Item B
aEPA
United States..
Environmental Protection
Agency
Water Quality Protection EP A 904-R-99-OOS
Program - Florida Keys September 1999
National Marine SanctuarY
WATER QUALITY CONCERNS IN THE
FLORIDA KEYS: SOURCES, EFFECTS,
AND SOLUTIONS
8/1(.0/00
B.
WATER QUALITY CONCERNS IN THE FLORIDA KEYS:
SOURCES, EFFECTS, AND SOLUTIONS
PREPARED BY
WILLIAM L. KRUCZYNSKI
PROGRAM SCIENTIST
FLORIDA KEYS NATIONAL MARINE SANCTUARY
WATER QUALITY PROTECTION PROGRAM
SEPTEMBER 1999
TABLE OF CONTENTS
WATER QUALITY PROTECTION PROGRAM
STEERIN"G COMMITTEE..... .............................. .... ................................ . . I
TECHNICAL ADVISORY COMMITTEE................................................. 11
MANAGEMENT COMMITTEE................................................................ IV
FOR MORE INFORMATION
WATER QUALITY PROTECTION PROGRAM...................................... V
FLORIDA KEYS NATIONAL MARINE SANCTUARy......................... V
EXECUTIVE SUMMARy............... ............................. ...................................... . . VI
INTRODUCTION................................................................................................... 1
HISTORY AND PHYSICAL SETTING................................................................. 3
CHANGING TIMES............................................................................................... 5
WATER QUALITy................................................................................................ 6
EUTROPHICATION.............................................................................................. 8
SOURCES OF WATER QUALITY CONCERNS.................................................. 11
STORMW A TER RUNOFF......................................................................... 11
W ASTEW A TER.......................................................................................... 12
OTHER SOURCES............................................................ ....................... . .. 13
CANALS AND OTHER CONFINED WATERS.................................................... 15
OTHER NEARSHORE WATERS........................................................................... 23
OUTER CORAL REEFS.......................................................................................... 25
GROUNDWATER.................................................................................................... 27
FECAL COLIFORM BACTERIA AND DISEASE ORGANISMS......................... 30
EFFECTS ON BIOLOGICAL COMMUNITIES....................................................... 32
EXAMPLES OF AREAS WITH SIMILAR PROBLEMS......................................... 36
AUSTRALIA.................................................................................................. 37
ST. LUCIE COUNTy.................................................................................... 37
TAMPA BAY ................................................................................................. 38
OPTIONS FOR CORRECTING WATER QUALITY PROBLEMS......................... 39
ONSITE DISPOSAL SySTEMS.............. .............. ......................... .............. 39
PACKAGE PLANTS..................................................................................... 41
CENTRAL SEW AGE SySTEMS................................................................. 43
MARATHON AREA WASTEWATER FACILITIES PLAN
AND PHASED IMPLEMENTATION FOR LITTLE VENICE....... 45
MONROE COUNTY W ASTEW ATER MASTER PLAN......................... 47
CESSPIT IDENTIFICATION AND REPLACEMENT................................ 48
CANAL BEST MANAGEMENT PRACTICES........................................... 49
DISCHARGES FROM VESSELS....................................................... .......... 51
STORMW A TER TREATMENT................................................................... 52
CARRYING CAP ACITY.......................................................................................... 54
MONITORING.......................................................................................................... 55
WATER QUALITy....................................................................................... 55
HARD BOTTOM AND CORALS................................................................. 56
SEAGRASSES...........................................................................................:... 57
ECONOMICS OF CLEAN WATER AND NATURAL RESOURCES.................... 58
TABLES.. .................................................................................................................. 61
FIGURES.................................................................................................................... 73
LITERATURE CITED............................................................................................... 83
FLORIDA KEYS NATIONAL MARINE SANCTUARY
WATER QUALITY PROTECTION PROGRAM
STEERING COMMITTEE
John H. Hankinson, Jr., Regional Administrator
U.S. Environmental Protection Agency
Region 4
Kirby B. Greene, ill, Deputy Secretary
Florida Department of Environmental Protection
Jeff Benoit, Director
Ocean and Coastal Resosurces Management
National Oceanic and Atmospheric Administration
Richard G. Ring, Superintendent
Everglades National Park
Colonel Joe R. Miller, District Engineer
U.S. Army Corps of Engineers
Jacksonville District
Tom Grahl
U.S. Fish and Wildlife Service
Steven M. Seibert, Secretary
Florida Department of Communities Affairs
Bart Bibler, Bureau Chief
Water and Onsite Sewage Program
Florida Department of Health
Mile Collins, Chairman
Governing Board
South Florida Water Management District
James C. Reynolds, Deputy Executive Director
Florida Keys Aqueduct Authority
1
Commissioner Nora Williams
Board of County Commissioners
Monroe County
William H. Botten
City of Key Colony Beach
Commissioner Jimmy Weekly
City of Key West
Charley Causey
Florida Keys Environmental Fund
Fran Decker, Chairman
Citizens Advisory Council
Florida Keys National Marine Sanctuary
Karl Lessard
Monroe County Commercial Fishermen
TECHNICAL ADVISORY COMMITTEE
Dr. John C. Ogden, Director
Florida Institute of Oceanography
Dr. Eugene A. Shinn
U.S. Geological Survey
Center for Coastal Geology
Dr. Jay Zieman
University of Virginia
Department of Environmental Sciences
Dr. Alina Szmant
University of Miami
Rosenstiel School of Marine and Atmospheric Science
George Garrett
Director of Marine Resources
Monroe County
ii
Dr. Erich Mueller
Mote Marine Laboratory
Pigeon Key Marine Research Center
Dr. Ronald Jones, Director
Southeast Environmental Research Program
Florida International University
Dr. Kalthleen Sullivan
University of Miami
Department of Biology
Dr. Brian Lapointe
Harbor Branch Oceanographic Institute
Curtis Kruer
Consulting Biologist
Summerland Key, FL
Chris Schrader
Tavernier, FL
Dr. Roland Ferry
U.S. Environmental Protection Agency
Coastal Programs Section
Dr. Robert Brock
Everglades National Park
Dr. Kevin Sherman
Florida Department of Health
Joyce Newman
Big Pine Key, FL
Dr. Steven L. Miller
NOAA
National Undersea Research Center
Walt Jaap
Florida Marine Research Institute
111
John Hunt
Florida Marine Research Institute
Gus Rios
Florida Department of Environmental Protection
Susan Loder
Florida Keys Aqueduct Authority
Steve Traxler
U.S. Army Corps of Engineers
Richard Allemen
South Florida Water Management District
MANAGEMENT COMMITTEE
Fred McManus, Florida Keys Coordinator
U.S. Environmental Protection Agency
Dr. William L. Kruczynski
Florida Keys Program Scientist
U.S. Environmental Protection Agency
Billy Causey, Superintendent
Florida Keys National Marine Sanctuary
National Oceanic and Atmospheric Administration
G.P. Schmahl
Florida Keys National Marine Sanctuary
Florida Department of Environmental Protection
Ken Haddad, Director
Florida Marine Research Institute
Florida Department of Environmental Protection
George Garrett
Director of Marine Resources
Monroe County
IV
FOR MORE INFORMATION ON THE WATER QUALITY PROTECTION PROGRAM,
CONTACT:
William L. Kruczynski
Florida Keys Program Scientist
P.O. Box 500368
Marathon, FL 33050
(305) 743-0537
Fred McManus
Florida Keys Coordinator
U.S. Environmental Protection Agency- 4
61 Forsyth Street, S.W.
Atlanta, GA 30303-8960
(404) 562-9385
FOR MORE INFORMATION ON THE FLORIDA KEYS NATIONAL MARINE
SANCTUARY, CONTACT:
Billy Causey, Superintendent
Florida Keys National Marine Sanctuary
National Oceanographic and Atmospheric Administration
P.O. Box 500368
Marathon, FL 33050
(305) 743-0537
v
EXECUTIVE SUMMARY
The Florida Keys are a chain of tropical islands composed of several interdependent
community types, including tropical hardwood forests, fringing mangrove wetlands, seagrass
meadows, hard and soft bottoms, and coral reefs. The tropical setting and ecological diversity
have made the Florida Keys a popular place to live and vacation.
The natural communities that make up the Florida Keys ecosystem exist in a dynamic
equilibrium, which means that changes that result in a direct impact to one community type can
have profound effects on adjacent communities. The continued existence of the Keys marine
ecosystem is dependent upon maintenance of clear waters with relatively low nutrients.
Historically, development in the Keys relied on the use of cesspits and septic tanks which
provide little treatment of domestic wastewater in porous lime rock substrates. In addition,
stormwater runs untreated into nearshore surface waters. Lack of nutrient removal from
domestic wastewater and stormwater has resulted in the addition of nutrient-rich waste waters
into confined waters and adjacent nearshore areas. The cumulative effects of these discharges
have led to water quality degradation of these inshore areas.
The following statements on water quality issues in the Florida Keys are supported by the
literature and knowledge of scientists:
1. There is a rapid exchange of groundwater and surface waters in the Keys that is driven
by tidal pumping.
2. Cesspits are not appropriate for disposal of wastewater because they are illegal,
provide very little treatment, and are a health hazard. Cesspit effluent can rapidly migrate
to surface waters.
3. Properly functioning septic tank systems remove very little nutrients (4% N, 15% P)
from wastewater and, depending upon their location, effluent from septic tank drainfields
can rapidly migrate to surface waters.
4. Sewage discharged from cesspits and septic tanks are a source of nutrients and human
pathogens to ground and surface waters.
5. Contaminants in stormwater runoff contribute substantially to the degradation of
nearshore water quality.
6. Water quality problems due to on-site sewage disposal practices and stormwater
runoff have been documented in residential canals. Water quality parameters that are
VI
degraded include nutrient enrichment, fecal coliform contamination, and biochemical
oxygen demand.
