water management (e.g., water depth at all sites)
• Water quality and eutrophication (e.g., phosphorus concentrations in water and soil,
cattail distribution)
• Habitat alteration (e.g., wet prairie and sawgrass marsh distribution, presence of exotic
plant species)
• Mercury contamination (e.g., mercury in water, soil, algae, and prey fish)
Specific questions related to Everglades restoration goals that this Program answers
include:
• How much of the marsh or canal system has a total phosphorus concentration greater
than 50 parts per billion (ppb) in surface water, Florida's initial phosphorus control goal, or
10 ppb, the water quality criterion for the Everglades? Is it changing overtime?
• How much of the marsh has surface water sulfate concentrations that exceed 1 part
per million (ppm), the CERP performance measure for Everglades marsh restoration?
• How much of the marsh is dominated by sawgrass? Wet prairie? In what percent of
the Everglades is cattail present?
• How much of the marsh has a soil total phosphorus concentration that exceeds
500 milligrams per kilogram, Florida's definition of "impacted" for Everglades soils, or 400
milligrams per kilogram, the CERP restoration target?
• How much of the marsh still has the natural oligotrophic periphyton community?
• How much of the marsh area is dry, and where?
• How much of the marsh soil has been lost due to subsidence? Is the rate of this loss
changing overtime?
• How much of the marsh has prey fish with mercury levels that exceed 100 ppb, a level
that presents an unacceptable increased risk to top predators such as wading birds?
• What water quality conditions are associated with marsh zones of high mercury
bioaccumulation?
The South Florida Ecosystem Assessment Program provides such information system-
wide for the freshwater Everglades marsh. Data from this Program have been used by
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
scientists and managers from over 20 agencies or private interests for many purposes,
such as:
• Assessing drought-related ecological risk in the Everglades'19'
• Determining which portions of the Everglades are phosphorus-impacted according
to Florida's Everglades phosphorus criterion rule(20'21)'and determining which portions are
phosphorus-impaired as defined by the Clean Water Act for the Total Maximum Daily Load
(TMDL) program
• Understanding morphological response of macrophyte species to phosphorus'22'
• Understanding sulfur cycling, the distribution of surface water sulfate and the penetration
of water with high sulfate content into the Everglades marsh'23'24'
• Understanding the penetration of water with high ionic content into the marsh in the
Refuge and its potential impacts on periphyton communities'25'
• Documenting reference conditions and developing CERP performance measures for
soil phosphorus and surface water conductivity and sulfate'8'
• Documenting mercury conditions in water and biota and calculating the ecological risk
to Everglades top predators such as birds'24'26'27'28'
• Using nitrogen, carbon and sulfur isotope data to understand spatial variations in
aquatic food webs'29'
The long-term goal of the R-EMAP Program is to first describe the environmental status
of the ecosystem, then to diagnose the probable causes of observed impairments, and
finally to predict ecological responses of the system to management actions. Description
is accomplished by the measurements and interpretations presented here; diagnosis is
furthered by multivariate statistics that relate the measurements to each other; and prediction
is done by using those relationships to project present-day actions into future status. This
report focuses on the first goal and initiates the second. The third goal is the subject of
forthcoming journal publications. This report describes ecosystem status and change based
on two decades of intermittent sampling of the marsh. Conclusions about status are based
on analyses of the system as a whole. Findings about change should not be construed as
classical trend analysis, since the frequency of sampling is low. Experience in the EMAP
Program nationwide suggests that this limitation applies more to surface water, which can
be affected by weather events, than to soil or biota, which change less rapidly from time to
time.'126'127'128) These more conservative media permit change detection overthe long term.
Results about water constituents will be placed in context as they are presented.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
SAMPLING DESIGN AND
DATA ANALYSIS
PROBABILITY SAMPLES
In a probability sample, every unit of the population has a known chance of being selected
and the sample is drawn at random. In 2005 a stratified random design was used, wherein
sampling stations were located within each majorsub-area separately, to assure a sufficient
number of stations in the smaller sub-areas (the Refuge and WCA 2, as compared to WCA
3 orthe Park). Sufficiency was judged by the resulting adequacy of coverage, important for
providing information to meet certain data quality objectives of the survey. Every location in
each majorsub-area had an equal chance of being sampled. The sampling design was not
biased to favor one marsh type over another (e.g., avoiding tall, dense sawgrass because it
is an unpleasant habitat in which to work, sampling only next to a road because it is easier,
or selecting a particular location because it looks good or bad). Two major advantages
are obtained from probabilistic designs: the results represent the spatial distributions of
the parameters that were measured; and the results can be used to estimate, with known
confidence, the proportion of the area that was in any given condition. Estimates for the
entire study area were made possible by accounting for unequal sample size among sub-
areas. Estimates can also be made by sub-area, but were not computed for this report.
KRIGING
Kriging is a geostatistical method of generating contour maps from irregularly spaced
data. Since random sampling stations are spaced in such a manner, kriging is the natural
choice for spatial depiction of R-EMAP results. The contours are isopleths, lines of equal
estimated value of any measurement. Kriging algorithms interpolate between actual data
points, producing a grid of estimated values from which the contours are drawn. The krigs
in this report are true to the data - i.e., the data value at each sampling station matches the
color of the contour interval at that point. For this report krigs were made by estimating a
value for each node (intersection of lines) of the grid using the linear variogram model (no
nugget effect). A variogram is an expression of how quickly the actual values change over
space, on average, while taking into account the overall variability of the data set. The
underlying assumption of variograms is that, on average, values from points closer together
are more similar than those from points farther apart. Variograms are a function of direction,
to account for directionality of physical processes that underlay the data. In the case of
biogeochemistry in the Everglades, the process is often water flow.
The krigs in the report are only included to provide visual information for parameters with
clear spatial gradients. Conclusions in the report about extent of impacts and changes over
time are not drawn from the krigs, but rather from various statistical tests.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
Particularly during the dry season, there are physical barriers to sheetflow in the
Everglades, such as levees and roads. However, during the height of the wet season
(generally the time of wet-season R-EMAP sampling), the sub-areas of the Everglades
are hydrologically connected by surface water flowing freely through numerous structures.
This concept is suggested by Figures 24 and 40 in the report. During November 2005 all
structures were open and had been for some time. For example, L-67A/C/X was a conduit
from WCA 3 into the Park. Connections between some compartments are so extensive
that they are treated in some hydrological models as one unit. For example, the South
Florida Water Management Model, a model used to project water conditions throughout the
Everglades, disregards the presence of Alligator Alley. While wet season connectivity is
neither perfect nor complete, isolation of the sub-areas is neither perfect nor complete as well.
The real truth lies somewhere in between, and is dependent upon proximity to water control
structures. Dry-season surface water conditions are different, but only to a greater degree,
with porewater conditions probably more so. An additional consideration involves surface
water total mercury. This constituent is driven more by atmospheric deposition than by
water flow, largely negating the influence of physical barriers. The preceding considerations
are the basis for kriging the entire study area as one unit, following the approach used in
previous reports and by other investigators.
In validating krigs of large, complex systems like the Everglades, it is useful to look
for places where the algorithm appears to have produced results that are a long-distance
extrapolation across a barrier, rather than interpolation between connected points. Based
on this logic, some krigs were generated by sub-area for this report. There are others that
were affected somewhat by extrapolation, especially in areas near levees where there were
few sampling points, and most notably where extrapolation was up-gradient, as is the case
where a point in WCA 2 affected the contours in the Refuge. However, in these cases the
effects are minimal and very localized.
PEARSON CORRELATION COEFFICIENT
Correlation is a statistical tool for determining the strength of interdependence, or
association, between two variables. The Pearson r coefficient (Appendix III) is an indicator
of the linear proportionality of associated variables. If two variables are perfectly correlated
in a linear fashion, a change in one variable is always accompanied by a change of equal
magnitude in the other variable. The coefficient can be any number between - 1 and +
1. Positive values of r result from direct correlation, where one variable increases as the
other increases, whereas a negative r means inverse correlation (one decreasing as the
other increases). Coefficients near 0 indicate weak correlation. In the case of Everglades
R-EMAP, measurements vary over space (station to station) as well as time. Data from the
same cycle can be analyzed for correlation, because the measurements (or environmental
27
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
-A*
samples preserved for subsequent chemical analysis) were obtained from the same place
at the same time. In addition to coefficients themselves, the statistical significance of the
coefficients is reported. The significance (p) of a statistic is a measure of the reliability of
the sample data set as a representative of the entire population of possible data points.
The value of p is the chance that the true coefficient in the population isO, or in other words,
that instead of a strong or even a weak correlation, there is none at all. For this document,
correlation coefficients are reported in the text only if p<0.001: a level at which there is less
than a 1 in 1000 chance that the two variables are not associated.
CDFS AND AREA ESTIMATES OF EVERGLADES
CONTAMINATION
One way to portray survey statistics is to plot the cumulative distribution function (cdf)
of the data (Figure 31). All estimates of area by cdf curve in this re port were gene rated from
the original data, using algorithms in the R statistical package developed in part by EMAP
program statisticians at the USEPA Office of Research and Development Laboratory in
Corvallis, Oregon. Krigs were not used to estimate cdf curves. A cdf curve can be used to
estimate the proportion of the Everglades where a given analyte was found at a concentration
above or below any value of interest. This is a major strength of R-EMAP's probability-based
sample design. In this report the cdf curve is shown in bold. By reading up to the cdf from
any concentration of interest on the x-axis, and then across from the curve to the y-axis,
one can read the corresponding proportion directly on that axis. Bounding the cdf are two
lines representing the upper and lower 95% confidence limits, respectively, calculated using
the Horvitz-Thompson estimator. These limits show the confidence interval (Cl) around the
area estimate. This interval, expressed as percentage points above and below the estimate,
indicates the precision of the estimate: narrower intervals represent more precise estimates.
Estimates tend to become more precise as the number of samples increases. At the 95%
confidence level, there is a 1 in 20 chance that the true value for the study area was outside
the range defined by the confidence interval. The Cl for any estimate is read in the same
manner as the estimate itself. For example, in Figure 31, 57.3 ± 6.0% of the 2063 square
mile Everglades region sampled had a surface water sulfate concentration exceeding the
CERP restoration goal of 1.0 mg/L. A typical R-EMAP data quality objective is to produce
95% CIs that are no largerthan ± 10%. Previous experience in the national EMAP program
and in the earlier phases of Everglades R-EMAP showed that approximately 125 stations
was a sufficient sample size to meet this objective.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
STATISTICAL TESTING FOR DIFFERENCES ACROSS
SAMPLING YEARS
Any pair of R-EMAP data sets, represented by their respective cdf curves, can be tested
statistically to indicate a difference, or lack thereof, between them. The test statistics for cdf
curves used in this report (Wald, mean Eigenvalue, and Satterthwaite) express the likelihood
of differences or similarities between values obtained at neighboring sample sites. These
tests allow for statistical inference to the sampled population, or study area. In other words, if
curves from different time periods or sampling phases are different, the underlying condition
of the resource can be said to have changed. Statements about change are made with a
specified degree of confidence, typically no more than a 1 in 20 chance of being wrong.
This chance is expressed as a probability (p< 0.05 in the typical case). The source of such
an error is that the supposed difference is due merely to random differences between the
samples, instead of being a real change in the resource caused by some natural phenomenon
or human activity. Only a random sample spread out over an entire study area (R-EMAP)
can be used to draw conclusions about the whole area.
Z-TEST
To corroborate the results of the cdf tests, and to answerthe different question, "Are the
means (averages) of two R-EMAP data sets different enough to infer that there has been
an increase or decrease of the mean overtime in the study area?", another statistical test
was employed. It is a version of the commonly used test (t-test) for a difference between
the means of two populations represented by large, independent samples having unequal
size and variability. The version used for survey (probability) samples, the z-test, takes into
account the slightly unequal density of stations from sub-area to sub-area in the stratified
design of the 2005 survey.
BOX AND WHISKER PLOTS
A box-and-whisker plot (Figure 38) is another way to portray survey statistics for
measured variables. This type of graphic depicts the distribution, or general shape, of the
data for any variable of interest. The large box shows the interquartile range, between the
25th and 75th percentiles, which contains the middle half of all the data values. The whiskers
include values outside the interquartile range that are not considered outliers (larger or smaller
than the percentiles by at least 1.5 times the interquartile range) or extremes (2 times the
range). Half of all the values are greater than the median, and half are less.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
WATER MANAGEMENT
FIGURE 1 8. Rainfall at an Everglades wet prairie-slough in WCA 3 during the May 2005 field sampling.
Surface water depth is about 2 feet.
Adominant force defining the historic Everglades was water: highly seasonal rainfall; slow,
unimpeded, sheet-like surface flow; and a large storage capacity that prolonged wetland
flooding. These characteristics, along with subtle changes in ground surface elevation of
only a few feet over tens of miles, produced a variety of water depths and hydroperiods
(duration of surface water inundation). Water helped create the ridges and sloughs of the
landscape. It also affects the foraging success of nesting wading birds. Because changes
in surface water depth, distribution and hydroperiod caused many of the harmful changes
to the historic Everglades, water is key to ecosystem preservation and restoration. Rainfall
and the general patterns of water depth observed from 1995 to 2005 are described in this
section.
Rainfall is highly seasonal, with about 80% falling during the May to October wet season
(Figures 18 and 19). Rainfall during the 1995-1996,1999, and 2005 sampling periods varied.