7. Long, dead-end canal systems, deep canals of any length, and poorly flushed basins
accumulate weed wrack and other particulate matter.
8. The water column of many canals over six feet deep is stratified and bottom waters are
usually in violation of Florida's Class ill Surface Water Quality Standard for dissolved
oxygen. Because they usually violate Class ill Surface Water Quality Standards, canals
were excluded from Outstanding Florida Waters designation.
9. Artificial aeration of canals does not eliminate the sources of excessive nutrients in
canal waters but may result in better mixing which may facilitate nitrogen cycling.
10. Improving flushing of degraded canal systems may improve the water quality within
the canal, but will also result in adding additional nutrients to the adjacent waters.
11. Canal systems and basins with poor water quality are a potential source of nutrients
and other contaminants to other nearshore waters.
12. Seagrass beds located near the mouths of some degraded canal systems exhibit signs
of eutrophication, such as increased epiphyte load and growth of benthic algae.
13. Vessel generated turbidity (re-suspended sediments) is a growing concern in many
areas with high boat traffic including canals and open waters.
14. Aerobic treatment units and package plants provide secondary treatment, removing
80% - 90% of the total suspended solids (TSS) and organic wastes that are responsible for
biochemical oxygen demand. In poor soil conditions with high groundwater tables,
where drainfields are rendered inefficient, secondary treatment systems are better than
septic tanks at removing organically bound nutrients associated with the TSS. These
systems, however, are not designed to remove dissolved nutrients.
15. Disposal of wastewater from package treatment plants or on-site disposal systems
into Class V injection wells results in nutrient enrichment of the groundwater. However,
it is not known whether discharges into Class V wells results in substantial nutrient
loading to surface waters. This question is currently under investigation.
16. In areas where groundwater is saline, injected wastewater is buoyant and rapidly rises
to the surface.
17. Recent tracer studies have demonstrated rapid migration of Class V effluent to
surface waters (hours to days). These studies demonstrated that tracers were greatly
VB
diluted before reaching surface waters and that some phosphorus was stripped from
groundwater by the substrate. The long term ability of phosphorus stripping by the
substrate is currently under investigation.
18. Sewage discharges from vessels degrade the water quality of marinas and other
confined water anchorages.
19. Florida Bay discharge, oceanic and Gulf of Mexico upwelling and currents, rainwater
and other natural sources add nutrients to surface waters of the Keys.
20. Net water movement through the tidal passes between the Keys is toward the Atlantic
Ocean. Once entering Hawk Channel, water direction and speed is controlled by
prevailing winds and ocean currents.
21. Coral habitats are exhibiting declines in health; coral diseases are more common and
benthic algae have increased in abundance and spatial coverage.
22. There are no definitive studies on the geographic extent of the impact of
anthropogenic nutrients. Scientists agree that canal and other nearshore waters are
affected by human-derived nutrients from sewage. Improved sewage treatment practices
are needed to improve canal and other nearshore waters. Impacts further from shore that
may be due to anthropogenic nutrients may be reduced or eliminated by cleaning up
nearshore waters.
23. Planning and implementation of improvements to wastewater treatment are
underway. A cesspit identification and on-site disposal certification program has been
initiated. A Marathon Area Feasibility Plan has been completed and a Monroe County
Wastewater Master Plan has been initiated. Funding is being sought for planning, design,
and construction of wastewater and stormwater infrastructure.
24. A long term monitoring program has been implemented to provide information on
the status and trends of water quality, coral, and seagrass communities.
25. The costs of water quality improvements are a small fraction of the long term asset
value that natural resources, such as reefs, hard bottoms, and seagrasses, provide to the
economy of the Florida Keys.
If sources of nutrient enrichment continue unabated, it is likely that the ecological balance
of nearshore communities of the Keys will be changed. Changes in the structure and function of
nearshore communities could result in stresses to other components of the Keys ecosystem.
Since the economy of the Keys is directly linked to a healthy ecosystem, it is imperative that
sources of excessive nutrients to this ecosystem be eliminated. In recognition of the warning
signals of degraded water quality, the U.S. Environmental Protection Agency and the State of
viii
Florida, in conjunction with the National Oceanic and Atmospheric Administration, have, at the
direction of Congress, prepared a Water Quality Protection Program (WQPP) for the Florida
Keys National Marine Sanctuary. Full implementation of the WQPP will help reverse the trend
of environmental degradation and restore and maintain the Florida Keys marine ecosystem.
IX
INTRODUCTION
The Florida Keys are a chain of tropical islands surrounded by clear ocean
waters teeming with sea life. The uniqueness and diversity of natural communities
combine to make the Florida Keys ecosystem one of the "crown jewels" of our
Nation's natural treasure chest.
The Keys ecosystem is composed of several interdependent community
types, including tropical hardwood forests, fringing mangrove wetlands, seagrass
meadows, hard and soft bottoms, and coral reefs. This ecological diversity has
made the Keys a popular place to live and an important vacation destination.
The current population of the Keys is approximately 78,000 permanent, year-
round residents (1990 census). The population increases by about 25,000 during
peak tourist season (winter months). Approximately 70 percent of Keys residents
regularly participate in water-based activities, such as fishing (48%), snorkeling
(45%), beach activities (38%), and observing wildlife and nature (36%) (Leeworthy
and Wiley, 1997). Maintenance of the integrity and ecological health of marine and
terrestrial environments is critical to the economy of the Keys. Approximately 3
million visitor trips annually are made to the Keys totaling over 16 million person
days. Visitors generate over $1.3 billion in direct output and tourism supports over
21,800 jobs in the Keys (English et al., 1996). Tourists come to the Keys for a
variety of reasons: snorkeling (28%), scuba diving (8%), fishing (21 %), wildlife
observation (28%), beach activities (34%), and sightseeing (55%) (Leeworthy and
Wiley, 1997).
Shallow water environments surrounding the Keys constitute extensive
nursery areas and fishing grounds for a variety of commercially and recreation ally
important marine species. Monroe County ranks fIrst in Florida in total volume of
seafood landed (10% of State landings). In 1990, 19.7.million pounds of fin fish,
shellfish, and other aquatic organisms were landed in Monroe County with a
dockside value of $48.4 million (Adams, 1992). The spiny lobster is the most
valuable harvest (>$20 million annually). Monroe County accounts for 91 % of the
total spiny lobster harvest and 44% of total harvest of pink shrimp and stone crab
(Adams, 1992).
1
The natural communities that make up the Florida Keys ecosystem exist in a
dynamic equilibrium. Changes to the physical-chemical conditions that result in a
direct impact to one community type can have profound effects on adjacent
community types. For example, coastal fringing wetlands filter upland runoff,
stabilize sediments, and absorb some nutrients. Thus, wetlands help maintain clear,
relatively nutrient poor waters that facilitate luxuriant growth of seagrasses in
adjacent waters. Upsetting this balance by removing wetland vegetation, can result
in a localized increase in nutrients and turbidity in nearshore waters that may reduce
seagrass coverage. Coastal wetlands and seagrasses are important habitats for
juvenile fishes, and a reduction in spatial coverage of these habitats can result in
decreased fish populations that can further upset ecosystem functions. Loss of
wetlands and seagrasses can increase water turbidity due to re-suspension of
sediments previously bound by their root systems that can have additional negative
impacts on adjacent communities. Thus, subtle, single changes can have profound,
cascading effects throughout the entire ecosystem.
Human activities have negatively impacted the ecological balance of the
Florida Keys ecosystem (Voss, 1988). Cumulative, large-scale physical impacts,
such as construction of barriers to tidal flushing, dredging and filling of seagrass
beds and wetlands, and nutrient addition to waters surrounding the Keys have
profoundly influenced the physical appearance of the Keys, as well as the balance
of ecosystem functions. The impacts of many human activities are obvious, such as
the approximately 30,000 acres of seagrasses which have been propeller scarred by
boaters in the Keys (Sargent et al., 1995). Other impacts, such as water quality
degradation, may not be immediately obvious to the casual observer. However,
nutrient loading is a widespread factor that alters structure and function of aquatic
ecosystems in coastal watersheds (Valiela et aI., 1992).
The survival of the existing Florida Keys marine ecosystem is dependent
upon clear, low-nutrient waters. This paper is a summary of available information
of nearshore water quality (canals, basins, and waters immediately adjacent to the
Keys). The data demonstrate that the cumulative effects of continued discharges of
nutrient-rich wastewater and stormwater into confined and some other adjacent
nearshore waters has degraded the water quality of those waters (Barada and
Partington, 1972; U.S. Environmental Protection Agency, 1975; Florida
Department of Environmental Regulation, 1985, 1987, 1990; Lapointe et al., 1990;
Lapointe and Clark, 1992). There is evidence that the degraded water quality has
2
adversely impacted other nearshore communities (Lapointe and Clark, 1992;
Lapointe et aI., 1994; Lapointe and Matzie, 1996). If sources of nutrient
enrichmentcontinue unabated, it is likely that the ecological balance of nearshore
communities of the Keys will be changed. Changes in nearshore community
structure and function could result in stresses to other components of the Keys
ecosystem. Since the tourist-based economy of the Keys is directly linked to a
healthy Keys ecosystem, it is prudent to work diligently toward eliminating sources
of excessive nutrients to this ecosystem.
Restoration of degraded portions of the Keys aquatic ecosystem may be
possible, but it will require the combined effort of the entire community of the
Florida Keys, with help from federal and State governments. Collectively, we are
the stewards of this unique national treasure and restoring and maintaining this
ecosystem is a national goal. In recognition of the warning signals of degraded
water quality, the V.S. Environmental Protection Agency (EPA) and the State of
Florida, in conjunction with the National Oceanic and Atmospheric Administration,
have, at the direction of Congress, prepared a Water Quality Protection Program
(WQPP) for the Florida Keys National Marine Sanctuary. It is hoped that full
implementation of the WQPP will reverse the trend of environmental degradation
and restore and maintain the Florida Keys marine ecosystem.
HISTORY AND PHYSICAL SETTING
The Florida Keys are a chain of limestone islands that extend from the
southern tip of the Florida mainland southwest to the Dry Tortugas, a distance of
approximately 220 miles. The Keys are island remnants of ancient coral reefs
(V pper Keys) and sand bars (Lower Keys) that flourished during a period of higher
sea levels about 125,000 years ago (Pleistocene) (Hoffmeister and Multer, 1968;
Shinn, 1988; Lidz and Shinn, 1991). During the last ice age, that started about
100,000 years ago, sea level dropped and exposed the ancient coral reefs and sand
bars that form the present Keys. At that time of lower sea level, the Florida land
mass was much larger than it is today and Florida Bay was forested. Sea level
began to rise as polar ice caps started melting about 15,000 years ago; that resulted
in re-flooding of some of the exposed land and led to our present-day geography.
The existing outer coral reef tract that parallels the Florida Keys on the Atlantic
Ocean side began forming between 6,000 and 10,000 years ago. Reef growth rate
ranges from 0.61 to 4.85 meters (2 to 16 ft) per 1000 years (Shinn et al., 1977).
3
A continued rise of sea level resulted in flooding what we now call Florida
Bay about 4,000 years ago. At that time, coral communities thrived along the entire
seaward edge of the Keys. As
sea level rose further, it resulted in the establishment of tidal passes between the
Keys. This was a significant event since it resulted in the export of terrestrial
material, sediments, and organic matter from Florida Bay to the Atlantic through
the tidal passes. The export of that material resulted in conditions that no longer
favored lush coral reef development in the regions of the major tidal passes (Middle
Keys) (Ginsburg and Shinn, 1964; Shinn et al., 1989; Lidz and Shinn, 1991; Shinn
et aI., 1994a; Ogden et aI., 1994).
Florida Bay is a shallow embayment composed of basins separated by mud
banks and mangrove islands. Water quality in Florida Bay is highly variable.
Discharges of either hot or cold water, with very high or low salinity, from Florida
Bay through the tidal passes further limited development of the outer coral reefs.
To the north and west of the Middle Keys, where the reef tract is more sheltered by
the keys from waters discharged from Florida Bay, vigorous coral reef growth
continued (Lidz and Shinn, 1991; Shinn et al., 1989). Thus, prior to human impacts
in south Florida, water exchange between Florida Bay and the Atlantic Ocean
significantly impeded coral growth in the areas of major tidal passes.as well as
offshore.
Today, the Florida Keys outer reefs are a disjunct series of bank reefs that are
located at the northern zoogeographic boundary of tropical waters. Because it is at
the northern limit of coral reef development, the Keys reef tract regularly
experiences natural stresses, such as winter temperatures below those normally
associated with vigorous coral reef development. Also, the reef experiences higher
summer temperature extremes than many other reefs in the Caribbean basin
(Vaughn, 1918).
The Keys themselves consist of limestone rock formations. In the upper
Keys, these rock formations are composed of Key Largo Limestone, which is the
skeletal remains of the ancient Pleistocene reef. The lower Keys, Big Pine Key and
west, were formed by deposition and consolidation of sand bars (Miami Oolite)
over the underlying Key Largo limestone. Over time, vegetation began growing on
the exposed surfaces of the limestone and thin veneers of soils formed in some
areas from weathering of limestone and accumulation of organic matter from plants.
4
The Keys were vegetated from seeds, propagules, and uprooted or detached
plant material carried from the Florida mainland and from Caribbean islands. This
has resulted in a curious mix of tropical and subtropical vegetation in this unique
geographic setting. Prior to the arrival of Europeans, the Keys consisted of diverse
West Indian tropical hardwood forests on high ground,
pine rocklands and freshwater wetlands on the interiors of larger islands (e.g., Big
Pine Key), and vast expanses of mangrove wetlands that surrounded the islands and
extended into tidal waters.
The waters surrounding the Keys were clear and supported an abundance
and diversity of plant and animal life. Shallow areas were vegetated by acres of
lush seagrasses in areas where sediments accumulated. Hard and soft corals thrived
where limestone was exposed under the water. Large populations of queen conchs,
sea turtles, and many species of sea life were supported by the productivity of this
diverse, shallow-water ecosystem. The shallow water and coral reef communities
evolved in a low nutrient subtropical sea environment and the continued existence
of this ecosystem is dependent upon maintenance of relatively low sediment and
nutrient conditions.
CHANGING TIMES
Although known to exist, the Florida Keys were largely uninhabited during
the sixteenth, seventeenth, and eighteenth centuries, even though waters just
offshore provided a major shipping route to and from Europe. During that time, the
islands were occupied by Keys Indians, some settlers, and pirates who preyed on
sea traffic. Scarcity of fresh water and the lack of a vast expanse of fertile soil
prevented the populous settlement of the Keys. Undoubtedly, mosquitos and
disease also played a major role in the lack of development in the Keys.
After Florida was ceded by Spain to the United States in 1821, Key West
became an important military post, and island trade began to grow. Trading,
fishing, cigar making, recovering goods from shipwrecks, and a limited agriculture
base provided livelihoods for Keys residents (Viele, 1996). The Overseas Railway
and Overseas Highway, completed in 1912 and 1938, respectively, connected the
Keys to the mainland through a series of filled causeways and bridges. This
transportation system, together with a water pipeline from the mainland built to
5
supply the military in Key West during World War II, set the stage for post-war
development of the Keys (Halley et al., 1997). The attractive climate, inexpensive
land, beauty of the coral reefs, clear waters with abundant fishes, diversity of
wildlife, and mosquito control all combined to make the Keys a very popular place
to live and vacation.
Much of the physical alteration of the Keys to support the growing human
population occurred during the 1950's through the 1970's. During that period,
many acres of tropical hardwood hammocks were cleared to provide land for
housing and commercial development. The attractiveness of waterfront
development prompted the creation of "fastland" through dredging and filling of
mangrove forests and seagrass beds to construct networks of finger-fill residential
canals. More than 200 canals and access channels were dredged during that period
(FDER,1987). Turbidity from the dredging and filling operations smothered
adjacent areas of hard bottom and seagrass habitats. Many canals were dug 10- to
20-feet deep to maximize the production of fill material excavated from the canal,
and most canal systems were designed as long, dead-end networks with little or no
tidal flushing at their upper ends. In general, water quality of newly dug canals was
the same as areas of adjacent nearshore waters due to lack of input of nutrients from
runoff and development.
WATER QUALITY
The concept of what constitutes "good" water quality is complex. The
definition of acceptable water quality is based upon several interrelated parameters,
including how the water will be used (e.g., drinking, swimming, fishing),
concentrations of materials in the water above natural background levels that could
have a deleterious effect on plants or animals (pollution), and the presence of
compounds not usually found in the water (contamination). Parameters typically
measured during routine water quality studies are salinity, dissolved oxygen,
turbidity, biochemical oxygen demand (BODs), chlorophyll, fecal coliform, and
nutrient concentrations, predominantly nitrogen and phosphorus (Table 1).
Contaminants include heavy metals, pesticides, herbicides, and other chemicals.
Water quality standards are acceptable limits for materials found in water and
are defined in regulations. State of Florida water quality criteria are contained in
Chapter 62-302 Florida Administrative Code. Rule 62-302.530 includes standards
6
for Class III marine waters. Water quality standards for drinking water include
acceptable levels, i.e. numeric limits, of odor, taste, color, pollutants, and
contaminants. These standards are aimed at reducing or eliminating compounds
that are displeasing or potentially hazardous to people who drink the water.
Defining environmental water quality standards is more complex than
drinking water standards and must be evaluated in an ecological and aesthetic
context. Water quality standards are based on conditions that may result in a
change in the quantity or health of the organisms that live in the water. However,
because even pristine natural ecosystems undergo changes in response to natural
variations and all ecosystems gradually change over time, it can be difficult to
determine the exact point that changes in water quality parameters begin to cause
degradation of the ecosystem.
The waters surrounding the Keys have been declared as "Outstanding Florida
Waters" (OFW) by the State of Florida (FDER, 1985). By regulation, input of
materials that could be considered pollutants to open surface waters cannot exceed
the concentration of those materials that naturally occur in water. However,
ambient background conditions can change seasonally or at different phases of a
tidal cycle. From a scientific standpoint, the declaration of OFW status for the
waters of the Florida Keys does not solve the problem of defining acceptable limits
of pollution. The range of water quality parameters measured throughout the Keys
during a survey to support designation of the Florida Keys as OFW is given in
Table 2 (FDER, 1985). Because of the OFW designation, direct surface water
discharges of pollutants have been eliminated, or are being phased out.
In order to establish pollutant standards, the effects of the pollutants on
biological communities must be determined. Pollutant (or contaminant) levels
become unacceptable when they result in detrimental changes to an organism or the
biological community. This concept is easy to understand when the pollutant or
contaminant results in loss or replacement of a community or a species; no one can
argue against the fact that concentrations which cause death are unacceptable to the
community or species that died! Measurements must be sufficiently sensitive to
detect the subtle, non-lethal changes that can slowly result in shifts in species
dominance and community structure. These changes are signs that pollutants have
reached concentrations that are resulting in unacceptable changes to the natural
ecosystem. This threshold is called a non numeric or "narrative" water quality
standard.
7
In the Keys there are two main problems associated with wastewater
pollution: fecal contamination (health risk) and nutrient enrichment
(eutrophication). One important water quality standard concerns the presence of
fecal coliform bacteria in the water. Birds and mammals excrete fecal coliform
bacteria in fecal matter. The presence of fecal coliform bacteria in the water
column is used as a measure of possible wastewater contamination of the water.