Discharge through public water pumping stations is also highly seasonal. For example, at
S-8, a pumping station that provides flood control for part of the Everglades Agricultural Area,
monthly discharge varies from zero during the winter dry season to 68,000 cubic feet per
second (about 136,000 acre-feet) in response to summer and fall rain events (Figure 20).
so
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 1 9. Monthly rainfall (inches) from 1995 to 2005 at S-8, a pumping station that provides flood
control for part of the EAA by discharging water southward into the Everglades.
FIGURE 2O. Monthly discharge at S-8. Discharge varies from zero to several thousand cubic feet per
second in response to rain events.
Marsh water depths vary greatly with season, year and location in response to rainfall and
discharges from water control structures (Figures 18, 21 to 23). During all four wet season
sampling events the entire marsh was inundated. Water depths are deepest immediately
upstream of levees that impede the natural
flow of water, such as in the Refuge and
WCA 2 and WCA 3A (Figure 23). All of
these long-hydroperiod areas remained
wet during the study period, and unnaturally
deep water (depth of over five feet) was
observed within eastern WCA 3A where the
L-67 levee prevents sheetflow to the south.
Short-hydroperiod portions of the marsh are
FIGURE 21. The slough-wet prairie complex during
the dry season. subjected to annual periods of drying.
31
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
¥
1 !
FIGURE 22. Surface water depth encountered in the Everglades marsh from 1995 to 2005 at three loca-
tions. The eight Program biogeochemical sampling events are indicated by vertical red lines.
DRY SEASON
APRIL 1995
LtL
DRY
DRY SEASON
MAY 1996
Ltk
DRY
DRY SEASON
MAY 1999
DRY SEASON
MAY 2005
DRY
WET SEASON
SEPTEMBER 1995
WET SEASON
SEPTEMBER 1996
WET SEASON
SEPTEMBER 1399
WETSEASON
NOVEMBER 2005
FIGURE 23. Krigsof surface water depth encountered in the Everglades marsh during the eight Program
biogeochemical sampling events. Kriging is a statistical technique for drawing contour maps.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
The subtropical Everglades ecosystem is subjected
to varying climatic conditions, including hurricanes and
drought. R-EMAP marsh sampling events occurred
from 1995 to 2005, a period that encompassed very dry
conditions as well as several hurricanes. Water was deeper
than average in the Everglades during September 2005 and
R-EMAP sampling was delayed. On October 23, 2005 the
eye of hurricane Wilma passed over the southern edge of
the EAA. Wilma inflicted wind damage but moved quickly,
providing only 2 inches of rainfall on the Everglades.'132' R-
EMAP sampling began 16 days later on November 8.
R-EMAP sampling events have occurred under a variety
of water conditions (Figures 22-23). During the dry season
sampling events the dry proportion of the marsh was 7% in
April 1995, 16% in May 1996, 54% in May 1999 and 30%
in May 2005. These estimates of area are not based on
krigs but rather are calculated from the raw water depth
measurements using statistical algorithms. The deepest
conditions were encountered during 1995. This report
largely focuses on the wet season for drawing conclusions
about changes over space and time, for several reasons:
_. .. . major gated spillways that move water within
The entire study area was represented; sample sizes were the Everglades (adapted from SFWMD). Blue
larger; and there were minimal effects of differential evapo- areas indicate deeper water due to the ponding
of surface water at levees.
concentration of analytes in water. Program data have been
used to validate predictive models of hydroperiod. The extent and distribution of dried areas have
repercussions for Everglades ecology.'19'30'
FIGURE 24. Surface water flow vectors
during the wet season. Black arrows indicate
major water control structures that pump storm-
water into the Everglades. Red arrows indicate
S-5A
S-6
S-7
S-8
S-9
Total
1995
146.6
173.4
106.8
208.1
77.6
712.5
7996
25.4
38.4
11.2
30.2
44.8
150.0
1999
54.1
74.2
60.4
107.8
69.9
366.4
2005
50.4
77.6
98.9
116.8
29.1
372.8
TABLE 2. Surface water discharge at the five
major pumps discharging stormwater into the EPA.
Flows are in cumulative thousands of acre-feet
for the 60 days prior to each R-EMAP wet season
sampling event.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
WATER QUALITY
CONDUCTIVITY
The conductivity, or specific conductance, of a solution is a measure of its ability
to carry an electrical current. It varies with the number and types of ions in solution.
Pure water has a very low electrical conductance of a few hundredths of a micromho per
centimeter (umho/cm).(31) Conductivity is very useful for understanding the source of water
and its flow path. The water in the interior marsh of the Refuge is soft, slightly acidic, and
strongly influenced by rainfall. The limestone (calcium carbonate) substrate underlying
the Refuge is overlain by several feet of peat so surface water is not in contact with the
limestone. In contrast, the rest of the Everglades marsh has hard water with a neutral pH.
In the shorter hydroperiod portions of the Park there is little soil, so surface water is subject
to greater influence by the limestone substrate. Conductivity of water is closely related to its
hardness, because calcium, the major contributor to hardness in the Everglades, also aids
in conductance. Conductivity is of ecological interest in that it is a determinant of periphyton
community composition in the Everglades. Periphyton communities in the Refuge are
dominated by desmid and diatom species, while the extensive periphyton mats (Figures 1
and 56) in hard water portions of the Everglades are dominated by calcium-precipitating
cyanobacteria with a high calcium carbonate content.'25'
The Everglades has pronounced conductivity gradients due to the relative influence
of rainwater, groundwater, and stormwater inflows (Figure 25). Pronounced spatial and
seasonal patterns are evident. Precipitation in the Everglades has very low ionic content,
with median annual specific conductivity for 2005 of about 18 umhos/cm.(32) In contrast,
the conductivity of water discharged from the EAA during the wet season is about 50 times
higher (1,000 umhos/cm).(10) The public canals that provide flood control for the EAA cut
into the shallow aquifer, which is highly mineralized and begins at a depth below the ground
surface of only six to ten feet. Conductivities in this aquifer at a depth of 20 feet vary from
about 500 umhos/cm to several thousand umhos/cm. From the 1940s to the 1980s there
was an increase in the mineral content of the shallow aquifer due to the upward migration of
groundwater, a response to removal of surface water by pumping forflood control.'33' During
1997-2003 the median conductivity at 10 farm canals within the EAA ranged from 770 to
1670 umhos/cm, as compared to 600 umhos/cm for Lake Okeechobee. The highest values
within the EAA occur in the S-5A and S-6 basins.(34) During 1974 when water from the EAA
was pumped into Lake Okeechobee, surface water conductivity was about 1000 to 1400
umhos/cm in canals within the EAA, with a decreasing gradient with distance into the lake
such that conductivity decreased to about 500 to 800 umhos/cm toward the interior.'35'
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
Previous R-EMAP data indicated transport of high conductivity water in stormwater
via canals well into the Everglades marsh.(9'10) The highest conductivity observed in the
2005 wet season of over 1000 umhos/cm is within WCA 2 due to its proximity to the EAA
and the influence of canal water and groundwater. Lower wet season conductivity in the
western portions of WCA 3A (about 300 umhos/cm) and the interior of the Refuge (about
100 umhos/cm) indicate that generally these areas remain more influenced by rainfall. The
highest conductivity values measured in the Refuge, 150 to 600 umhos/cm, all occurred at
marsh stations in close proximity to the perimeter canal. During November 2005 median
conductivities at the four pumps that provide flood control for the EAA (S-5A, S-6, S-7 and
S-8) were 1482, 1406, 968 and 421 umhos/cm respectively, while the median conductivity
in the discharge from Stormwater Treatment Area (STA) 2 into the Everglades was 1482
umhos/cm. [STAs are discussed in the section on nutrients.] High conductivity water is
transported downstream in canals draining the EAA, and there is a progressive decrease
SURFACE WATER
CONDUCTIVITY
NOVEMBER 2005
SURFACE WATER
CONDUCTIVITY
MAY 2005
FIGURE 25. Surface water conductivity in marsh during the May 2005 dry season (left) and November
2005 wet season (right).
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
-A*
southward to the Park with dilution by rainfall and marsh water.'10' Marsh conductivity
increases in the dry season due to lessening dilution by rainwater, evapo-concentration as
the marsh dries out, and greater influence of canal discharges. Pronounced conductivity
gradients clearly indicate pathways of water flow throughout the canal-marsh system and
the extent to which the water management infrastructure and its operation influence water
quality. From 1959 to 1974, as inflow to the Park at Shark Slough changed over time from
being dominated by marsh sheetflow to canal discharge at the new S-12 structures, wet
season mean marsh conductivity rose from 270 to over 500 umhos/cm.(36'37) During 1978 to
1982, conductivity varied spatially such that at structure S-12A (Figure 24), a gated spillway
that discharges water into the Park, conductivity averaged 303 umhos/cm, as compared to
1184 umhos/cm at S-7.(38) November 2005 Program data indicate that marsh conductivity
is highly correlated with chloride and sulfate [Pearson correlation coefficients of 0.98 and
0.84, respectively (Appendix III)].
Florida's Class III water quality criterion for conductivity is that conductivity shall not
be increased 50% above background, or exceed 1275 umhos/cm, whichever is greater. On
an annual basis Florida consistently reports conductivity excursions that exceed the Class
III criterion for the WCA2A marsh, as well as for inflows to the Refuge and WCA2A.'39' The
Park and Refuge are also Outstanding Florida Waters, which further requires that the water
quality condition that existed in these waterbodies during the year priorto March 1,1979 must
be maintained. Background conductivity within the interior of the Refuge is approximately 100
umhos/cm. The value of periphyton communities as a food source is affected by conductivity,
in that increases in water ionic content can shift periphyton community structure.'25'40'131)
Highly mineral water penetrates into the Refuge periphery. During 2004-2005 the median
conductivity in the perimeter marsh was 329 umhos/cm, as compared to 118 umhos/cm at
interior marsh locations.'41' Penetration of highly mineral water at 10 to 20 times background
conditions into the Refuge marsh has been documented since the early 1970s,'42'43' when
concern about the impact of this mineralized water on Refuge biota such as periphyton
was also identified.'42'44' The Class III criterion of 1275 umhos/cm is not considered low
enough to assure that mineral-induced shifts in periphyton communities will not occur in the
Refuge. Recognizing this, CERP has adopted an Everglades protection and restoration
performance measure for conductivity of no more than a 25% increase above background
while taking into consideration natural seasonal and annual variation.'8' The expectation
for restoration is that soft, low conductivity surface water will be maintained in the Refuge,
while hard, higher conductivity water consistent with background will be maintained in the
rest of the Everglades. However, given the inevitable groundwater-surface water interaction
due to the very presence of canals, to some extent elevated surface water conductivity is
unavoidable.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
CHLORIDE
The concentration of chloride varies throughout the Everglades depending upon
the relative influence of rainwater, groundwater and stormwater. The Everglades does
not have a surface water criterion for chloride. Chloride is a useful indicator of a water's
source. Precipitation in the Everglades had a volume-weighted annual chloride concentration
of 1.0 mg/L for 2005.'32' During the November 2005 wet season sampling, the lowest
chloride concentrations of 16 mg/L to 18 mg/L were observed in the interior of the Refuge
and southwestern WCA 3 away from canal inflows, while the highest concentration of 260
mg/L was observed in WCA 2 (Figure 26). During November 2005 the median chloride
concentration at flood control pump S-6, which pumps water from the EAA into STA2, was
194 mg/L, while the median chloride concentration in the discharge from STA 2 into WCA 2
was 199 mg/L. Concentrations at S-7 and S-8 are lower.(SFWMDdata) These concentrations are
similarto those reported during 1974-1976:
177 mg/L at S-5A and 186 mg/L at S-6.<45>
During 2004-2005, the median chloride
concentration in the Refuge interior was
23 mg/L, with a higher concentration of 47
mg/L in the marsh near the perimeter due
to penetration of mineral water from the
surrounding canal.(41)
The chloride concentration in the
shallow aquifer within the EAA at a depth of
20 feet is reported at generally between 100
to 200 mg/L. The chloride concentration
within this shallow aquifer increased from
the 1940s to the 1980s due to the upward
migration of ground water in response to
pumping for flood control.'33' During 1999-
2003 the median chloride concentration at
10 farm canals within the EAA ranged from
72 to 174 mg/L.(34> From 1959 to 1974, as
inflow to the Park at Shark Slough changed
overtime from being dominated by marsh
sheetflow to canal discharge at the new S-
12 structures, canal chloride concentration
CHLORIDE
SURFACE WATER
NOVEMBER 2005
FIGURE 26. Surface water chloride concentration
(mg/L) during the Novermber 2005 wet season.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
Pronounced spatial gradients in surface water conductivity, sulfate and
chloride throughout the canal and marsh system vividly demonstrate that
the canal system is a conduit for transport of pollutants. This transport is
an unintended consequence of the flood control project.
rose from about 20 mg/L to about 60 mg/L.(46)
Chloride concentration in the STA 1 West outflow generally varied between 100
to 200 mg/L from 1994-1999. As expected there was no removal of this conservative
constituent by this wetland treatment system.!47' For Water Year 2006 (WY, May 1, 2005
to April 30, 2006), STA 1W, STA 2, STA 3/4, and STA 5 discharged dissolved chloride at
concentrations of 142 mg/L, 157 mg/L, 73 mg/L and 33 mg/L respectively, with no removal
by the STAs.<48>
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
SULFATE AND SULFIDE
Sulfur is an element that exists in several forms in water bodies. Sulfur generally
occurs in surface water in the oxidized state as sulfate, an ion that is common in nature.