Although fecal coliform bacteria are not a major health risk, they are easy to
measure and can indicate the presence of other enteric (intestinal), disease-
producing microbes. Presence of fecal coliform bacteria above the State standard of
800 colonies/100 m1 of water (monthly average) is indicative of contamination by
untreated sewage and is a public health concern. This bacteriological standard was
developed for fresh water. Fecal coliform bacteria normally die when exposed to
marine waters. However, fecal coliforms sometimes are present in tropical
environments in the absence of any source of fecal contamination (Hansen, 1988).
Therefore, it is questionable whether the existing standard is meaningful for marine
systems (Dutka et al., 1974; Goodfellow et al., 1977; Loh et al., 1979). Normally,
when fecal coliform bacteria are present in marine systems, it is an indicator of very
recent fecal contamination. Low concentrations of fecal coliform bacteria should
not necessarily be equated to low abundance of bacterial or viral pathogens in
marine waters.
Coprostanol is a chemical that is produced during the digestion process and is
a product of cholesterol decomposition. It is a better indicator of discharge of
untreated sewage because unlike fecal coliform bacteria which are relatively short-
lived in the marine environment, coprostanol accumulates in sediments and
provides a long-term record of sewage pollution. However, measurement of
coprostanol is impractical for routine monitoring because it requires sophisticated,
expensive analysis and, at the present time, there is no regulatory standard for
coprostanol.
EUTROPHICATION
Nutrients, such as carbon, nitrogen and phosphorus, are essential for the
normal healthy functioning of all living cells. They are used in biosynthesis in all
living matter. These nutrients and others, such as potassium and magnesium, which
are present in very small amounts, are recycled in the ecosystem. When organisms
8
excrete waste products or die, the nutrients present in the waste or carcass are made
available through the decomposition process. The growth of plants is generally
limited by the lack of one or more of these nutrients. New plant growth is
dependent upon this recycling of bound nutrients. In this manner, an ecosystem
maintains a "balance."
Ecosystems can utilize a certain amount of "new" nutrients. New nutrients may
come from other adjacent (upstream) natural systems or may be introduced by
human activities. Domestic wastewater is one major source of new nutrients to the
aquatic environment. If nutrients are released into the environment in excessive
amounts (eutrophication), they become pollutants because they disrupt the natural
nutrient balance and result in unacceptable changes of community structure.
Dramatic changes in community structure can result in a catastrophic collapse of an
ecosystem.
Eutrophication often progresses through a sequence of stages. A typical
progression involves: (a) enhanced primary productivity, (b) changes in plant
species composition, (c) very dense phytoplankton blooms, often toxic, (d) anoxic
conditions, (e) adverse effects on fish and invertebrates, and (f) changes in structure
of benthic communities (GESAMP, 1990).
There are many documented examples of the collapse of an ecosystem due to
nutrient enrichment. For the sake of simplicity, consider a simple pond ecosystem
that is rarely visited by people. The pond ecosystem is in balance because the
aquatic vegetation (grassbeds) that grow on the bottom of the pond supports a
population of shrimp, which in turn supports a population of fish. As shrimp and
fish grow and defecate, and eventually die, they return nutrients to the water which
are taken up by the grasses and support grassbed growth. If you (or a raccoon)
defecate or urinate into the pond, the nutrients that are added may result in
increased grass growth which may cover more area of the pond bottom. Increased
grassbeds will result in increased numbers of shrimp and bigger and more abundant
fish. Thus, the pond ecosystem can assimilate some additional new nutrients
without a significant negative change in structure or function.
However, if the area surrounding the pond becomes a popular campground,
and all the campers dump their wastewater directly into the pond, the structure of
the pond ecosystem will change drastically. Microscopic algae which were always
present in the pond, but were held in check by low amounts of available nutrients,
9
will grow, divide and result in an algal bloom that will change the water color from
clear to green. The green water (high chlorophyll) will absorb most of the sunlight
that strikes the pond and will result in the death of the aquatic grasses living on the
bottom of the pond. Death of the benthic grasses will result in death of the shrimp
that are dependent upon them. The fish that eat shrimp will also starve since they
are not physically able to eat algae. Death of the benthic grasses, shrimp, and fish
will result in the release of more nutrients into the water which will further fuel the
algal bloom. The small number of fish in the pond that can eat algae can now
explode in population size because of a seemingly unlimited amount of algae.
Ultimately, the blooms of algae and fish will cause the collapse of the ecosystem
when they respire at night, utilize all the dissolved oxygen, and die. This
hypothetical,
catastrophic collapse of a pond ecosystem is exactly the scenario that resulted in the
ecological collapse of Lake Erie, portions of Tampa Bay, and many other bodies of
water that received unacceptably high levels of nutrients. Addition of high levels of
nutrients result in major changes in ecosystem structure and function and can lead
to the eventual collapse of the ecosystem.
Generally, it is the total amount of nutrients, including micro-nutrients,
entering a water body that can result in overloading of the system, not necessarily
their concentration. It matters little whether nutrient addition comes from a single
or a few concentrated sources of nutrients discharging into a water body or from
many sources discharging lower concentrations of nutrients. The effect of the total
loading to the receiving water body will be the same. When the system can no
longer absorb increased levels of new nutrients without significantly changing
ecosystem structure and function, the threshold of nutrient assimilative capacity of
the system is reached.
A principal objective of wastewater treatment processes is to remove
nutrients and other pollutants and dispose of them in a manner that does not cause
unacceptable changes to the environment. Indeed, re-use of wastewater in suitable
areas may be used to cause desirable changes to the productivity of a cultivated
field or forest (e.g., land application of wastewater).
Tropical marine hard bottom and seagrass communities have evolved and
thrive in relatively low nutrient (oligotrophic) conditions. Species in these
communities efficiently take up nutrients and out-compete other less adapted
species in low nutrient environments. They can not successfully compete with
10
organisms that have evolved to take advantage of elevated nutrient loads.
Therefore, nutrients added to oligotrophic systems are very quickly taken up by
opportunistic species. Because of rapid uptake, nutrient concentrations in the water
can be quite low and may not be detectable using traditional water quality sampling
methods. Changes in the structure of the biological community (species abundance
and composition) are important signs of nutrient enrichment in oligotrophic
systems.
Nutrients are found in the foods, drinks, fertilizers, drinking water, and the
like that are imported into the Keys every day. If these new nutrients get into the
surface waters, they become available for use by the marine ecosystem. Small
additions of nutrients may cause inconsequential changes, but if continued or
increased over time, they can cause drastic shifts in the numbers and kinds of plants
and animals. The change to ecosystems due to excess nutrients is called
eutrophication, which means "too much food".
SOURCES OF WATER QUALITY CONCERNS
STORMWATER RUNOFF
Pollutants can be conveyed into surface waters when stormwater accumulates
on land surfaces and runs off. Stormwater is considered a major source of
pollutants to surface waters nationally. Runoff typically contains substances like
organic debris, silt, nitrogen, phosphorus, metals, and oils. The amount or load of
pollutants is largely a function of rainfall quantity, imperviousness (i.e. the degree
to which rainwater cannot soak into soil), and land use. In residential areas, for
example, nutrients are a major part of the load. Pollutants from roadways include
oils and metals. Soil characteristics can also playa major role in the types and
quantities of pollutants that are retained on land.
In Florida, the Water Management Districts and local governments now
impose a minimum level of stormwater treatment for all new developments. The
criteria are intended to protect surface waters according to their use classification.
Much of the development in the Florida Keys occurred prior to the existence of
these criteria. Similar to other parts of the State at the time, stormwater was
considered a nuisance since it resulted in flooding. Therefore, if stormwater
systems were employed at all, they were typically designed to efficiently convey
water off land surfaces as quickly as possible. These old systems are considered to
11
be the most liable to cause water pollution and, therefore, policies now in place seek
to retrofit them whenever possible. In most areas of the Keys, there was no
stormwater management. Uncontrolled runoff can cause pollution of surface
waters.
In the Keys, stormwater runoff from roadways, bridges, driveways and yards,
roof tops, and shopping center parking lots contribute stormwater loading to surface
waters. The amount of pollutant load caused by stormwater runoff can be estimated
mathematically from the factors given above. Estimates of total loadings of
nitrogen and phosphorus from wastewater and stormwater were summarized in the
Phase II Report of the WQPP (EPA, 1993) Assumptions used to generate those
figures were recently reevaluated and the numbers have bee revised (Table 4).
These recent estimates attribute about 20% of the nearshore nitrogen load and about
45% of the phosphorus to stormwatr (Table 4). These estimates, however, can vary
widely depending on the
magnitude of each factor. No estimate should be considered absolute, but viewed
only in relationship to its potential impact.
WASTEWATER
As is true for all animal life, humans derive nutrients and energy from the
food we eat. Weare not totally efficient in removing nutrients from our food, so
human waste contains nutrients, such as carbon, nitrogen, and phosphorus. Typical
residential wastewater flow is approximately 45 gallons per person per day. Of
that, approximately 35% (16 gallons) is from the toilet (black water) and 65% (29
gallons) is from sinks, bathtubs, and appliances (gray water) (Harkins, 1996).
Nutrient concentrations of pollutants in black water and gray water are summarized
in Table 3. Wastewater can enter canals and other nearshore waters from cesspits
(4,000 estimated), septic tanks (approximately 20,000), injection wells (750), ocean
outfalls (1), and live-aboard vessels.
Based upon current best estimates (Table 4), approximately 80% of nitrogen
loadings comes from wastewater. Onsite disposal systems (septic tanks and aerobic
treatment systems) and cesspits account for 40.3% of nitrogen loadings.