It is a natural ingredient of rainfall, surface water and groundwater. The common reduced
form of sulfur is sulfide, which is associated with sulfate reduction by anaerobic bacteria.
Sulfur is also a secondary nutrient required for crops. Sulfur is of particular interest in the
Everglades for three reasons: sulfate and sulfide have been implicated as factors in mercury
methylation and subsequent bioaccumulation;'49'50'56' elevated sulfate has been shown to
mobilize phosphorus in water bodies;'51'54' and sulfide in elevated concentrations can be
toxic to plants'51'53' and animals. Because of these ecological concerns CERP has adopted
the following performance measure for surface water sulfate: maintain or reduce sulfate
concentration to 1 milligram per liter (mg/L) or less throughout the Everglades marsh.'8'
There are no numericwaterquality criteria forsulfate
orsulfide in the Everglades. Nationally, USEPAdoes
not have a recommended surface water criterion
for sulfate. For sulfide USEPA recommends a
surface water criterion of 0.002 mg/L for protection
of aquatic life,'55' while there are no water quality
criteria recommended for sulfide in pore water.
Florida has not adopted water quality criteria
for sulfate or sulfide. However, Florida has
designated the Park and Refuge as Outstanding
Florida Waters, requiring that the
water quality that
existed
FIGURE 27. Surface water sulfate in the marsh and canal system during the 1993-1996 R-EMAP wet
season sampling events. White dots indicate sulfate was below lab analytical detection limits, which varied from
0.5 to 5 mg/L, yellow bars indicate sulfate was detected by the lab at <50 mg/L, orange bars indicate sulfate is
50 to 100 mg/L, red bars indicate sulfate >100 mg/L. The median wet season concentration in southern Lake
Okeechobee during these years was 31 mg/L.
39
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
as of March 1979 be maintained. In addition, although there are no numeric sulfur criteria
forthe Everglades, Florida waterquality standards state that "Substances in concentrations
which injure, are chronicallytoxicto, orproduce adverse physiological or behavioral response
in humans, plants or animals - none shall be present."(123) The stimulation of mercury
(Hg) methylation by sulfate enrichment and subsequent Hg bioaccumulation to levels that
necessitate fish consumption advisories is relevant. Toxic or inhibitory effects of sulfide on
plants are also relevant.
Sulfate concentration varies throughout the Everglades depending upon proximity to
the EAA and the relative influence of rainwater, stormwater and groundwater. The annual
volume-weighted sulfate concentration in rainfall within the Park for 2005 is reported at
0.70 mg/L. It was lower, 0.54 mg/L, during the June to August months that accounted for
57% of the annual precipitation.'32' Annual mean and median sulfate in rainfall forthe three
Everglades locations sampled by SFWMD were all less than 1.0 mg/L for WY2005 (Figure
29). Interior portions of the Park, Refuge and WCA 3 that are most influenced by rainfall
had sulfate concentrations in surface water near analytical laboratory method detection
FIGURE 28. Surface water sulfate concentration (mg/L) in the Everglades marsh during the dry season
(top) and wet season (bottom) sampling events from 1995-2005.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
limits of about 0.1 mg/L during November 2005 (Figures 29 and 30). During November
2005 the median sulfate concentration was 0.2 mg/L at the 39 R-EMAP stations depicted
in Figure 30 as being <1 mg/L. Some marsh interior stations distant from canals within the
Park (P37 and P34) and Refuge (LOX9) had 2002-2006 median sulfate concentrations of
0.1 mg/L, the analytical detection limit (Figure 30). This indicates that at certain Everglades
locations the marsh background sulfate concentration may be even less than the analytical
detection limit of 0.1 mg/L.
In contrast, the highest marsh concentrations are at locations that are proximate to canals
or stormwater discharges from the EAA. The R-EMAP Program previously documented
pronounced marsh and canal surface water sulfate gradients and seasonality during
1993 to 1996 (Figure 27).(10) Figure 28 shows surface water sulfate concentration in the
marsh for each of the Program sampling events from 1995-2005. Surface water sulfate
concentration is shown in Figure 29 for about 170 distinct
locations sampled during November 2005 (about
120 marsh locations sampled by the
R-EMAP Program and 50
marsh or water
FIGURE 29. Above: Surface water
sulfate in the marsh during the November
2005 wet season. Right: Mean annual
WY2006 sulfate concentration at locations
sampled by SFWMD. White dots indicate
sulfate <1 mg/L, yellow bars indicate sulfate
is 1 to 50 mg/L, red bars indicate sulfate
>50 mg/L. EAA canals were not sampled
during 2005.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
management structure locations sampled by SFWMD). The highest sulfate concentrations
of over 100 mg/L were observed in canals within the EAA during the wet season and in
the Water Conservation Area 2A marsh. During the 60 days prior to the November 2005
Program sampling, the fourstructures that provide flood control forthe EAAdischarged about
343,500 acre-feet of water into the EPA. The wet season sulfate concentrations at these
structures closest in time to the R-EMAP sampling event are as follows: S-5A,131 mg/L; S-6,
136 mg/L; STA 2 outflow at G-355, 106 mg/L; S-7, 86 mg/L; S-8, 21 mg/L and S-9, 2 mg/L.
This compares to concentrations during 1974-1976 of 92 mg/L at S-5A, 32 mg/L at S-6, 39
mg/L at S-7 and 29 mg/L at S-8.(45) During 1997-2003 the mean sulfate concentration at 10
farm canals within the EAA ranged from 45 mg/L to 119 mg/L. The highest concentration
occured in the eastern EAA in the S-2/S-6 basin.(34) Sulfate concentrations in southern Lake
Okeechobee during November2005 were about 22 mg/L (Figure 29). Concentrations in the
Everglades progressively decrease to the south and west. These spatial patterns indicate
that the canal system delivers sulfate from the north into Everglades marshes. Penetration
SULFATE
SURFACE WATER
NOVEMBER 2005
SULFATE
SURFACE WATER
MAY 2005
FIGURE 3O. R-EMAP surface water sulfate concentration (mg/L) during May 2005 (left) and November
2005 (right). Three fixed stations with median annual sulfate < 0.1 mg/L are shown by white circles (right, data
from SFWMD).
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
of sulfate well into the Shark Slough marsh of the Park is evident (Figures 27-30).
The concentration of sulfate in Everglades groundwater has been reported by various
investigators. Sampling of the surficial aquifer underlying the EAA at about 20 locations in
1983-84 indicated sulfate concentrations of 25 mg/L to 580 mg/L at a groundwater depth
of 45 feet'33', about 20 feet below the depth that the major canals penetrate. The highest
concentrations were in the eastern EAA in the area of the S-2 /S-6 basins. A1976-77 study
of water quality in the EAA reported sulfate at 20 mg/L to 490 mg/L in shallow groundwater,
with mean concentrations of 153 mg/L below sugarcane and 199 mg/L below vegetables.
The mean surface water concentrations ranged from 40 mg/L to 459 mg/L.(124) In contrast,
the median groundwater concentration in 189 wells tapping the Biscayne Aquifer was
17 mg/L.(122) The Biscayne Aquifer is the shallow, unconfined, highly-permeable aquifer
underlaying the Everglades and southeast Florida.
Agricultural sulfur (S) has been applied to EAA soils for various purposes. The sulfur
content of EAA peat soils is considered adequate to supply some S requirements. However,
surface application of S has been recommended when soil pH is > 6.6 in order to increase
plant nutrient availability, with a recommended application rate of 500 pounds S per acre.'57'58'
A1976-77 study of water quality in the EAA reported S application of 10 pounds per acre to
sugarcane and 78 pounds per acre to vegetables.(124) EAA soils have been prone to copper
deficiency, which has been addressed by treatment with copper sulfate. Magnesium has
been commonly supplemented by use of fertilizer blends containing potassium-magnesium
sulfate.<59>
Using data collected from 1995-1999, other investigators analyzed sulfur concentrations
and isotopic ratios for rainwater, EAA groundwater, and EAA fertilizer, concluding that
excess sulfate in the Everglades originates from canals draining the EAA.(61) The sulfate
concentration and isotopic data appearto exclude rainwater and some ground water as major
contributors. Isotopic evidence implicates agricultural fertilizer as a major contributor to the
sulfate load. This fertilizer could be recent additions, legacy additions, orsome combination
of both. However, EAA groundwater and oxidation of agricultural soil may also contribute
sulfate.'61' It has been reported that, based on isotopic composition, groundwater is not a
major source of sulfate to surface water in WCA 2A.(62)
The wetland STAs constructed and managed to remove phosphorus remove varying
amounts of sulfate. STA 1W is reported to have exhibited moderate removal of sulfate
from 1994 to 1999 (Figure 42).(47) During WY2006, for the STAs the flow-weighted sulfate
inflow concentration, flow-weighted outflow concentration and percent removal were as
43
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
so
g 70
<
J= go
re
S 5O
o
£ 4O
o
at
a- 3O
2O
1O
O
Estimate of Marsh Area 1995
Lower 95% Confidence Interval 1995
Upper 95% Confidence Interval 1995
Estimate of Marsh Area 2OO5
Lower 95% Confidence Interval 2OO5
Upper 95% Confidence Interval 2OO5
3O 4O 5O 6O 7O
Surface Water Sulfate Concentration (mg/L)
FIGURE 3 1 . Wet season 1995 (red) and wet season 2005 (blue) marsh surface water sulfate cumulative
distribution function (cdf) with the upper 95% and lower 95% confidence interval for marsh area. .
follows: STA-1W73 mg/L, 69 mg/L, 5%; STA-2 103 mg/L, 76 mg/L, 26%; STA-3/4 53 mg/L,
43 mg/L, 19%; STA-5 7 mg/L, 4 mg/L, 43% and STA-6 15 mg/L, 5 mg/L and 67%. Sulfate
removal by the STAs is highly variable (5% to 67%) and appears to be a function of inflow
concentration. The highest STA inflow sulfate concentrations occured in the S-5A and S-6
basins (73 mg/L and 103 mg/L respectively).(48) The eastern EAA and the S-5A, S-2 and S-6
basins consistently have the highest concentrations of sulfate in groundwater and surface
water. Elevated sulfate has been shown to mobilize phosphorus in waterbodies.'51'54' If the
high sulfate within in the STAs mobilizes phosphorus, this would limit STA performance,
especially for STAs 2, 1W, and 3/4. This issue has not been fully evaluated.
Based on the cumulative distribution function (cdf) of R-EMAP data, during November
2005 the proportion of the Everglades marsh where sulfate exceeded the 1.0 mg/L
restoration goal was 57.3 ± 6.0% (Figure 31). This compares to 66.1 ± 7.0% during 1995.
Statistical testing for differences between these cdf curves confirm that these proportions
are significantly different. The average concentration was less in 2005 than in 1995 as
well. These differences cannot be explained by dilution since the lower concentrations
observed during the 2005 wet season occured in shallower water than in 1995 (Figure 23).
Stormwater is a possible explanation, as stormwater inflow to the EPA in the 60 days prior
to the 1995 wet season sampling was double the inflow during the 60 days prior to the 2005
wet season sampling (Table 2). These differences in sulfate concentration, though real (in
a statistical sense), are subtle. Further analyses, such as additional corroboration of the
R-EMAP data with records from fixed stations, and normalizing the data by water depth, are
planned. These analyses may clarify the effect of variation at multiple time scales that are
44
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
SULFIDE
POREWATER
MAY 2005
SULFIDE
POREWATER
NOVEMBER 2005
FIGURE 32. Sulfide concentration in pore water during May 2005 (left) and November 2005 (right).
shorter than the frequency of R-EMAP sampling. These same considerations are applicable
to other analytes in surface water.
Sulfide concentration in porewaterduring 2005 also indicated pronounced spatial gradients
(Figure 32). Under anaerobic conditions sulfide is formed from sulfate. Sulfur speciation
and isotopic composition of Everglades plant materials suggests that sulfate reduction is
occurring in the periphyton mat.'60' Background sulfide concentrations throughout portions
of the Everglades marsh remote from canal inflows are less than 0.14 mg/L. In contrast,
pore water sulfide exceeded 1 mg/L, and even 5 mg/L, at several locations in WCA2A. High
sulfide can inhibit mercury methylation'50'63', but it can also be toxic to macrophytes.'52' These
elevated concentrations in WCA2Aare consistent with those reported to inhibit the growth
ofsawgrass.'24' The area of maximum sulfide concentration in porewater coincides with the
area of maximum sulfate concentration in surface water (Figures 30 and 32). Porewater
sulfide was correlated with sulfate in surface water and porewater, and with mercury in
surface water, periphyton and sediment (p<0.001) [Appendix III]. Porewater sulfide was
negatively correlated with mercury bioaccumulation (p<0.001).
45
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
ORGANIC CARBON
Organic matter is important for various biological and chemical processes. Carbon can
influence the availability of nutrients and serve as a substrate for microbial reactions.
Carbon is abundant in the Everglades because of the extensive peat soils that are as
much as 90% organic matter (Figures 36, 38 and 39). During 1993 to 1996 the Program
previously documented distinct spatial gradients in surface water organic carbon in
canals and in the marsh, with the highest concentrations observed in canals within the
EAA.(10) The origin of this carbon is most likely the peat soils of the EAA, with export in
stormwater due to flood control pumping. During 1974 when water from the EAA was
pumped into Lake Okeechobee, surface water Total Organic Carbon (TOC) was about 90
to 106 mg/L in canals within the EAA, with a decreasing gradient with distance into the
lake such that TOC decreased to about 20 to 50 mg/L toward the interior.(35)
DISSOLVED ORGANIC CARBON
SURFACE WATER
MAY 2005
1O
DISSOLVED ORGANIC CARBON
SURFACE WATER
NOVEMBER 2005
FIGURE 33. Surface water dissolved organic carbon during May 2005 (left) and November 2005 (right).
46
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
f
During 2005, Program data show that Dissolved Organic Carbon (DOC) in the Everglades
exhibited a spatial gradient and high seasonality with higher values found during the dry
season (Figure 33). The lowest DOC concentrations of 4 mg/Lto 10 mg/Lwere all found
during the wet season within the portions of the Park where marl soils of low organic content
occur. From 1994 to 1999 STA-1W exhibited no net removal of carbon, with about 93% of
the surface water TOC in the dissolved fraction.'47'
Carbon is of interest in that it plays a role in mercury cycling. Dissolved organic
matter binds mercury, affects mercury solubility and can influence mercury availability to
microbes that methylate mercury.
Areas strongly influenced by EAA
stormwater have higher dissolved
organic matter concentrations and
are more reactive with mercury
than more pristine areas of the
Everglades.'64' During the November
2005 Program sampling, DOC had
a significant negative correlation
with mercury bioacculation factor
FIGURE 34. Surface water samples collected during Phase
[Pearson correlation coefficient Of | canal sampling. Samples with more color were collected at
-065 P<0 001 (Appendix lll)l locations within or near the EAA. Samples with more color had
higher carbon content.
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
PH
The logarithm of the reciprocal of the concentration of free hydrogen ions
is refered to as pH. The pH of pure water is 7.00, or neutral. Increased hydrogen
ion activity lowers the pH toward acidity, while decreased activity increases the pH
toward becoming basic. The pH of unpolluted water is usually between 6.5 and 8.5.(31)
Rainwater in the Everglades had a precipitation-weighted mean pH of 5.0 for2005.(32)
In-situ surface water pH and soil pH varied spatially during November 2005, in
similar fashion (Figure 35). The soft-water Refuge has low capacity to buffer against acidity
(annual median alkalinities at interior locations as low as 8 mg as calcium carbonate per liter),
while the hard waters of the Park have high buffering capacity (annual median alkalinities
of about 200 mg as calcium carbonate per liter).'39' The marl soil found throughout much
of the Park (Figures 36 and 39) contributes to this buffering capacity and results in higher
pH
SURFACE WATER
NOVEMBER 2005
PH
SOIL
NOVEMBER 2005
FIGURE 35. In-situ surface water pH (right) and in-situ soil pH (left) during November 2005.
48
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
pH values. The lowest surface water pH of 5.66 measured for the Program from 1995-
2005 was encountered in the Refuge during the morning, and the highest pH of 8.39 was
encountered in the the Park during the morning. Surface water dissolved oxygen throughout
the marsh varied from 0.3 to 13.6 mg/L. In-situ soil pH exhibited a spatial pattern with the
lowest pH within the interior portion of the Refuge with highly organic soils and the highest
pH generally within the marl soils of the Park.
Photosynthesis by aquatic organisms removes carbon dioxide from the water
column during daylight hours, resulting in an increase in surface water pH.'31'42' In a natural
wet prairie community in the Park, with bladderwort and an extensive calcareous periphyton
mat, the pH atone location was shown to fluctuate over 24 hours from 7.1 at midnight to 8.5
late in the afternoon.'65' Given that during November 2005 measurements of in-situ water
pH for the Program occurred between 0800 and 1700 hours, and Program sampling took
place from south to north over a ten day period, the observed spatial pattern in pH cannot
be explained by diurnal fluctations.
The Everglades has a water quality criterion for pH of not <6.0 or >8.5. The Program
includes 15 of 736 pH measurements that were less than 6.0. All were in the interior of the
Refuge. Florida has routinely reported violations of the pH criterion within the most interior
portion Refuge where values lower than 6.0 are found, but these excursions below the
criterion are viewed as a consequence of the Refuge's naturally low alkalinity and are not
of ecological concern.'39'
49
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
SOILS and SOIL SUBSIDENCE
Soil is a key defining characteristic of an ecosystem, and soil preservation is an important
aspect of ecosystem protection. The Comprehensive Everglades Restoration Plan has
adopted objectives, performance measures, and performance targets in order to define
restoration goals, track ecosystem status, and measure restoration effectiveness. Among
these is restoring the natural rates of organic soil and marl soil accretion, and stopping soil
subsidence.'8'
There are two major soil types in the Everglades. The wetland soils of the central
Everglades are primarily peat (Figures 5 and 36) formed by slowly decaying plant matter.
The other major soil type found within Everglades wetlands
is calcitic mud or marl (Figure 36) commonly found in the
shallower peripheral marshes of the Everglades that are
subjected to shorter periods of surface water inundation.
Marl is found in association with thick, calcitic algal mats
(periphyton) (Figure 36), which precipitate calcium carbonate
from the water column.(66)
The Everglades are reported to have contained the largest
single body of organic soils in the world, covering over 3,000
square miles and accumulating to a thickness of up to 17 feet
in what is now the EAA.(67) The origin and perpetuation of
peat and marl soils are greatly dependent upon water depth,
the duration of surface water inundation, and the resulting
wetland vegetative communities. Diminished surface water
inundation can cause soil loss or changes in soil composition,
which may in turn result in altered vegetative communities.
These altered plant communities may cause further changes
in soil type and thickness as this different plant community
eventually decomposes and forms altered soil. Some soil
cores collected for the Program have alternating peat and
marl layers within the 0-10 cm profile.
Peat soils are subject to subsidence and loss of surface
elevation when drained. Oxidation, burning and compaction
are considered the dominant subsidence forces, and from a
practical standpoint are irreversible. An inch of Everglades
FIGURE 36. Everglades peat (top) and peat that takes a century to form can be lost within a few
marl (bottom). Bottom photo also shows a
benthic periphyton mat overlaying the soil years, or within a few hours if dry soils are subjected to fire.
so
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
From the 1940s to the 1990s, over one-half of the soil was lost from portions of
the Everglades. Water management must continue to improve in order to maintain
marsh soils and the plant communities and wildlife habitat of these wetlands.
Early in the twentieth century the deep peat soils (mostly formed by decaying sawgrass)
of the 700,000 acre EAAwere drained to facilitate agricultural production. The process of
soil formation was reversed in 1906 when the first canals were cut from Lake Okeechobee
through the EAA to the coast.'68' Subsequent subsidence within the EAA and efforts to control
it on agricultural lands are well documented. In 1912 much of the EAA had soils thicker
than 10 feet.'67'68' By 1988 only 17% of the EAA had soil thicker than 51 inches, while 53%
of the area had soils less than 36 inches thick, and 11% had soils less than 20 inches thick.
By 2050, under current agricultural practices, about 93% of the EAA is projected to have
soils less than 36 inches thick and about 53% is projected to have soil less than 8 inches
thick.'121' Based on these soil thickness projections, the decrease in soil volume within
the EAA from 1988 to 2050 is calculated to be 57% or 11.7 x 108 m3. The fate of certain
constituents of this soil, such as phosphorus, sulfur and mercury, are of potential concern
for the downstream Everglades.
Within the EAA, production of agricultural crops such as vegetables and the more prevalent
varieties of sugarcane require that the water table be maintained below the ground surface.
The ground surface of the EAA basin, which historically was sawgrass marsh that flooded
much of the year, is now several feet below that of circa 1910 due to subsidence. Frequent
rain events during the wet season necessitate repeated pumping in order to maintain the
water table below the ground surface, which continues to subside further. Each of these
flood control pumping events has the potential to leach and export soil constituents, such
as phosphorus, nitrogen, sulfur and carbon, in the stormwater pumped southward to the
Everglades. Agricultural Best Management Practices are directed at phosphorus removal.
The STAs are more effective at removing phosphorus than nitrogen, sulfuror carbon. Given
the projection, if realized, that one-half of the EAA may have less than 8 inches of soil by
2050, the viability of agriculture with current practices comes into question.'121' If residential
land use requires that the water table be maintained at even lower levels, conversion from
agriculture to residential land use could result in the need to export greater volumes of
stormwater to the Everglades.
Soil loss in the Everglades was largely due to water management practices during the
1900s. The major canals draining the EAA extend southeast through the Everglades to
the Atlantic Ocean and were completed by 1917. However, unimpeded surface water flow
from the EAA southward through the Everglades to the Park, Florida Bay, and the Gulf
of Mexico still occurred until the late 1950s, when levees were constructed forming the
southern boundary of the EAA. During the early 1960s additional levees were completed
that compartmentalized the Everglades into the Water Conservation Areas. By the 1960s
51
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
SOIL THICKNESS
FIGURE 37. Soil thickness measured at 867 locations during R-EMAP Phases I, II and III from 1995-2005.
The inset shows soil thickness as reported in 1946.(70)
52
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
n
— '
^
. ._. ^ ._.
0
Soil th
3
icknes*
'
<
§
D
> (feet)
^
•
n
a Mejdian
Zl 25%-75%
"T" Non-Outlier R
o Outliers
x Extremes
*
£
6 *"
T~ 3
j i
^T
_L r*~i
ange
Refuge WCA3N S. Slough
WCA2 WCA3S Park
Refuge WCA3N S. Slough
WCA2 WCA3S Park
b ilVledian
1 1 25%.75%
1 Non-outlier Range
0 Outliers
-K Extremes
Soil bulk density —
(g/cc)
i
1
*
j
I
L
*
— i
•f.
§
i".
— |—
1
+
J
j
i
i —
:
Refuge WCA2 WCA 3N WCA 3S S. Slough Park
FIGURE 38. Soil thickness (top), percent organic matter (middle) and
bulk density (bottom) by Everglades sub-area for soil cores at 0-10 cm.
Everglades surface water depths,
flow, and inundation periods had
been greatly altered.'691
The R-EMAP Program was the
first to consistently document soil
thickness, bulk density and organic
matter throughout the Everglades
system. The Program previously
documented soil subsidence in the
public Everglades.'10' Comparisons
of Everglades soil thicknesses
measured in 1995-1996 to those
reported by Davis in 1946'70) indicated
that short hydroperiod portions of
the Everglades such as WCA3 north
of Alligator Alley (Figures 40 and 41)
lost 39% to 65% (2.0 to 6.0 x 108 m3)
of its soil. Soil thicknesses of 3 to 5
feet in the 1940s had diminished to
only 1 to 3 feet by 1995-1996, with
less than 1 foot remaining in some
areas. WCA 3B and the Northeast
Shark Slough portion of the Park
were found to have lost up to 3 feet
of soil, representing a 42% and 53%
loss of volume, respectively. These
three portions of the Everglades,
about 200,000 acres, have been
subjected to decreased surface
water inundation since completion
of the Water Conservation Areas
about 50 years ago (Figures 23
and 40). It has been established
that from the 1940s to 1990s the
entire Everglades Protection Area
lost up to 28% of its soil volume
due to oxidation and subsidence.'101
53
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
ORGANIC MATTER
SOIL
BULK DENSITY
SOIL
FIGURE 39. Soil percent organic matter (left) and bulk density (right) for soil cores at 0-10 cm.
The R-EMAP Program continues to be the only source of soil thickness data throughout
the Everglades post-1940s.
Krigs of soil thickness measured for the Program in 1995-1996,1999 and 2005 suggest
no discernable difference among sampling events. Soil thickness data for 1995-2005 at
867 sampling sites are shown in Figure 37. The deepest soils are the peat deposits within
the Refuge, with a median soil thickness of 8.7 feet (Figure 38). Median soil thicknesses for
remaining portions of the study area were 4.1 feet in WCA 2, 1.5 feet in WCA 3A north of
Alligator Alley, 2.9 feet in WCA 3 south of Alligator Alley, 0.82 feet in the Park excluding Shark
Slough, and 1.7 feet in the longer hydroperiod portion of Shark Slough (SS) within the Park.
The overall median soil thickness for the Everglades is 2.3 feet. As of 2005 the volume of
soil in the freshwater Everglades study area was 4.0 x 109 m3. About 25.1 ± 2.0% of the
Everglades had a soil thickness less than one foot, while 36.1 ± 2.1% had a soil thickness
of over three feet. The deepest peat in the Everglades outside of the Refuge is in those
portions of WCA 2 and southern WCA 3 which typically stay inundated year-round. Most of
the Park has a soil thickness of less than 1 foot, as does a portion of northern WCA 3.
Soil organic matter observed during 1995 to 2005 at 862 sites ranged from <1% to
54
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
100% (Figures 38 and 39), with a median of 80%. Peat soils are highly organic, while
marl soils are primarily mineral. The highest organic matter content was found in the thick
peat soils of the Refuge, having a median of 94%. WCA 2A and WCA 3 south of Alligator
Alley also had soils exceeding 75% organic matter. These highly organic zones coincide
with the longer hydroperiod portions of the system. The area of maximum soil loss within
WCA 3 north of Alligator Alley had a median soil organic matter content of 63%, the lowest
in the Water Conservation Areas. The peat soils in the Shark Slough trough of the Park
had a median organic matter of 83%, in contrast to the marl soils of the Park which have a
median of only 27%.
Soil bulk density, the mass of dry soil per unit of bulk volume, ranged from 0.04 to 1.30 g/cc
(Figures 38 and 39). The highly organic peat soils of the Refuge had the lowest bulk density,
with a median of 0.06 g/cc, in contrast to the marl soils of the Park which had a median of
0.36 g/cc. The median soil bulk density for WCA 3 north of Alligator Alley (Figure 41) was
0.17 g/cc, the highest in the Water Conservation Areas. Within the Water Conservation
Areas, this portion of northern WCA 3 had the lowest organic matter content, the highest
FIGURE 4O. Average annual number of days of surface water innundation 1965-1995 (right) and overland
flow vectors (left). Figures are from South Florida Water Management District. Note the diminished flow and
drying in northern WCA 3A. This drier portion of the Everglades is susceptible to soil oxidation and fire.