Approximately 55% of phosphorus loadings are from wastewater. Onsite disposal
systems and cesspits account for 33.2% of total phosphorus loadings.
Disposal of wastewater from live-aboard vessels is a significant localized
problem because of the low level of treatment, the tendency for live-aboard vessels
12
to congregate in certain marinas or anchorages, and potential adverse health effects
of discharging untreated wastewater. Many live-aboard vessels are permanently
anchored and mobile pumpout facilities are required to service those vessels. There
are no mobile pumpout facilities in the Keys. Overall, live-aboard vessels account
for approximately 2.7% of total nitrogen and 2.9% of total phosphorus loading to
the region's surface waters.
OTHER SOURCES
Nutrients come from a variety of other sources. Loadings to the waters of the
Keys from most other sources, such as Florida Bay, Gulf of Mexico, oceanic
upwelling, and atmospheric deposition have not been quantified. Nutrient inputs
from those sources external to the Keys may be greater than anthropogenic loadings
from wastewater or stormwater emanating from the Keys. However, that does not
diminish the importance of focusing on anthropogenic nutrient loadings and their
effects on water quality and biological resources. Since maintenance. of healthy,
natural communities of the Keys is dependent on low nutrient environments,
localized sources of nutrients can have immediate negative impacts that can result
in cascading effects throughout the ecosystem. Nutrient loadings from atmospheric
sources are diffuse and evenly distributed over the Florida Keys. Wastewater
nutrient loadings emanate from the land-water boundary and may cause
concentration increases in canals and confined nearshore waters well above those
caused from atmospheric or other sources. Similarly, upwelling of deep ocean
waters can provide nutrients, particularly to the outer reef tract and areas seaward of
the Keys. Although the concentration of nutrients in upwelled oceanic waters is
low, the total loading to the reef system can be significant because of the high
volume of water. External advective nutrient inputs are more diffuse than land-
based, human-induced sources. Very little data are available on the physical
processes driving advective and atmospheric loadings and their effects on water
quality of the Florida Keys. This is a topic that requires further research.
Florida Bay has represented a source of nutrient-rich and turbid waters to the
Florida Keys for approximately the last 4,000 years. The discharge of Florida Bay
waters through the major tidal passes between the Keys has arrested development of
the outer reefs near those locations. In 1987, a significant decline of seagrasses
began in Florida Bay. Although the cause of that die-off is still debated, it was
probably related to manipulation of historic delivery of freshwater to the
Everglades. Several very dry years immediately preceded the initiation of the die-
off and salinities in some parts of Florida Bay were approximately twice seawater
13
strength (70 parts per thousand). The dead seagrasses decomposed and their stored
nutrients became available for phytoplankton algae. Also, sediments which the
seagrasses bound with roots and rhizomes became water-borne with wind events
and resulted in highly turbid water. Since corals thrive in clear, low nutrient waters,
the discharge of turbid, nutrient-rich Florida Bay water is probably having a
detrimental effect on coral reef communities seaward of the tidal passes. Cook et
al. (1997) demonstrated that effect by measuring growth of coral transplants in the
discharge from Florida Bay. Corals exposed to Florida Bay water grew slower and
were less dense than corals transplanted to a reference site (Tennessee Reef).
Corals within the influence of Florida Bay water also had a significantly higher
concentration of symbiotic algae in their tissues, presumably in response to the
more turbid conditions. Brand (1997) and others have tracked Florida Bay water
out to the reef tract using chlorophyll concentrations or satellite imagery reflectance
as a fingerprint of the water mass.
Several studies have analyzed sediments, primary producers, and/or
consumers for trace metals and pesticides (Glynn et al., 1989; Manker, 1975;
Skinner and Jaap, 1986; Strom et al., 1992). In general, the results are consistent
with a relatively clean environment with some localized anthropogenic effects. For
example, Strom et al. (1992) found relatively high cadmium at stations near the
Seven Mile Bridge and Newfound Harbor Key. Highest metal concentrations were
found in consumers (sponges) which is indicative ofbioaccumulation.
Marinas have the potential for polluting water or sediments from boat
scraping and painting operations, fueling, and engine repair. Data are not available
to quantify loadings of pollutants from marina operations.
Pesticides are a potential threat to marine life. Chemicals used in mosquito
control are known to be toxic to aquatic crustaceans, such as lobsters, shrimp, and
crabs. Pesticide levels in samples from the Keys have been historically low (Strom
et al., 1992). Although the amounts of pesticides currently used by the Mosquito
Control Program are known, no information is available on the amount of pesticides
that reach marine waters. Also, nothing is known about the environmental
concentrations or effects of residual pesticides in marine waters. That is an area of
research that will be examined in 1998.
Other "natural" sources of pollutants include animal wastes, runoff from
natural environments, and weed wrack. Although bird droppings can be a
14
significant source of nutrients locally, for example around breeding or roosting
islands, they represent a redistribution and recycling of nutrients currently in the
system and are generally not considered pollutants.
Weed wrack consists of detached blades of benthic seagrasses and algae that
become wind-driven into large floating mats. These mats can become trapped
along shorelines and in canal systems along the windward side of the Keys.
Decomposition of the weed wrack removes oxygen from the water, releases
nutrients, and forms toxic hydrogen sulfide gas. With wind shifts, weeds trapped
along shorelines move offshore. However, weed wracks trapped in canal systems
result in the build up of organic debris. Decomposition of organic matter quickly
strips all oxygen from stagnant canal waters. Mobile life forms (e.g., fish) may be
able to leave the canal before succumbing to low oxygen concentrations. Other
relatively non-mobile life forms that require oxygen (e.g., corals, benthic worms
and mollusks) can not survive.
Many nearshore waters are very shallow with bottoms consisting of fine
sediments. Fine sediments can be re-suspended in the water column by
disturbances, such as boat traffic. High use areas are experiencing chronic turbidity
generated by the growing number of recreational and commercial vessels that
transit those waters. Turbid waters could detrimentally affect seagrass (shading)
and adjacent hard bottom communities (smothering). Research and monitoring are
needed to quantify the effects of chronic turbidity on biological communities.
CANALS AND OTHER CONFINED WATERS
There is much variability in the design and physical characteristics of canal
systems in the Keys. Differences in length, depth, slope, geometry, and underlying
geology of canal systems, as well as the population density, affect the impacts of
nutrient loading, flushing rates, and the water quality in the canals. The following
summary of information on water quality findings in canals is based on studies for
particular canal systems. However, many generalities about canal systems can be
gleaned from this information.
Much of the pre-1970 information on canal systems in Florida was
15
summarized by Barada and Partington (1972) who reviewed the literature and
performed a survey of environmental officials. Based on water quality data and the
personal experience of the individuals surveyed, Barada and Partington concluded
that excavating artificial canals causes serious environmental degradation within the
canals themselves and in waters adjacent to canals. Deep, narrow, box-cut canals
with dead-end configurations gradually accumulate oxygen-demanding and toxic
sediments and organic wastes, causing low dissolved oxygen, objectionable odors
(hydrogen sulfide gas), floating sludge, fish kills, and anaerobic and putrid
conditions. Eutrophication of canals with poor circulation is accelerated by a heavy
pollution load which is related to population density and shoreline length. Sources
of pollution into the canals investigated include stormwater runoff, septic tanks,
sewage effluent, and live-aboard houseboats.
Citing Smith, Milo, and Associates (1970), Barada and Partington concluded
that none of the soils in Monroe County are suitable for septic tanks. . The high
water table and extremely porous soils "nullifies the filtering capacity and virtually
raw sewage is leached into the waterways." The report also recommended against
the discharge of effluent from package plants into canals. Package plants with
secondary treatment remove most of the organic material and bacteria, but do not
effectively remove dissolved contaminants, such as phosphates, nitrates, and other
chemicals that contribute significantly to the degradation of water quality.
Chesher (1973) performed an environmental study of canals and quarries in
the lower Keys and concluded that the flow-through canal system at Summerland
Key Cove had excellent water quality. Construction of that canal system was begun
in 1957 and completed in 1971. At the time of Chesher's study, 69 houses were
constructed on the 614-lot subdivision. The total population of the subdivision was
207, which included winter-only residents. All houses utilized septic tanks.
Chesher generally found low levels of nutrients in the canals, relatively high
oxygen, and no evidence of stratification. Mean nitrate concentration was about
0.03 mgll (parts per million) and mean phosphate was 0.06 mgll. Fecal coliform
bacteria ranged from 0 to 37 colonies/l00 mI. The canal system configuration and
orientation prevented any algae or seagrass from accumulating in the canal.
Chesher also observed a diverse and numerous biotic community living in the canal
system, including seagrasses, fish, lobsters, and many other species.
Chesher's results are atypical of other canal studies for a number of reasons.
The Summerland Key Cove canal system was only 11 % developed at the time of
16
sampling. Also, nutrients were measured with a HACH kit which is not as sensitive
as standard analytical methods. There is no indication that oxygen measurements
were made in early morning when daily minimums are expected.
It would be interesting to revisit the Summerland Key Cove canal system
today. Chesher's findings of lush marine life is typical of newly dug canals. Barada
and Partington (1972) reported that it is a common fallacy that finger canals provide
a haven in which fish thrive. That condition may occur in the very early stages after
canal excavation. A typical pattern is that in the first few months of spring, bottom
animals and fish are abundant in newly-dug canals. However, with the advent of
summer and hot weather, dissolved oxygen in deeper waters of the canals drops to
zero, or nearly so. There is heavy mortality of benthic organisms and fish are
absent. When cooler weather returns, benthic animals and fish may recolonize.