55
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 41 . Interstate 75 (Alligator Alley) at the eastern edge of the Everglades looking westward.
Northern WCA 3A is to the right.
bulk density, and the greatest soil loss. All of these observations are suggestive of formerly
deeper peat soils being subjected to drier conditions due to water management changes
overthe last 60 years. Surface water inundation has been reduced, and consequently soils
have subsided and become less organic (Figures 37-40), due to increased biochemical
oxidation and more frequent wildfires.
56
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
NUTRIENT CONDITIONS
BACKGROUND
Interior Everglades marshes removed from anthropogenic nutrient sources have extremely
low total phosphorus (TP) concentrations in surface water. For WY2005 (May 1, 2004 to
April 30, 2005) annual median TP concentrations at fixed stations within the Park were as
low as the method detection limit of 2 parts per billion (ppb).(71) Historically, the Everglades
ecosystem was very nutrient poor, with surface water phosphorus concentrations less than
10 ppb.'72'119) Rainfall was the dominant source of external phosphorus, and the hydrology of
the marsh was rainfall-driven, with slow overland sheet flow supplying waterto downstream
wetlands. There were no canals in the Everglades region prior to the early part of the
twentieth century. This naturally nutrient-poor condition resulted in a unique mosaic of
habitats, such as wet prairies, sloughs, and sawgrass marshes, that included well-developed
periphyton communities.
Today, the canal system is a conduit for nutrient transport. Nutrient loading in stormwater
from the EAA and urban areas has significantly increased phosphorus concentrations in
the downstream Water Conservation Areas, causing eutrophic impacts to these wetland
systems. Among the progressive eutrophic impacts are altered periphyton communities,
loss of water column dissolved oxygen, increased soil phosphorus content, conversion of the
wet prairie-sawgrass mosaic to dense single-species stands of cattail with no open water,
and consequent loss of wading bird foraging habitat. These collective changes impact the
structure and function of the aquatic ecosystem.'72'73' By about 1990 over 40,000 acres of
the Everglades were estimated to be impacted.'74'
In 2005 Florida adopted a 10 ppb water quality criterion forTP in the Everglades Protection
Area (EPA, Figure 42).'75' The objective of the criterion is to prevent nutrient-induced
imbalances in natural populations of aquatic flora or fauna. The criterion is applied as a long-
term average, with achievement of the criterion within the Everglades waterbody determined
by data collected monthly at fixed long-term marsh sampling locations. Compliance is
determined by a 4-part test specifying that: 1) the five year geometric mean averaged across
all stations is less than or equal to 10 ppb; 2) the annual geometric mean averaged across
stations is less than or equal to 10 ppb for three of five years; 3) the annual geometric mean
averaged across all stations is less than or equal to 11 ppb; and 4) the annual geometric
mean at all individual stations is less than or equal to 15 ppb. Each of the four parts must
be met to achieve the criterion. The test is intended to simultaneously allow for the natural
temporal and spatial variability that is observed at marsh reference sites, to be sensitive
57
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
enough to detect long-term increases in TP above 10 ppb, and to place an upper limit on
phosphorus at individual marsh locations. The test is applied separately, but in the same
manner, at impacted and unimpacted stations, with impacted areas defined as those where
the total phosphorus concentration in the upper 10 centimeters of the soil is greater than 500
mg/kg. For the Park, compliance with the criterion is determined not by the 4-part test at
marsh stations but rather by P concentration requirements at Park inflow structures. Since
R-EMAP data are not collected monthly at fixed sample sites, it is not appropriate to apply
Florida's 4-part test to R-EMAP marsh data. However, because of R-EMAP's probability-
based design, statements about the area of the marsh that exceed 10 ppb can be made for
individual R-EMAP sampling events.
The Park and Refuge have an additional level of water quality protection because
they have been designated by Florida as Outstanding Florida Waters (OFW). This anti-
degradation designation requires that the quality of water that existed the year prior to March
1,1979 must be maintained. This stricter OFWdesignation has been interpreted to require a
long-term average TP concentration of 7 ppb at a network of 14 interior marsh stations in the
Refuge, and a long-term average of 8 ppb at inflows to the Park at Shark Slough and 6 ppb
at inflows to Taylor Slough.'76'77'78' In addition, CERP has adopted the following performance
measure for surface water phosphorus: The TP concentration is not to exceed 10 ppb
for both the annual geometric mean at
marsh stations and the flow-weighted
annual geometric mean at water control
structures, and should not exceed OFW
concentration levels.'81
A phosphorus control program
was initiated in the 1990s in order to
prevent further loss of Everglades plant
communities and wildlife habitat due
to phosphorus enrichment. The initial
phase of this unprecedented program
required that discharges from the EAA
into the Everglades be at 50 ppb TP
or less. Control is to be achieved by a
combination of about 47,000 acres of
constructed treatment wetlands within
the EAA (the Everglades Construction
Project), referred to as Stormwater
Treatment Areas (STAs) (Figure 42), and
Stormwater
Treatment
Areas
FIGURE 42. Location of phosphorus control program
Stormwater treatment wetlands. In combination with
agricultural best management practices they are to
decrease phosphorus to about 10 ppb prior to discharge
into the EPA such that the 10 ppb TP criterion is met
throughout the waterbody (adapted from SFWMD).
58
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
agricultural Best Management Practices (BMPs). Agricultural BMPs were required to be
in place by 1995. The 1993 to 1996 R-EMAP Phase I sampling period corresponds to the
phase-in period for EAA BMPs, as during these years the percentage of EAA farms with
phosphorus control BMPs in place went from 0 to 100. Full BMP implementation began in
1996 with a 25% TP load reduction required. From 1996 to 2006 the BMP program resulted
in greater than a 50% TP load reduction from the EAA basin to the Everglades Protection
Area, as compared to the load that would have been expected without BMPs. Post-BMP
TP concentrations for WY2006 were 119 ppb, with a 44% load reduction.'481
TOTAL PHOSPHORUS
SURFACE WATER
The first STA (3700 acres or about 9% of the initial treatment acreage) began discharging
in 1994. There are presently six EAA STAs that have been constructed by the South Florida
Water Management District and the Army Corps of Engineers, with a WY2006 effective
treatment area of about 32,980 acres.'48' If all six EAA STAs and their treatment cells are
fully operational, the effective treatment area of the 47,000 acres will be 41,261 acres. These
STAs are in addition to the 36,000 acres of proposed
CERP constructed wetlands mentioned previously.
Flow-weighted annual mean TP inflow to the STAs
for WY2006 varied from 104 ppb for STA-6 to 213
ppb for STA-1W, with an average inflow for all STAs
of 144 ppb. STA outflow concentrations ranged
from 21 ppb for STA 2 to 146 ppb for STA 1E, with
an average outflow across all STAs of 44 ppb. The
overall load reduction for the STAs was 69%. The
cumulative amount of phosphorus retained from
1994 to 2006 was about 810,000 kg.'48'
Florida has developed a comprehensive long-
term plan for achieving water quality goals for all
basins that discharge into the Everglades.'133' Such
an effort to treat large volumes of stormwater down
to 10 ppbTP is unprecedented. The plan recognizes
that additional control measures will be necessary
to ensure that all discharges to the EPA meet water
quality standards. Florida is proceeding with 18,000
acres of additional STAs within the EAA. The long-
term plan also addresses the basins other than
the EAA with various source controls and capital
improvement projects.
FIGURE 43. Surface water total phosphorus
concentration (ug/L) during November 2005.
59
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
g; 7O
0-30
20
1O
;t i mate of Marsh An
6 8 10 12 14 16 18
Total Phosphorus Concentration (ug/l_)
FIGURE 44. Surface water total phosphorus estimates of marsh area during November 2005.
WATER PHOSPHORUS
R-EMAP Program water and soil samples were analyzed for phosphorus and other
indicators of nutrient enrichment, such as nitrogen, chlorophyll a, and alkaline phosphatase
activity (Appendix I). The kind of plant communities and the presence or absence of
periphyton was noted at each station to enable statistical analysis of relationships between
nutrient enrichment and habitat in the Everglades ecosystem. The Program previously
documented that canal TP concentrations exhibit strong north to south gradients due to
stormwater pumping, with the highest TP concentrations in canals in the EAA during the
wet season (median of 149 ppb).(10) During the 1993-1994 wet season about 80% of the
canal miles in the EAA had TP concentrations greater than the initial TP control target of
50 ppb, and overall 44% of Everglades canal miles had water TP concentrations greater
than 50 ppb.<10>
The spatial pattern of TP during
the November 2005 sampling event
is depicted in Figure 43. At that
time 27.2 ± 7.5% of the marsh had a
TP concentration exceeding 10 ppb
(Figure 44). This proportion contrasts
strongly with 57.8 ± 7.8% during the
September 1995 sampling event. TP
data from selected fixed Stations for TABLE 3. Water total phosphorus concentrations
from selected fixed stations in the Everglades for WY2006
WY2006 in the Everglades system are (ppb).<48'89'™>
EAABMPs
STAs
Refuge
WCA2
WCA3
Park
INFLOW
144
67
27
24
10
OUTFLOW
119
44
-
INTERIOR
-
15
18
10
6
6O
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
TOTAL PHOSPHORUS
SOIL
Cattail
present
TOTAL PHOSPHORUS
SOIL
FIGURE 45. Program data for total phosphorus in soil as milligrams phosphorus per kilogram of soil (left)
and as micrograms phosphorus per cubic centimeter of soil (right).
summarized in Table 3. The right column shows the range of values obtained forthe interior
parts of the major sub-areas. This range occurs over slightly more than half (35% to 90%)
of the cdf curve for November 2005 (Figure 44), suggesting good correspondence between
R-EMAP data and other measurements.
SOIL PHOSPHORUS
Phosphorus in marsh soils can bean indicator of pollution. Previous investigators working
in portions of the Everglades with peat soils have documented the association of increasing
soil TP with cattail encroachment. Accordingly, elevated soil TP concentrations have been
used as indicators of enrichment: 700 mg/kg(79); 610 mg/kg(80); and 600 mg/kg.(20'81) Florida's
Everglades total phosphorus criterion rule specifies a definition of impacted as being where
soil TP exceeds 500 milligrams TP per kilogram of soil. CERP has a restoration goal of
decreasing the areal extent of the Everglades with soil TP > 500 mg/kg, along with maintaining
or reducing long-term average concentrations to 400 mg/kg or less.'8'
61
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
90
CO
£ 70
"5 50
= 40
o
(
•^Cgg^L— J "~
X^J^^/
/7/fr
W/J
///(/
/if? fi
//Its' ' / Estimate of Marsh Area 1995-96
l/jls' Lower 95% Confidence Interval 1995-96
tiff II Upper 95% Confidence Interval 1995-96
LS//J Estimate of Marsh Area 2005
J^H// Lower 95% Confidence Interval 2005
^gf£*^/ upper so% Confidence Interval 2005
(2gj?^~
) 200 400 600 800 1000 1200 14
Total Phosphorus Concentration in Soil (ug/g)
00
FIGURE 46. Soil total phosphorus estimates of marsh area wet seasons 1995-96 and 2005. About 25% of
the Everglades had soil TP exceeding 500 mg/kg in 2005, as compared to 16% in 1995-96.
Soil phosphorus is expressed in Figure 45
(left) on a mass basis as milligrams of phosphorus
per kilogram of soil. Results reported here are
similar to those obtained by others in 2003 for
the EPA.<82'83'84' Program data indicate that in
2005 the area of the Everglades with soil TP
concentrations exceeding 500 mg/kg was 24.5
± 6.4%, while 49.3 ± 7.1% of the 2063 square
miles sampled exceeded 400 mg/kg (Figures
45 and 46). This contrasts with 16.3 ± 4.1%
exceeding 500 mg/kg in 1995-96, and 33.7 ±
5.4% exceeding 400 mg/kg. Figure 47 shows
the most recent (2003-2005) soil TP data at 1270
locations from all of the programs sampling in
the Everglades (R-EMAP, University of Florida
-SFWMD, and Florida or federal permit transect
monitoring). Depicted as mg/kg, WCA3A north
of Alligator Alley, northern WCA 2A, and the
edges of the Refuge most proximate to canals
have the highest soil phosphorus in the portion
of the Everglades underlain by peat soil (Figure
47). There are also several locations throughout
southern WCA 3A and the Park with soil TP in
excess of 500 mg/kg. However, these locations
FIGURE 47. Soil total phosphorus for 2003-2005
at 1270 locations from all sampling programs. Red dots
indicate soil TP > 500 mg/kg. Data are from SFWMD,
FDEPandUSEPA.
62
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
1600
1000
800
600
400
200
Soil TP
(mg/kg)
n Median
I I 25%-75%
"T" Non-Outlier Range
o Outliers
& Extremes
Refuge WCA 2 WCA 3N WCA 3S S. Slough Park
n Median
I I 25%-75%
~| Non-Outlier Range
o Outliers
as Extremes
Soil TP
(ug/cc)
have no corroborative second
indicator of enrichment such
as water TP exceeding 10
ppb, presence of cattail,
or altered periphyton
communities. These specific
higher soil TP concentrations
are likely reflective of differing
soil types and do not indicate
nutrient enrichment. USEPA
has noted that soil TP
concentrations in the 300-
600 mg/kg range may not be
an appropriate indicator of
enrichment for mineral soils
within the Everglades.'85'
Testing for statistical
differences across Program
sample years systemwide
indicates that the 2005 wet
season soil TP was higher
than the 1995-96 wet season
(median of 390 mg/kg versus
343 mg/kg). Others have
also documented increases
in Everglades soil TP in
recent years. A spatial expansion of elevated soil TP within WCA 2A was documented from
1990 to 1998, such that the WCA 2A median changed from 516 mg/kg to 860 mg/kg over
this seven-year period.'86' Analysis of soil TP data within WCA 3A collected from 1992 and
2003 indicate that the area with soil TP > 500 mg/kg increased from about 21 % to 30% over
these 11 years.'83' Additionally, transect sampling along TP gradients in the Refuge and
WCA 2A in 1989 and 1999 indicated expansion of the area with soil TP > 700 mg/kg.'79'
The 10 ppb long-term geometric mean water quality criterion for TP that applies
throughout the EPA has been calculated to translate into an equivalent annual flow-weighted
concentration of about 16 ppb at discharges into the Everglades.'87'88' This flow-weighted
limit has not been formally adopted. However, it is useful to calculate the amount of recent
Refuge
WCA3S S. Slough
FIGURE 48. Soil total phosphorus concentration by sub-area as
mg/kg (top) and ug/cc (bottom).
63
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
-A*
phosphorus loading into the Refuge and WCAs 1, 2 and 3 that is in excess of this flow-
weighted concentration. For example, during WY2006 about 169,200 kg (169.2 metric
tons, or mt) of TP was discharged into the EPA excluding the Park, which had TP inflows
at a flow-weighted mean concentration of only 9 ppb.(datafrom89> Had the water discharged
into the Refuge and WCAs 2 and 3 been at a flow-weighted TP concentration of 16 ppb,
this load would have been 42 mt. Therefore, the excess TP load into the Everglades during
WY2006 was about 127.2 mt (38.8 mt into the Refuge, 3.6 mt into WCA2 and 84.8 mt into
WCA 3), even though the STAs retained 176.6 mt(48)and the agricultural BMP program is
reported to have resulted in the removal of 117 mt prior to discharge of this stormwater into
the STAs or the EPA.(118) The excess TP load into the EPA is calculated to be 103.4 mt for
WY2005 and 73.5 mtfor WY2004. Excess TP loads also occurred each year from
WY1990 to WY2004. This excess TP is a potential explanation for the recent increases in
soil TP within the Everglades Protection Area.
Soil percent organic matter and bulk density vary greatly throughout the Everglades
due to differences between organic peat soils and inorganic marl soils. Soil bulk density
is low in peat soils (typically < 0.12 g/cc), and high in calcitic or marl soils (median of
0.36 g/cc for Park marl soils, Figures 38 bottom). Soil TP can also be expressed on a
volume basis as micrograms TP per cubic centimeter of soil in order to reflect the reality
of different Everglades soil types. When soil TP is adjusted for bulk density (Figure 45
right), the locations in southern WCA SAthat were above 500 mg/kg no longer have high
phosphorus. Areas in the Park with higher bulk density become distinct, although these
areas are known to be oligotrophic. Peat soils with higher TP are generally limited to
WCA 2A and the edges of the Refuge. The Refuge interior and portions of the Park have
the lowest soil phosphorus. Figure 45 right indicates that WCA 3A south of Alligator
Alley does not have high soil TP as ug/cc. These observations are consistent with
monthly surface water TP data from fixed marsh stations at these locations which have
annual geometric mean TP concentrations <10 ug/L(72) Testing for statistical differences
across Program sample years systemwide indicates that the 2005 wet season soil TP,
expressed as ug/cc, was no different than the 1995-96 wet season.
64
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
NITROGEN
Nitrogen is another plant nutrient that can contribute to eutrophication. Because the
Everglades marsh is phosphorus-limited,'72'73'119'nitrogen has not been a major concern. The
water quality criterion fortotal nitrogen that applies to the Everglades is a narrative: nutrient
concentrations shall not be altered so as to cause an imbalance in natural populations of
aquatic flora or fauna. CERP has adopted an Everglades restoration goal of less than or equal
to the baseline mean during 1994-2004; however, this baseline has not been defined.'8'
Surface water Total Nitrogen (TN) during November 2005 had a distinct spatial gradient,
with the highest concentrations above 1.0 mg/L found generally in WCA2Aand at two Refuge
stations (Figure 49 left). The overall median and arithmetic mean were both 0.58 mg/L. An
average of 86% of the surface water nitrogen was in organic forms. Surface water nitrogen
TOTAL NITROGEN
SOIL
NOVEMBER 2005
TOTAL NITROGEN
SURFACE WATER
NOVEMBER 2005
FIGURE 49. Surface water total nitrogen concentration (left, mg/L) and soil total nitrogen concentration
(right, percent) during November 2005.
65
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
-A*
gradients throughout the Everglades have been previously reported. During 1978-1982 the
five-year mean nitrate concentration entering the Park in western Shark Slough was 0.012
mg/L, as compared to 0.938 mg/L at the S-8 structure which discharges stormwater from
the EAA.(38) For 1978-1987 the mean TN concentration at pumps discharging stormwater
from the EAA were 3.4 to 6.0 mg/L, with inflows to the Park at 2.0 mg/L(114). During water
year 2006, total nitrogen concentration varied at water control structures, depending upon
proximity to the EAA. The median inflow TN concentration to the Park was 0.99 mg/L, as
compared to 2.4 mg/L for the Refuge. The annual median interior concentration in the Park
was 1.2 mg/L as compared to 2.4 mg/L for the Refuge.'89'
Nitrogen cycles in water bodies in organic and inorganic forms. Nitrification is the oxidation
of ammonium to nitrate, the nitrogen form assimilated by many plant species. Denitrification
is the reduction of nitrate to nitrogen gas, which can leave the water body and enter the
atmosphere. Although denitrifcation is a potential pathway for nitrogen loss from Everglades
surface waters, this pathway is not major. Previous studies have found that only 10% of
nitrogen was lost from peat soils to denitrification, 34% was lost from marl soils'92', and the
rate of removal increased as soils became more phosphorus-enriched.'92'93'
The organic peat soils of the Everglades have a TN content of about 1% to 4.4%, while
the marl soils of the Park generally have a TN content of <1% (Figure 49 right). The peat
soils of the EAA, which originated from Everglades sawgrass, are also reported at about
1% to 4%.'94' The major source of agricultural nitrogen in the EAA is the soil itself, with no
fertilizer additions of nitrogen necessary for sugarcane and minimal additions necessary for
vegetables.'94' Drainage water from the EAA is reported to export TN at rates ranging from
30-46 kg N/hectare/year<94'and 12-40 kg N/hectare/year.'95' During WY2006 the inflows to
STAs 1W, 2, 3/4 and 5 had flow-weighted mean TN concentrations of 3.9, 4.0, 3.8 and 1.6
mg/L respectively, while the outflow concentrations averaged 3.0, 2.5, 1.9 and 1.3 mg/L.
The STAs removed a minimal to moderate amount of TN, with treatment efficiencies of
19% to 50%.'48' The five-year TN treatment efficiency for STA-1W is reported at 26%, as
compared to 79% for TP.'47'
66
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
MACROPHYTES and PER1PHYTON
FIGURE SO. Mosaic of tree islands, sawgrass marsh and wet prairies within Shark Slough, Everglades
National Park. The brownish color is the periphyton mat at the water surface in wet prairies. This photo was
taken during the wet season when water depths were about 3 feet.
PLANT COMMUNITIES
The Everglades are defined by a unique mosaic of
vegetation community types (Figure 50). Wet prairies
and open water sloughs devoid of dense emergent
macrophytes serve as preferred habitats for foraging
wading birds.(96) These areas are also the Everglades
wetland type with the greatest diversity of native flora
and fauna.(30) Factors driving vegetation community
composition include hydroperiod, salinity, nutrients, and
disturbances such as fire, frosts, and hurricanes. During
2005 the Program conducted three types of plant analyses
at the 228 biogeochemical stations.
Field crews recorded the dominant plant community
at each sample point based on visual observation (Figure
51). The dominant community was identified as sawgrass
(Cladium jamaicense) at 58% of the 228 sites, and the
wet prairie-slough complex occurred at 32% of the sites.
Wet prairie is prevalent in the Refuge, and in wetter
FIGURE 51
portions of WCA 3. Sawgrass tends to dominate north during 2005.
Macrophyte
Community
Dominant plant community
67
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
of Alligator Alley and in WCA2, while the Park contains a mix of the two communities. The
remaining sites were other, minor community types (4%) and cattail (Typha domingensis)
stands (5%).
TOTAL PHOSPHORUS
SOIL
Plants were also studied quantitatively on-station in 2005. Program crews recorded
macrophyte species frequency in twenty 0.25-square meter quarter-quad rats arranged along
10-metertransects. One random transect associated with the biogeochemical sampling point
was established at all 228 stations. At stations where a second community was present within
practical distance of the point, a representative transect was established in that type. During
the 2005 dry season sampling event 143 plant taxa were found. Cluster analysis of all these
data identified three widespread
plant associations in the Everglades
marsh - a cluster dominated by
sawgrass; a cluster dominated by
deeperwaterspecies, such as white
water lily (Nymphaea odorata) and
various bladderworts (Utricularia
spp); and a cluster dominated by
spikerush (£. cellulosa) and purple
bladderwort (U. purpurea). These
latter two clusters are refered to
in this report as wet prairie-slough
communities. Six invasive, exotic
species (not native to North America)
were also documented - melaleuca
(Melaleuca quinquifolia), climbing
fern (Lygodium microphyllum),
Brazilian pepper (Schinus
terebinthefolius), Australian pine
(Casuarina sp.), salvinia (Salvinia
minima), and primrose-willow
(Ludwigia peruv/ana).'12'97'
Using the same classification
system (jointly developed specifically
for the Everglades by SFWMD
F.GURE 52. Soil total phosphorus (mg/kg) and cattail scientists, R-EMAP investigators,
presence based on Program data. and Others)'12' 120)that was used on
Cattail
68
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
Low phosphorus conditions must be restored if natural
Everglades periphyton and plant communities are to be maintained.
the Phase II (1999) Program
stations, 1 square kilometer
centered on each 2005 R-EMAP
station was mapped digitally.
Each station was mapped
twice, using aerial photographs
taken in 1994-95 and in 2003-
04. Change detection analysis
of these data is ongoing. Using
the imagery from 1994-95,
SFWMD recently completed
the first classified vegetation
map of WCA3.(99) Sawgrass
and wet prairie communities
accounted for 87.5% of this
WCA. Cattail occupied 5% of
the Area, with large expanses
in the northern part. Building
on the work done for Phase
II, the R-EMAP sample maps
will be compared to the entire
WCA3 map, to demonstrate the
feasibility of inferring change
over wide areas based only
on sampling at the 1 square
kilometer scale.
Cattail is a native
species known to respond to
phosphorus enrichment such
that it can replace wet prairies
and sawgrass. Conversion of
wet prairies to dense cattail constitutes a loss of the prefered foraging habitat for wading
birds.(98) There is a strong association between the presence of this invasive species and
elevated soil phosphorus or proximity to canals. Cattail was commonly encountered in the
northern portions of WCA 3A (attributed to drying conditions and soil mineralization) and
FIGURE 53. Presence or absence of cattail during 2003-2005 at
1270 Everglades stations sampled by all programs. Red dots indicate
cattail was present. Data are from SFWMD, FDEP and USEPA.
69
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
'V .
4
WCA 2A (attributed to enrichment from stormwater), and at sites that were close to canals.
Cattail presence throughout the EPA was also documented during 2003 for the SFWMD soil
phosphorus sampling project. Figure 53 shows the presence or absence of cattail at the 2003
SWFMD and 2005 R-EMAP stations combined (1270 locations). The expanse of cattail in
northern WCA3 is evident, as it is in peripheral portions of the Refuge and WCA 2. Based
on the transect quadrat data, cattail was documented as being present, but not necessarily
dominant, at 19% of the R-EMAP sites sampled in 2005. Comparable data are not available
for earlier phases of the Program due
to refinement of methods.
PERIPHYTON
Well-developed attached or floating
calcareous periphyton mats are a
defining characteristic of the hard water
Everglades, particularly wet prairies FlGURE 54. Epiphytic periphyton (bottom) formerly
and deeper Slough areas (cover and surrounding an Eleocharis stem (top).
Periphyton Presence
May 2005
Periphyton Presence
November 2005
FIGURE 55. Presence of epiphytic, floating and benthic periphyton during 2005.
7O
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
FIGURE 56. Well-developed periphyton community at short-hyrdroperiod marsh within the Park. Floating
and epiphytic forms are visible.