But, as dead and decaying organic materials gradually build up in the canal bottom,
the number and diversity of marine creatures declines and eventually there is
virtually no desirable biological production in the canal. Taylor and Saloman
(1968) found very little benthic life and half as many species of fish in a ten year
old, box cut canal near St. Petersburg as in surrounding areas. They concluded that
the accumulation of organic material and low dissolved oxygen in canals has a
permanent adverse affect on fish and other marine life.
In 1972, during the peak of finger fill canal construction in the Keys, the
Florida Department of Pollution Control (FDPC) issued a dredge and fill
moratorium halting all canal construction in the Keys until completion of a study to
assess the effects of canal development on the marine habitats, plants, and animals.
One important reason for that study was the apparent drop in average underwater
visibility at the outer reefs from approximately 175 feet in 1968 to approximately
35 feet in 1973. They found that major turbidity problems persisted up to two years
after the completion of a canal dredging project due to slow settling of very fine
particles. Also, the repopulation by seagrasses in areas dredged for access channels
was very slow; dredged grassbeds showed no signs of new growth after ten years.
Ten canal systems were studied in the FDPC (1973) study. Depressed
dissolved oxygen levels were frequently encountered in all canals. The average
bottom concentration was less than 4.0 mgll (the State standard) and often less than
1.0 mgll. Surface and mid water levels of dissolved oxygen of less than 4.0 mgll
were frequent. Long term conditions of low oxygen concentrations resulted in the
growth of anaerobic bacteria which produce hydrogen sulfide which is toxic to
17
most other organisms. Most canal systems studied had reduced number of animal
species and densities compared to reference sites. At the conclusion of the study,
the moratorium on dredge and fill operations was lifted provided strong
enforcement measures were taken for violators of turbidity and other water quality
parameters. In addition, water exchange and circulation of future canal systems
would be critically examined. The FDER study and its recommendations
effectively stopped construction of additional finger fill canal systems in the Keys.
The U.S. Environmental Protection Agency (EPA) (1975) conducted a study
of finger fill canals in Florida and North Carolina and came to the same conclusions
as the FDPC (1973) study. EPA concluded that poorly designed canals result in
poor flushing, which coupled with a seasonal inflow of freshwater, produced
extensive salinity stratification in the canals. The bottom layer of high salinity
water resulted in stagnation, putrification, and extensive nutrient enrichment of the
water column. Canals greater than four- to five-feet deep regularly experienced
violations of State water quality standards for dissolved oxygen (<4 mgll).
The EPA (1975) compared the water quality of two canals on Big Pine Key
at Doctor's Arm Subdivision. At that time, one of the canals was recently
constructed and undeveloped and the other was sparsely developed with septic tank
systems in Miami Oolite substrate. Even though the canal was sparsely developed,
they found reduced oxygen concentrations, increased biochemical oxygen demand,
and increased fecal coliform bacteria compared to the undeveloped canal. The
water quality in both the developed and undeveloped canals was poorer (higher
nutrients and lower dissolved oxygen) than ambient conditions in a well-flushed
adjacent area, Bogie Channel.
Other canal systems tested during the EP A study were in Punta Gorda,
Florida and several locations in North Carolina. Those systems had greater
nutrient levels in developed canals than the Big Pine site, probably because the
canals systems at those locations were more densely developed. Total nitrogen and
organic carbon were the most salient chemical constituents characterizing water
quality differences between developed and undeveloped canal systems. In nearly
every case, concentrations of those two nutrients were significantly greater in the
developed waterways.
At all canals studied by EPA (1975), a dye tracer was flushed down toilets to
measure the time septic tank leachate reached adjacent waters. At Punta Gorda, the
18
dye appeared in the canal within 25 hours at two sites. In North Carolina, the dye
appeared after 60 hours in one test and 4 hours in a second test. Septic tanks at
those locations were approximately 50 feet from the adjacent canals. Dye
introduced into two septic systems on Big Pine Key did not appear in the canal
within 150 hours, the duration of the study. The reason was thought to be due to a
period of sustained high tides. Septic systems were installed in porous Miami
Oolite which has a high percolation rate (2 minutes per inch). However, during the
time of the dye tracer study, the water surface in the canal was kept high due to
natural tidal amplitude (spring tides) and wind driven waters. During the time
frame of the study at Doctor's Arm Subdivision, the observed high tides were
higher than normal and the low tides were not low enough to effect a hydraulic
gradient that would flush the leachate from the seepage field and disperse it to the
canal. Subsequent to the EPA (1975) study, other studies in the Keys have
demonstrated the rapid transmissivity of Keys substrates to wastewater and the
influence of tides on the movement. Those studies are discussed below.
In 1985, the Florida Department of Environmental Regulation (FDER)
studied the water quality of the waters surrounding the Florida Keys in preparation
for the proposed designation of the waters of the Florida Keys as Outstanding
Florida Waters. That study concluded that the majority of the Florida Keys met the
criteria for designation as Outstanding Florida Waters, but that certain areas,
including canals and the vicinity of the Key West outfall should not be included.
Many of the canal systems tested exhibited low values in dissolved oxygen, high
nutrient values, and violations of the fecal coliform standard. Ranges of some
water quality parameters from canals and other ambient stations are given in Table
2.
Canals and other confined water bodies that demonstrated signs of
eutrophication during the OFW study were listed as "hot spots" in the Phase II
Report of the Water Quality Protection Program (EP A, 1993; Table 6-4). That hot
spot list was revised (Table 5) at an interagency workshop sponsored by the South
Florida Water Management District (April 16, 1996). The revised list includes a
relative priority ranking of the top 19 canal systems and other waters that
demonstrate poor water quality based upon the literature and the collective
experience of participants of the workshop. It also includes a brief description of
potential solutions to the water quality problems for each prioritized hot spot.
Three recommendations were made for all high priority, poorly designed canal
systems: install best available technology (BAT) sewage treatment, collect and treat
19
stormwater runoff, and improve canal circulation. Installation of pumpout facilities
was added to the list of recommended solutions for hot spots that included live-
aboard vessels. Improved circulation to canal systems is an essential component of
restoration because water quality of even undeveloped canals generally deteriorates
due to cumulative, long term loading of fine organic matter (high BOD), salinity
stratification, and long residence time (EPA, 1975). However, construction of
flushing channels or installation of culverts to improve circulation may not be
practicable at all locations due to physical constraints and quantity and quality of
natural resources that would be impacted during or after construction.
The FDER (1987) measured thirty-two water quality parameters at twelve
nearshore sites in Marathon for one year (1984). Primary sampling sites were in
canals and marina basins at Faro Blanco Marina, City Fish Market, Winn Dixie
Shopping Center, Key Colony Beach Sewage Treatment Plant, and the 89th to 91st
Street canal system. High levels of nutrients (0.14 mgll ammonia) and fecal
coliform bacteria (3400 colonies/l00 mI) were found at Faro Blanco Marina during
the tourist season (November to May) due to discharge of raw sewage from live-
aboard vessels. Total Kjeldahl nitrogen, total phosphorus, and biochemical oxygen
demand were
significantly higher in the marina than in adjacent waters.
The 90th Street canal station was selected to monitor leachate from septic
tanks and cesspits. FDER consistently found violations of dissolved oxygen (<4
mgll) at the head of the dead-end canal. With a single exception, mean monthly
fecal coliform bacteria were higher at the end of the canal (3 to 37 colonies/l00 mI)
than mean concentrations at the canal mouth (1 to 6 colonies/l00 mI). Fecal
coliform concentrations were highest during Thanksgiving, Christmas, and New
Year's holiday periods. The maximum reading was 1220 colonies/l00mI.
Orthophosphate (0.04 mg/l) and mean chlorophyll concentrations (29 ugll) were
also significantly higher in the canal than at the reference site, indicating
eutrophication and algal blooms. FDER also found high levels of mercury, lead,
zinc, copper, and hydrocarbons in the canal sediments, presumably from boats.
Iron levels were significantly higher in the canal which is indicative of stormwater
runoff (EPA, 1975).
FDER (1987) measured coprostanol, a degradation product of cholesterol,
which is excreted in human waste. The presence of coprostanol in marine
20
sediments provides a historic record of sewage contamination. Coprostanol levels
at Faro Blanco Marina were 2 to 50 times higher in marina sediments than in
reference sediments. Coprostanol levels (mean = 256; maximum = 1645 ng/g)
were highest in sediments directly below boat slips, indicating that the primary
source of fecal contamination was from discharge of untreated sewage from vessels.
Reference stations averaged 34 ng/g coprostanol.
Concentration of coprostanol at the outfall of the Key Colony Beach sewage
treatment plant (secondary treatment) was 294 ng/g. Of the three locations in which
coprostanol was measured in that study, the area surrounding the Key Colony
Beach outfall was the least impacted by sewage. That is not surprising because
secondary treatment plants remove between 85% and 95% of total suspended solids
(TSS) in raw sewage, and coprostanol is normally associated with TSS.
Coprostanol was found in sediments from the 89th, 90th, and 91 st Street
canals and exhibited spatial and temporal variability. Sediments from the 90th
Street canal contained the highest coprostanol concentrations found in the study
(2206 ng/g). All three canals sampled contained high levels of coprostanol and
were heavily impacted by sewage-derived materials. Mean coprostanol
concentration ranged from a maximum at the head of the 91st Street canal (1363
ng/g) to a minimum at the middle of the 90th Street canal (160 ng/g). In general,
coprostanol levels decreased from the end of each canal toward the canal mouth,
probably reflecting a flushing gradient within each canal. Substantial amounts of
sewage-associated, fine-grained material appeared to be transported out of the
canals by tidal exchange and deposited in the nearshore access channel, where
coprostanol was measured at 681 ng/g. Coprostanol was
undetectable (<10 nglg) in four out of five sampling events at a station located
approximately one mile offshore; at one sampling event, coprostanol was detected
at that reference site in very low concentration (28 ng/g).