Figures 54 & 56). These conspicuous microscopic plants serve multiple functions such as
providing oxygen to the water column for fish, removing calcium carbonate from the water
and depositing it as soil, removing phosphorus from the water to very low concentrations,
and serving as the base of the local food web.(72) Hydroperiod and water depth, water ions,
and phosphorus concentration all affect periphyton extent and structure.'131' Periphyton
communities are sensitive to very slight increases in nutrient concentrations, with increases
in phosphorus causing changes to the periphyton assemblage, including species composition
and biomass, or even the disappearance of the entire mat. Consequently, periphyton are
a sensitive and important indicator of marsh ecosystem status.'73'100'
Periphyton mats were found at 63% of the 228 sample sites during 2005, as compared
to 67% of the sites during 1995-1996. The species composition of 2005 periphyton will be
documented in companion reports. During 2005 three types of periphyton growth forms
were sampled: benthic mats which are at the sediment surface (Figure 36 bottom), epiphytic
mats which are attached to emergent macrophytes (cover and Figure 54), and floating mats
that are distinct from macrophytes (Figure 56). The most common form of periphyton was
epiphytic, which was observed at 103 or45 % of the stations (Figure 55), followed by benthic
(25%) and floating (11 %). Benthic mats were most common in the marl, short-hydroperiod
portions of the Park. There were no periphyton mats encountered in the soft water Refuge,
the eutrophic portion of WCA2A, and parts of northern WCA3A. With the exception of the
Refuge, the areas where periphyton mats were not found tend to be areas where wet prairies
are absent and dense sawgrass or cattail dominate. In communities where plant density,
height, and above ground biomass are high, shading effects may preclude the development
of periphyton mats and wet prairie communities.'101' Elevated phosphorus may also explain
the absence of the mat community, or a change in periphyton species composition to species
that are more nutrient tolerant and not mat-forming.'73'
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
MERCURY CONTAMINATION
Since about 1990 mercury contamination has
been a concern in the Everglades. Elevated
mercury in gamefish caused Florida to issue fish
consumption advisories to protect human health.
These advisories either ban or restrict consumption
of nine species of gamefish from over two million
acres encompassing the Everglades (Figure 57).
There is a ban on consumption of largemouth bass
longer than 14 inches.(102) The existence of these
advisories means that the Everglades waterbody does
not meet the "fishable" portion of its designated use.
In addition, ecological risk assessments and mercury
dosing studies have indicated that populations of
top predators in the Everglades could be adversely
affected by mercury contamination, such that mercury
accumulation through the food web may reduce the
health or breeding success of wading birds'28'103'116'117'
and the Florida panther.'104'
Florida's class III surface water criterion for total
mercury is 12.0 nanograms per liter (ng/L or parts per
trillion). Since 1995, 733 different locations within the
EPA have been sampled by Program personnel for
total mercury in surface water. The overall median of
those data is 2.0 ng/L, asitwasfortheNovember2005
sampling (Figures 58 and 64). Only 6 of 733 samples
exceeded the 12.0 ng/L surface water criterion. These
6 samples were all collected during the dry season
at shallow marsh sites (water depths from 0.1 to 0.7
feet). During 2005 the highest concentrations occured
in the northern Everglades (Figure 64). Statistical
testing for differences across sampling phases within
season indicates that there was a very slight, but
significant (p<0.05), increase in surface water total
mercury during the wet season in 2005 as compared
to 1995. Dry season concentrations were higherthan
WARNING
The Florida Department of Health and Rehabilitative
Services has issued a health advisory urging limited
consumption of largemouth bass and warmouth
caught in certain portions of the Everglades due to
excessive accumulation of the element mercury.
»Fish caught in Arthur R Marshall Loxahatenee
National Wildlife Refuge (Water Conservation Area
1) should not be eaten more than once per week by
adults and not more than once per month by
children under 15 and pregnant women.
• Fish caught in Water Conservation Areas 2a and 3
should not be eaten at all.
Rnr additional information, contact the Florida
Department of Health and Rehabilitative Services at
C«os) ass-som —"«••*
FIGURE 57. Young fisherman at the Refuge
boat ramp (top); fish consumption advisory to protect
human health at the same boat ramp (bottom).
72
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
en
o yn
<
C5
s so
0
o 4U
O or*
c
__- —^^^^^
^s^s^—^
/f^S
M
I
III
ill
III
j
j
0
) 1 2 3 4 5 6
Total Mercury Concentratior
-
^^~ Estimate of Marsh Area
Lower 95% Confidence Interval
Upper 95% Confidence Interval
7 8 9 10
in Surface Water (ng/L)
11 1
2
FIGURE 58. Estimates of marsh area for wet season total mercury concentration in surface
water during November 2005.
wet season concentrations. Bioaccumulation of mercury to unacceptable levels in gamefish
is occurring although the 12 ng/L surface water criterion is being met.
Elemental mercury deposited into surface water from the atmosphere can be converted
to methylmercury (MeHg) by bacteria in the presence of sulfate and organic carbon.(56'64)
Methyl mercury is the toxic form of mercury that bio-accumulates and biomagnifies in the
aquatic food chain. There are no numeric water quality standards for methylmercury in
surface water. However, Florida water quality standards require that there shall be no
substances in concentrations which injure, are chronically toxic to, or produce adverse
physiological or behavioral response in humans, plants or animals.(123) Numerous factors
affect the bioaccumulation of mercury in aquatic life.'113' Some of these factors include the
length of the aquatic food chain, soil type, pH, and dissolved organic material.(105) In the
Everglades during the last decade about 30 factors have been suggested by various scientists
as playing a role in mercury bioaccumulation. Interrelationships among the factors are
poorly understood and may be waterbody specific. Because of these complexities, USEPA
recently concluded that in orderto protect human health it is more appropriate to have a fish
tissue residue water quality criterion for methylmercury rather than a water column-based
water quality criterion. The resulting methylmercury water quality criterion recommended
by USEPA is a fish tissue residue criterion of less than 300 ug/kg.(105) About 95-99 % of
the mercury that is found in top predator tissue is in the methyl form.'106'
73
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
-A*
A 2007 status report from the Everglades mercury program states that'24':
• 71 % of the largemouth bass sampled in the WCAs in 2005 exceeded the recommended
fish tissue criterion of 300 ug/kg, while 100% of the largemouth bass from Shark Slough in
the Park exceeded this criterion;
• mercury dropped in bass in the WCAs from a median of about 1500 ug/kg in 1991 to
about 300 ug/kg in 2001 but then increased to about 500 ug/kg in 2005. However mercury
has simultaneously increased in bass in portions of the Park, where during 2005 the median
was about 1200 ug/kg;
• mercury concentrations in wading bird feathers have declined since 1998, except for
in the Park;
• there was no trend in wet deposition of mercury from 1994 to 2005 in the Park.
Mosquitofish have been sampled for the duration of the Program. This species is an
ideal indicator of mercury contamination for several reasons: They are the most abundant
fish in the Everglades and they are found throughout the canals and in all marsh habitats'110';
they are easily sampled; they are in the food web for gamefish and wading birds, so they
provide insights that are relevant to both ecological health and human health; and, their
average lifespan is several months and they have a small home range, so they integrate
mercury exposure over a short time frame in a discrete area. During the four wet season
sampling events conducted by the Program, mosquitofish have been successfully collected
at 96% of the 414 Everglades marsh sites, including wet prairie, sawgrass and cattail
habitats. Everglades mosquitofish are a secondary consumer and have been reported to
be at trophic level 2.0 to 3.0'115' and 4.0 to 4.5.'107' Everglades mosquitofish consume animal
prey (crustaceans, insects, arachnids), algae, detritus and plant matter.'115'
During 1995-1996 the Program documented a pronounced spatial gradient in mosquitofish
mercury, with the highest concentrations in remote portions of WCASAand extending into
Shark Slough in the Park.'9'12'13' This same spatial pattern, with the highest concentrations
in WCAS and the Park, was documented again in 2005 (Figures 59 and 62). These results
are consistent with those for other biota that indicate the highest mercury concentrations
in the Everglades occur in the Park or WCA 3 for largemouth bass,'24'great egrets,'24' and
alligators.'26' A recent risk assessment on the effects of methylmercury on great egrets
concluded that birds foraging in the Park have a high probability of exceeding the acceptable
daily mercury dose level and cumulative dose level necessary to protect nestlings and pre-
nesting females. There is also a high probability of exceeding the lowest adverse effects
level.'105'
The United States Fish and Wildlife Service has recommended a level of 100 ug/kg
74
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
TOTAL MERCURY
MOSQUITOFISH
WET SEASON 1995
TOTAL MERCURY
MOSQUITOFISH
WET SEASON 2005
FIGURE 59. Mosquitofish mercury during wet season sampling 1995 and 2005.
100 -
<
2
Estimate of Marsh Area 2005
Lower 95% Confidence Interval 2005
Upper 95% Confidence Interval 2005
Estimate of Marsh Area 1995
Lower 95% Confidence Interval 1995
Upper 95% Confidence Interval 1995
100
200 300 400
Total Mercury Concentration in Mosquitofish (ng/g)
500
600
FIGURE 6O. Mosquitofish mercury concentration estimates of marsh area during September 1995 and
November 2005.
75
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
(micrograms per kilogram, or parts per billion) in prey fish in order to protect top predators
such as wading birds from mercury contamination.'108' During the 2005 wet season sampling,
40.1 (± 6.7) % of the marsh had mosquitofish mercury concentrations that exceeded 100
ug/kg (Figure 60). This proportion is in contrast to the 59.9 (± 7.3) % found during the 1995
wet season sampling. USEPAhas recommended a concentration of 77 ug/kg at trophic level
600
300
100
Ye
,r
E
199
j-96
I
19
. Median
~T~ Non-Outlier
. Extreme,
1 '
t
1
1
' {
' 1 ^
1
99 2005
?ange
600
500
100
Ys
ar
199
1
5-96
'
19
. Median
"T" Non-Outlier Range
i* Extremes
99 2005
FIGURE 61. Box and whisker plots of mosquitofish mercury concentration (ug/kg) throughout
the Everglades by Program phases during the dry season sampling (left) and wet season sampling
(right).
FIGURE 62. Mosquitofish mercury during November 2005. Yellow bars are concentrations > 200 ppb,
red bars are >50 ppb and < 200 ppb, light green are < 50 ppb, white dots indicate that field crews were
unsuccessful in efforts to collect fish.
76
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
3 for protection of birds and mammals.'109' During the 2005 wet season sampling, 64.7 (±
7.3) % of the marsh had mosquitofish mercury concentrations that exceeded 77 ug/kg. This
proportion is in contrast to 70.5 (± 7.1) % found during the 1995 wet season sampling.
Statistical testing for differences between cdf curves indicates that during the dry season
and the wet season there was a significant and pronounced drop in mosquitofish mercury
concentration from 1995 to 1999 (wet season p < 0.01; dry season p « 0.001) and again
from 1999 to 2005 (wet season p < 0.01; dry season p < 0.01). This result is consistently
supported by krigs (Figure 59), box-and-whisker plots (Figure 61), and the z-test for
differences between means. Program data also indicate a significant drop in methylmercury
concentration in all forms of periphyton during the dry season throughout the three Program
phases. The test for differences between cdf curves for methylmercury in surface water
during the 2005 wet season, as compared to 1995-96, indicates a significant (p«0.001)
but slight drop (median changed from 0.29 ng/Lto 0.21 ng/L).
Program data indicate extremely high bioaccumulation of mercury in Everglades biota.
November 2005 median concentrations for total mercury were as follows (Appendix II):
surface water, 2.2 parts per trillion; floating periphyton, 15.5 parts per billion (ppb); benthic
periphyton, 9.7 ppb; mosquitofish, 87 ppb; floe, 130 ppb; sediment, 140 ppb. Median
methylmercury concentrations were: surface water 0.2 parts pertrillion, floating periphyton
1.6 ppb; benthic periphyton 0.47 ppb; epiphytic periphyton 1.7 ppb; floe 3.0 ppb; sediment
0.49 ppb.
The bioaccumulation
factor (BAF) is an indexthat
expresses the degree to
which mercury accumulates
in fish compared to its
concentration in surface
water.'129' 130> The highest
surface watertotal mercury
and methylmercury
concentrations occur in
WCA 2 and the northern
Everglades (Figure
64), while the highest
mercury concentrations in
mosquitofish occur to the
9
8
7
6
5
4
3
2
1
0
C
*
n
* "°
* °
* *
•
*• *• *
* * *
: ..°.-.
* ** * n + *
*** tl +44* * *** '
* n nOl "-"Ml D C
.
•*
*
* ,
•D ** * ^ 1
[j n B cn
] n H 1
* Total Mercury in Si
n MethylmercLrry"rn"S
:*•
}f : %
p-i p
n n P '
rface Water (ng/L)
urfac-e-Water (ng/t) — :
*
•
,
• •
•
n
n DD
*
a
50 100 150 200 250 300 3£
Total Mercury Concentration (ng/g) in Mosquitofish
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
FIGURE 63. Scatterplot of November 2005 mosquitofish mercury
versus surface water methylmercury (right axis) and total mercury (left
axis) for the entire study area. Mosquitofish mercury concentration is not
correlated with surface water mercury concentration.
77
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
TOTAL MERCURY
SURFACE WATER
NOVEMBER 2005
METHYL MERCURY
SURFACE WATER
NOVEMBER 2005
TOTAL MERCURY
BIOCONCENTRATION
FACTOR
NOVEMBER 2005
METHYL MERCURY
BIOCONCENTRATION
FACTOR
NOVEMBER 2005
FIGURE 64. Total mercury concentration in surface water during November 2005 (top left),
methyl mercury concentration in surface water (top right), mercury bioconcentration factor from
surface water methylmercury to mosquitofish (bottom right) and mercury bioconcentration factor
from surface water total mercury to mosquitofish (bottom left).