FDER (1987) measured water quality in a canal system that received
stormwater drainage from the Marathon Winn Dixie shopping center. An occluded
effluent pipe and inefficient drainage of the parking lot reduced the amount of
stormwater discharged to the canal and the impact of stormwater runoff at that
location could not be definitively evaluated due to the low discharge volume.
Regardless, FDER reported significant gradients in the canal that could be the result
of septic tank seepage and stormwater. Dissolved oxygen levels were significantly
depressed at the head of the canal. Mean monthly levels ranged from 3.06 mgll to
21
4.93 mgll, whereas those at the mouth of the canal fell below 5.0 mgll only once
during the study. On 76% of the days sampled, the dissolved oxygen at the head of
the canal was below the State minimum criterion.
At the Winn Dixie site, monthly concentrations of total nitrogen and
ammonia nitrogen were statistically indistinguishable between canal waters and
ambient waters. However, phosphorus concentrations at the stormwater discharge
site (maximum = 0.04 mgll) were significantly higher than those measured at the
mouth of the canal (0.01 mgll) and offshore (0.01 mgll). Orthophosphate levels
peaked during July and autumn (rainy season) at the canal head and averaged two to
three times above those measured at the canal mouth.
FDER (1990) conducted an intensive, one-year study to assess the water
quality in Boot Key Harbor. Boot Key Harbor has approximately 400 live-aboard
vessels during winter months. Stations were located in canals, the Harbor basin,
and a reference site. Annual mean dissolved oxygen concentrations were lowest in
canals and basin (4.2 mgll) compared to the reference stations (6.1 mgll). Low
dissolved oxygen levels in the canals and basin were due to poor flushing
characteristics that resulted in the canals serving as sinks for organic matter.
Regular violations of the State standard for dissolved oxygen were observed in the
canals.
Fecal coliform bacteria concentrations were highest at canal stations and
were practically absent at reference stations. Highest fecal coliform levels were
observed at stations with on site disposal systems after a heavy rainfall. Fecal
coliform levels in Boot Key Harbor basin stations were highest during winter
months at stations in close proximity to live-aboard vessels. Violations of the State
standard for fecal coliform bacteria were common.
Florida Bay Watch is a volunteer program to collect water quality data in
Florida Bay and the Florida Keys. Bay Watch volunteers take water quality data
that augment ongoing studies by agencies and institutions. Between July 1995 and
June 1996, Bay Watch volunteers sampled 38 fixed nearshore stations, of which 16
were in residential canals, 1 in a boat basin, and 21 at natural shorelines (Florida
Bay Watch, 1996). Immediately apparent is the variability of the data, both at any
station and between stations. This may be due in part to varying climatological
differences between sampling intervals. However, some basic generalities appear
from this data set. Twenty one of the stations had enough data to determine
22
seasonal trends. Of those, 5 of the canal sites had higher nitrogen during the wet
season; others showed no seasonal variation. There were no significant trends
spatially or seasonally of total phosphorus with station location. Highest
chlorophyll levels occurred in bay side canal sites.
In 1997, Bay Watch volunteers sampled 36 fixed nearshore stations for water
quality. Nutrient data varied among stations because of the many differences
between sampling sites, such as flushing rates, density and number of residences,
proximity to injection wells or other discharges, and stormwater controls.
However, these data are very useful in comparing and ranking nearshore waters.
For example, the canal system on Duck Key is very well flushed due to its flow-
through design and proximity to open waters of the Atlantic Ocean. Also, density
of residences is comparatively low on Duck Key. In contrast, The Eden Pines (Big
Pine Key) and Ramrod Key canal systems are long, with many dead-end fingers
and relatively dense development. Differences in water quality parameters from
Duck Key and the Eden Pines and Ramrod Key canals are striking (Table 6). For
example, in 1997 mean total nitrogen was approximately twice as high in Eden
Pines (40.5 uM) and Ramrod (35.8 uM) compared to Duck Key (19.8 uM). Mean
total phosphorus and mean total chlorophyll-a showed similar trends. A natural,
unobstructed shoreline at Grassy Key (bay side )is included in Table 6 for
comparison. These data document the degraded water quality in poorly flushed,
long dead-end canal systems (Baywatch, 1997).
OTHER NEARSHORE WATERS
Because the Florida Keys ecosystem is an "open" system and receives water
from many sources, defining the causes of changes in the community structure
becomes more difficult farther from the shore. Several studies have been
performed to investigate the extent of impacts from land-based nutrient loading to
nearshore habitats.
Lapointe and Clark (1992) measured water quality parameters at 30 stations
during summer and winter to characterize seasonal extremes of measured variables.
Sampling at each site was performed along an onshore-offshore transect. They
found a gradient in nutrients from inshore to offshore. Man-made canal systems
had significantly elevated concentrations of soluble reactive phosphorus (0.3 uM)
compared to seagrass meadows (0.1 uM), patch reefs(0.05 uM), and offshore reef
23
banks (0.05 uM). Ammonia was highest in canal systems and seagrass meadows
(> 1 uM) compared to patch and bank reef stations (<0.3 uM). Chlorophyll and
turbidity were highest in canal systems and seagrass meadows and reached peak
levels during summer months. Chlorophyll was> 1 ugll at canal and <0.3 ugll at
bank reef stations They concluded that widespread use of septic tanks increases the
nutrient contamination of groundwaters that discharge into shallow nearshore
waters, resulting in coastal eutrophication.
Seagrasses and other community components integrate the effects of
nutrients in the water column over time. Growth of benthic algae, increased
chlorophyll (phytoplankton) in the water column, as well as increased nutrient
concentrations have been used to gauge the onset of eutrophication in tropical
marine ecosystems (Bell, 1992). Lapointe et al. (1994) assessed how nutrient
enrichment affects algal growth on seagrass blades (epiphytes), and the productivity
and structure of the shallow water turtlegrass (Thalassia testudinum) community in
the Keys. A stratified-random sampling technique was utilized along three
onshore-offshore transects perpendicular to shore in the Middle and Lower Keys.
Inshore stations (hypereutrophic) were selected in areas receiving direct impacts of
wastewater nutrient discharges, and included a canal mouth with septic tanks and
cesspits (Doctor's Arm Subdivision, Big Pine Key), live-aboard vessels (Houseboat
Row, Key West), and a package sewage treatment plant (Fiesta Key Campground).
Eutrophic and mesotrophic stations were located within approximately 1 km from
land. Oligotrophic stations were located along the back reef at Alligator Reef, Looe
Key, and Sand Key.
Total nitrogen and total phosphorus decreased linearly from inshore stations
to offshore stations. Offshore stations had the highest shoot densities, areal
biomass, and areal production rates, and lowest epiphyte levels. Nearshore seagrass
meadows had greater diversity of primary producers, including macroalgae,
attached seagrass epiphytes, high phytoplankton concentration (green water), and
jellyfish (Cassiopeia spp.) Lapointe et al. (1994) concluded that nutrient-enhanced
productivity of macroalgae and attached epiphytes leads not only to decreased
productivity of turtlegrass, but also may reduce dissolved oxygen levels that results
in significant habitat damage prior to actual die-off. Eutrophic seagrass meadows
in the Florida Keys were found to have pre-dawn hypoxia (<2.0 mgll dissolved
oxygen) or anoxia (<0.1 mgll) during warm, rainy periods. McClanahan (1992)
reported low predawn oxygen concentrations were negatively correlated with
species richness and diversity of mollusks in Florida Bay compared to waters with
24
higher oxygen found offshore Key Largo. Lapointe et al. (1994) found that at
concentrations of approximately 25 uM nitrogen and 0.45 uM phosphorus,
turtlegrass is replaced by shoalgrass (Halodule wrightii), an opportunistic seagrass.
They concluded that nutrient enrichment from land-based sewage inputs can have
significant effects on seagrass productivity for considerable distances from shore.
OUTER CORAL REEFS
Szmant and Forrester (1996) measured distribution patterns of nutrients to
determine whether anthropogenic nutrients from land-based sources may be
reaching the outer reef tract. Samples were collected along seven transects oriented
perpendicular to the shoreline and located from Biscayne National Park to Looe
Key. Samples were taken along transects at stations located in tidal passes and
canal mouths to approximately 0.5 km seaward of the outermost reef. Water
column and sediment concentrations of nitrogen and phosphorus were measured.
In the Upper Keys, water column nitrogen (1 um N03) and chlorophyll (1
ugll chi a) were elevated near marinas and canals, but returned to oligotrophic
concentrations within 0.5 km of shore. Phosphorus concentrations were higher at
offshore stations (>0.2 uM P04) and were attributed to upwelling of deep water
along the shelf edge at the time of sampling. Sediment interstitial nitrogen
concentrations decreased from inshore to offshore stations which is indicative of an
onshore source of nitrogen. There was some indication of a reverse trend for
phosphorus that may be indicative of upwelling of deep oceanic waters as a source.
In the Middle Keys, both water column nutrients and chlorophyll
concentrations were higher than observed in the Upper Keys, and there was less of
an inshore-offshore gradient than noted in the Upper Keys. Sediment nutrients
were also higher, and there were no differences in nutrient concentrations at
nearshore and offshore areas. These observations may be explained by the mixing
of Florida Bay waters with the waters adjacent to the Keys.
These data support the conclusion that outer reef areas in the Upper Keys are
not accumulating elevated loads of land-derived nutrients via surface water flow,
but do document moderately elevated nutrient and chlorophyll levels in many
developed nearshore areas. The authors concluded that most of the anthropogenic
25
and natural nutrients entering the coastal waters from shore appear to be taken up
by nearshore algal and seagrass communities before they reach patch reef areas
(about 0.5 to 1 km from shore). Further work is needed to determine whether
nutrient-enriched groundwaters reach the reefs, however these would be expected to
cause an enrichment of reef sediments, which was not observed.