78
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
There has been a sharp decline in mercury concentrations in preyfish from 1995/96 to
1999 to 2005, although concentrations remain too high to protect top carnivores.
south in WCA 3A and the Park (Figure 58). Bioaccumulation factors were calculated as the
concentration of mercury in mosquitofish divided by the concentration of methylmercury in
surface water (BAFm) (Figure 64 bottom). Bioaccumulation factors were also calculated as
the concentration of mercury in mosquitofish divided by the concentration of total mercury
in surface water (BAFt). BAF varies in space by a factor of about ten with the highest BAF
observed in the areas to the south with the higher concentrations in mosquitofish. The
median BAFm was 4.7 x 105 with values as high as 2.1 x 106 in the Park.
Pearson correlation coefficients were calculated for about 50 parameters versus total
mercury in fish, and versus BAFs (Appendix III). The parameters most highly correlated
with fish mercury were methylmercury in all periphyton forms combined (r= 0.58, p<0.001),
methylmercury in epiphytic periphyton (r=0.68, p=0.001) and TP in floe (r=-0.58, p<0.001).
Floe is non-consolidated biogenic detrital matter (Figures 15 and 65) that is an important
food web component for Everglades invertebrates
and fish.'111' During November 2005 floe was
present at 77% of the sampling sites, with a
thickness of up to 39 cm (Figure 65). The strong
correlation between mercury in periphyton and
mercury in mosquitofish is not surprising given
that periphyton are integral to their food web.(107)
There was no correlation between fish mercury
and surface watertotal mercury or methylmercury
(Figure 63), and there was no correlation between
fish mercury and forms of carbon. The fact that
the high water column total mercury and methyl
mercury in WCA 2 and the Refuge do not result
in high mercury in fish may be due to an inhibitory
mechanism. Mosquitofish mercury is correlated
with DOC-normalized water methylmercury, but
not water methylmercury itself.'112' The highest
surface water DOC and porewater sulfide
concentrations in the EPA are found in WCA 2
(Figures 32 and 33). Sulfide and carbon have
been reported to inhibit methylation.'50'63'64' FIGURE 65. Fioc thickness during November
2005
Program data corroborate this finding. The
Floe Thickness
November 2005
79
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
parameters most highly correlated with BAFm were surface water DOC (r= - 0.65, p<0.001),
porewater sulfide (r= - 0.63, p<0.001), porewatersulfate (r= - 0.54, p<0.001) and MeHg in
floating periphyton (r= - 0.47, p=0.047). The parameters most highly correlated with BAFt
were surface water alkaline phosphatase activity (r= 0.57, p<0.001) and floe TP (r= - 0.56,
p<0.001).
In order to identify constituents relevant to
the pronounced drop in mosquitofish mercury
observed in Program data from 1995 to 2005, a
core area was recognized where the high mercury
concentrations in fish occurred in 1995 (Figure 66).
Pearson correlation coefficients were recalculated
for November 2005 using only stations within this
area. The highest correlation coefficients with
fish mercury were surface water MeHg (r= 0.47
p<0.001), floe TP (r= - 0.48 p=0.004), sediment
MeHg (r= 0.41 p=0.001) and MeHg in epiphytic
periphyton (r= 0.42 p=0.002). The parameters
most highly correlated with BAFm were MeHg in
floating periphyton (r= - 0.94 p<0.001) and water
depth (r= - 0.53, p<0.001). The parameter most
highly correlated with BAFt was sediment MeHg
(r= 0.46 p<0.001). MeHg in surface water was
most correlated with MeHg in floating periphyton
(r= 0.87 p<0.001) and surface water sulfate (r= 0.65
p<0.001). MeHg in benthic periphyton was highly
correlated with surface water sulfate during the wet
season (r= 0.87 p<0.001).
FIGURE 66. Core area of highest mosquitofish
mercury during wet season sampling 1995.
BO
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
The Everglades R-EMAP Program consistently documents conditions throughout
the Everglades in a quantitative manner. This documentation provides a basis for
determining the effectiveness of Everglades protection and restoration activities.
CONCLUSION
This report has touched on many aspects of the biogeochemical environment of the
Everglades. As with any assessment of the environment at large, the long-term goal of
the Everglades R-EMAP Program is to first describe, then diagnose, and finally to predict
the status of the ecosystem. This report summarizes major parts of the first step for the
2005 iteration of the Program. Beyond that description, statements have been made about
changes in the state of the system. The diagnosis step, initiated here, will be developed
further with multivariate statistical analysis. Hopefully, models will come from these analyses
to enable trend-casting and confident prediction of responses to CERP actions, and mercury
and phosphorus control efforts, to a degree that will facilitate adaptive management. The
next task for R-EMAP investigators will be to broaden the ecological scope of the description,
while intensifying efforts to elucidate predictive relationships leading from physico-chemical
drivers, through fluxes between environmental compartments, and to responses of ecological
endpoints. Future publications will address topics not included here, such as studies of
aquatic food webs, periphyton species composition, and landscape-scale habitat change.
Program data and metadata are available to the public from USEPA [http://www.epa.gov/
region4/sesd/sesdpub_completed.html.] Suggestions from the public, scientists, managers,
and stakeholders in South Florida for improving the Program are welcome, and will be
incorporated to the extent practicable, when the availability of funding becomes sufficiently
favorable to begin planning for Phase IV.
81
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EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM
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Monitoring and Assessment Program, U.S. Environmental Protection Agency. 252 pp.
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achieving water quality goals.
88
-------
Appendix I. Measurements and Analytes by Medium, with abbreviations, for Everglades R-EMAP 2005.
SURFACE WATER (SW)
Depth
Temperature
Dissolved Oxygen
In-situ pH
Conductivity (COND)
Turbidity
Total Phosphorus (TP)
Soluble Reactive Phosphorus
Total Nitrogen (TN)
Total Inorganic Nitrogen (TIN)
Total Organic Nitrogen (TON)
Filtered Ammonia (FNH4)
Filtered Nitrate (FNO3)
Filtered Nitrite (FNO2)
Filtered Nitrate-Nitrite (FNN)
Dissolved Organic Carbon (DOC)
Sulfate (SO4)
Sulfide (H2S)
Alkaline Phosphatase Activity (APA)
Chlorophyll-a (CHLA)
Total Mercury (THg)
Methylmercury (MeHg)
MUF Phosphorus
MUF Carbon
Chloride (CL)
Bromide
Fluoride
N15 (in suspended particulate organic matter)
C13 (in suspended particulate organic matter)
SOIL (SD)
Type
Thickness
Ash-Free Dry Weight (AFDW)
Bulk Density (BD)
Mineral Content
Water Content
In-situ pH
Acid Volatile Sulfide
Methane
Carbon Dioxide
Total Carbon (TC)
Total Nitrogen (TN)
Total Phosphorus, by mass (TP... 1)
Total Phosphorus, by volume (TP...2)
MUF Phosphorus
MUF Carbon
Total Mercury (THg)
Methylmercury (MeHg)
FLOC (FC)
Thickness
Ash Free Dry Weight
Bulk Density
Mineral Content
Water Content
Methane
Carbon Dioxide
Total Carbon (TC)
Total Nitrogen (TN)
Total Phosphorus (TP)
MUF Phosphorus
MUF Carbon
Total Mercury (THg)
Methylmercury (MeHg)
Chlorophyll-a
PERIPHYTON [PE (epiphytic), PB (benthic),
PF (floating), PS (sum of all forms present)]
Bulk Density
Ash Free Dry Weight
Methylmercury (MeHg)
Total Mercury (THg)
Carbon:Nitrogen:Phosphorus Ratio
MOSQUITOFISH
Total Mercury (THgFish)
weight
length
sex
PORE WATER (PW)
Oxidation-Reduction Potential (Eh)
Soluble Reactive Phosphorus
Total Inorganic Nitrogen (TIN)
Filtered Ammonia (FNH4)
Filtered Nitrate (FNO3)
Filtered Nitrite (FNO2)
Filtered Nitrate-Nitrite (FNN)
Dissolved Organic Carbon (DOC)
Sulfate (SO4)
Sulfide (H2S)
Chloride
Bromide
Flouride
-------
Appendix II. Median Values of Selected Parameters for the Everglades R-EMAP Program.
Analyte Medium Season Phase Units*
1995-96 1999 2005
Entire Study Area
total mercury
total phosphorus
methyl mercury
total mercury
total mercury
methyl mercury
methyl mercury
total phosphorus
total phosphorus
methyl mercury
methyl mercury
methyl mercury
methyl mercury
methyl mercury
methyl mercury
methyl mercury
methyl mercury
total mercury
total mercury
total mercury
total mercury
sulfate
total organic carbon
sulfide
Core Area
sulfate
total mercury
conductivity
total organic carbon
sulfide
total mercury
methyl mercury
total mercury
methyl mercury
total phosphorus
total mercury
methyl mercury
total mercury
methyl mercury
total mercury
methyl mercury
total mercury
methyl mercury
mosquitofish
surface water
surface water
surface water
mosquitofish
epiphytic periphyton
epiphytic periphyton
soil
soil
floe
floating periphyton
benthic periphyton
soil
floe
floating periphyton
benthic periphyton
soil
floe
floating periphyton
benthic periphyton
soil
surface water
surface water
pore water
surface water
mosquitofish
surface water
surface water
pore water
surface water
surface water
soil
soil
soil
floe
floe
epiphytic periphyton
epiphytic periphyton
benthic periphyton
benthic periphyton
floating periphyton
floating periphyton
dry
wet
wet
wet
wet
dry
wet
wet
wet
wet
wet
wet
wet
dry
dry
dry
dry
wet
wet
wet
wet
wet
dry
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
wet
185 a
8.68 a
0.28 a
1.86at
142a
2.35 a
2.13a
343 a
55.03
0.38 a
0.43 a
1.05a
0.52
106a
130
2.6 a
28.55 at
19.19at
2.0
215a
383 a
15.86a
1.68a
1 .64 at
0.28 a
140
0.47 ab
382 a
148a
2.26 a
105.8a
0.72 a
107 b
6.16 b
0.19b
1.9a
127b
1.72ab
2.31 a
0.83
1.73a
0.20 ab
0.39 b
0.2
2.19a
0.57 b
0.52
158a
38.2 a
29.7 b
130
2.05 a
0.11a
2.0
164 b
286 b
13.82b
0.09 a
1.63a
0.16b
140
0.37 a
145a
0.83
28.9 b
2.04 a
40.61 b
0.21 b
26.68 a
1.67a
52 c
7.50 c
0.21 c
2.2 b
87 c
1.45b
1.70a
390 b
54.25
3.00
1.60a
0.47 b
0.49 a
3.25
0.85 b
0.31 b
1.15
130b
15. 5a
9.70 b
140
2.00 b
22.58 b
17.20b
0.12a
2.0
110C
407 c
0.11a
1.9b
0.19b
140
0.54 b
410a
120b
2.90
22. Ob
1.80a
11.00b
0.52 ab
17.00a
1.60a
ng/g
ug/l
ng/l
ng/l
ng/g
ng/g
ng/g
mg/kg
ug/cc
ng/g
ng/g
ng/g
ng/g
ng/g
ng/g
ng/g
ug/kg
ng/g
ng/g
ng/g
ug/kg
mg/l
mg/l
mg/l
mg/l
ng/g
u mhos/cm
mg/l
mg/l
ng/l
ng/l
ug/kg
ug/kg
mg/kg
ng/g
ng/g
ng/g
ng/g
ng/g
ng/g
ng/g
ng/g
Distributions with medians having different letters are different (P < 0.05).
Units are nanograms per gram [(ng/g) parts per billion], micrograms per liter [(ug/l) parts per billion],
nanograms per liter [(ng/l) parts per trillion], milligrams per kilogram [(mg/kg) parts per million], micrograms per
cubic centimeter (ug/cc), micrograms per kilogram [(ug/kg) parts per billion], milligrams per liter [(ug/l) parts per
million], and micromhos per centimeter (umhos/cm).
T 1995 only. * 1996 only.
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About the authors
Peter Kalla is a senior scientist in the Ecology Branch at the USEPA Region 4 Laboratory.
He has 23 years of professional experience in wetland, watershed, and wildlife research and
management, including 19 years spent in the study of sub-tropical ecosystems in Florida.
He has led $4.7 million worth of work in wetland and watershed assessment and planning,
mostly within the R-EMAP and EMAP programs. He has also conducted research on the
use of remote sensing in demarcation and assessment of Coastal Plain wetlands. He is
an author on about 70 technical publications. Dr. Kalla has served as a natural resources
policy advisor to numerous local, state, regional, and national government agencies. He
received his B.S. in Zoology from Auburn University in 1975, his M.S. in Biology from
East Tennessee State University in 1979, and his Ph.D. in Ecology from the University of
Tennessee, Knoxville in 1991.
Daniel Scheldt serves as USEPA's Senior Scientist on South Florida and Everglades water
quality issues, advising senior managers regarding various scientific, policy, and regulatory
matters. He was employed at the South Florida Research Center at Everglades National
Park from 1982-1991 as a hydrologist where he directed hydrological monitoring and water
quality monitoring and research. He has 25 years of professional experience regarding
Everglades science. He is an author on about 50 technical reports or scientific publications
concerning water quality, mercury contamination, nutrient enrichment, environmental
assessment, or ecological risk assessment. He completed a M. S. in Environmental
Science with a concentration in Water Resources at the Indiana University School of Public
and Environmental Affairs in Bloomington.
Photographic Acknowledgements
Table of Contents: person in cattail, Phyllis Meyer; Figure 3: Everglades National Park;
Figures 8,14, 27, 29, 47, 53 and 62: satellite base map, South Florida Water Management
District; Figure 15: lower right, Mel Parsons; Figure 36: Danny Adams; Inside back cover:
Peter Kalla; All other photos: Daniel Scheldt.
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