Lapointe and Matzie (1996) used high frequency sampling to track effects of
periodic rainfall events on a transect that included stations in a canal on Big Pine
Key (Port Pine Heights), a seagrass meadow (Pine Channel), a patch reef
(Newfound Harbor), and an offshore reef (Looe Key). Lowest dissolved oxygen
(<0.1 mgll), maximum concentration of N~ +, total dissolved phosphorus, and
chlorophyll, and minimum salinities were measured in the canal during a rain event.
Concentrations of total dissolved phosphorus also increased at the seagrass, patch
reef, and offshore reef stations after the initial rainfall event. Concentrations of
NH4 + and chlorophyll increased at offshore stations approximately 1 to 3 weeks
following the rain event. The authors suggested that rainfall events can rapidly
flush nutrients into canals and adjacent nearshore waters. These nutrients may have
the potential of impacting water quality for considerable distances from land;
however, more research is required to substantiate these findings and define the
area of impact. Lapointe and Matzie (1996) concluded that the effects of increased
concentrations of nutrients in nearshore waters justifies that special precautions be
taken in the treatment and discharge of wastewaters and stormwater runoff.
Lapointe and Matzie (1997) measured water quality parameters along a
transect from the eastern shoreline of Big Pine Key to Looe Key from January to
October 1996. The inshore station was located off Avenue J Canal and was down
gradient of approximately 1,000 septic tanks and cesspits. A patch reef station was
located off Munson Island, and an offshore station was located along the back reef
at Looe Key. Monthly samples were taken, along with high frequency sampling
prior to, during, and following selected rainfall and wind events. Lapointe and
Matzie also measured nitrogen isotope ratios in macro algae and seagrass blades to
determine the source of the nitrogen; there is a higher ratio of 15N/4N in
wastewater.
Highest levels of dissolved inorganic nitrogen, soluble reactive phosphorus,
and chlorophyll occurred during periods of high winds, low tides, and rain events.
The highest nitrogen and phosphorus concentrations were measured at the inshore
26
station at low tide when tidal ranges were highest. Low tides allow rapid drainage
of nutrient enriched groundwater to adjacent surface waters.
Ratios of nitrogen isotopes were highest in a benthic algae at the nearshore
station (5.0 0/00), intermediate at the patch reef station (3.5 0/00), and lowest at
Looe Key (3.0 0/00). These data may indicate increasing wastewater nitrogen
contributions to algae with increasing proximity to shore. However, because there
are many sources of nitrogen, only one isotopic indicator was used in that study,
and there may be more denitrification inshore than offshore, additional research is
required to quantitatively define the sources of nitrogen.
Lapointe and Matzie (1997) observed that a large area of seagrasses located
near the mouth of the A venue J Canal was covered by a heavy growth of attached
and benthic algae and that approximately 2.5 acres of seagrasses had been replaced
by benthic algae at that location. They also documented blooms of benthic algae
and epiphytes on seagrass blades at Looe Key.
It is very difficult to quantify all sources of nutrients and their effects at
offshore areas. For example, there is no quantitative information available on the
impacts of increased numbers of charter boats or other vessels that flush their heads
and holding tanks at offshore areas. Reduction of predators and grazers is another
confounding factor affecting the community composition of the outer reef.
Preparation of a detailed nutrient budget for nearshore and offshore areas in the
Florida Keys is a topic that requires further research.
GROUNDWATER
Information on the geology and hydrogeology of the Florida Keys is
summarized by Halley et al. (1997). Several studies have been performed that
demonstrate the transmissivity of the substrates of the Florida Keys and the rapid
exchange of wastewater from onsite systems or injection wells to surface waters.
Lapointe et al. (1990) measured significant nutrient enrichment of
ground waters contiguous to on site disposal systems at several sites. Mean
dissolved inorganic nitrogen (987 uM) was 400 times higher and mean soluble
reactive phosphorus (9.77 uM) was 70 times higher in groundwater adjacent to a
27
septic tank seepage field compared to a reference site. Concentrations of nitrogen
and phosphorus decreased in the groundwater away from the septic tank toward the
adjacent canal, presumably due to dilution by groundwater. They also theorized
that some of the soluble reactive phosphorus was absorbed by the substrate.
Concentrations of nutrients in the canals (dissolved inorganic nitrogen 4.91 uM;
soluble reactive phosphate 0.43 uM) were elevated compared to control sites.
Concentrations of nutrients in the canals were highest in the summer because of
seasonally maximum tidal ranges and increased flushing during the summer wet
season. Lapointe et al. (1990) used a groundwater flowmeter to demonstrate that
lateral rates of shallow groundwater flow increased by approximately three times
during ebbing tides as compared to flooding tides. This observation was supported
by Lapointe and Matzie (1997) who found the maximum concentration of dissolved
inorganic nitrogen off the Avenue J Canal (Big Pine Key) when tidal ranges were
the highest during the study period.
Shinn et al. (1994b) placed and sampled 24 wells beneath the Keys,
nearshore areas, and outer reefs to determine if sewage effluent from Class V wells
is reaching offshore reef areas via underground flow. Class V wells (drilled 90 feet
and cased to 60 feet) are currently permitted by the Florida Department of
Environmental Protection (FDEP) for disposal of wastewater. Sample wells were
located in transects off Ocean Reef Club, Key Largo, and Saddlebunch Keys and
were sampled quarterly for one year. Investigators found well water to be
consistently hypersaline with a marked increase in ammonia in offshore
groundwater. Other forms of nitrogen and phosphorus present in offshore
groundwater were only slightly elevated above levels found in surface marine
waters. Highest levels of nitrate, nitrite, and phosphorus were found in shallow
onshore groundwaters.
N earshore wells were observed to discharge water during falling tides and
draw water into the wells during rising tides. This "tidal pumping" results in
considerable water movement in and out of the upper few meters of limestone and
is a likely mechanism for mixing and transferring nutrient-rich groundwater into
overlying surface waters.
Gene Shinn (personal communication) described Key Largo limestone as
having a consistency of Swiss cheese, and several other studies have confirmed the
rapid connection of groundwaters with surface waters in the Key Largo limestone
matrix.. Paul et al. (1995a) placed a man-made tracer virus in a septic tank and into
28
a 13.7 m (45 ft) deep injection well in Key Largo and found the virus in the surface
waters of an adjacent canal and the Atlantic Ocean in 11 and 23 hours respectively.
Rates of migration ranged from 0.57 to 24.2 mIhr (1.87 to 79.3 ftlhr). They
concluded that current on site disposal practices in the Florida Keys can lead to
rapid nutrient enrichment and fecal contamination of subsurface and surface marine
water in the Keys. Viral tracers were detected on falling tides confmning the
findings of tidal pumping by Shinn et al. (1994b), Lapointe et al. (1990), and
Lapointe and Matzie (1997).
Paul et al. (1997) repeated the viral tracer experiment with 12.2 m (40 ft)
deep injection wells on Key Largo and a permitted 27.4 m (90 ft) deep Class V
injection well on Long Key. At both sites, viral tracers appeared in the
groundwater within 8 hours after injection, and in marine surface waters 10 hours in
Key Largo and 53 hours in Long Key.
Chanton et al. (1998) are using natural tracers to locate areas of groundwater
discharge to surface waters surrounding the Florida Keys. They are also using
artificial tracers to quantify rates of flow of materials injected into groundwater to
surface waters.
Chanton et al. have completed two extensive surveys and have mapped areas
of concentrations of natural tracers near the Keys. Groundwater seepage areas have
been found on both the Florida Bay and Atlantic Ocean sides of the Keys. Two
injection studies have been completed, one on Key Largo and one on Long Key. In
both tests, the tracer was injected into groundwaters and was observed, greatly
diluted (approximately one million times), within hours to days in nearby surface
waters. At the Long Key site it was found in a canal located across U.S. 1 from the
injection site. Wastewater injected into the groundwater at Long Key rapidly
migrated toward the surface due to the fact that freshwater "floats" on the highly
saline groundwater.
Kump (1998) has sampled groundwater in wells drilled to various depths
surrounding a wastewater injection well on Long Key. He confirms the presence of
a shallow, low salinity lens floating on top of groundwaters. Distribution of
nutrients away from the site of injection is variable, but phosphate, nitrate, and
ammonia concentration appears to be highest nearest the injection well at a depth of
5 meters. However, the elevated concentrations of these nutrients were observed in
sampling wells located in different directions from the point of injection. The
29
absence of phosphate in high pH waters in shallow wells leads to the postulation
that phosphate may be removed by adsorption onto the limestone substrate.
In October 1996, Kump injected phosphate at the same time that Chanton et
al. injected a non-reactive tracer (sulfur hexafloride- SF6) into a Class V injection
well (60/90 feet) at Long Key. Within four hours there were elevated tracers at the
sampling well located between the injection well and the Atlantic Ocean. The peak
of both tracers occurred after about 3 hours. After the peak, the ratio of the tracers
fell because the concentration of P04 fell more rapidly than that of SF6. Using data
from one of the sampling wells, it was calculated that the tracer SF6 appears to be
moving vertically at about 7 m1day. The pattern of early SF6 peaks in some wells
that are associated with phosphate peaks, and later SF6 increases with no increase in
phosphate concentration at other wells, cannot be ascribed simply to dilution of
phosphate by groundwater. The predicted phosphate concentrations based on the
assumption of no preferential uptake and the observed tracer concentrations would
be well above detection at many of the wells. These observations support the
hypothesis that phosphate is being stripped from the groundwater. The rate and
long term capacity of substrates in stripping phosphate are topics that require
additional research.
FECAL COLIFORM BACTERIA AND DISEASE ORGANISMS
In addition to nutrient enrichment of subsurface and surface waters, on site
disposal systems and injection wells are known to be a source of microbial
contamination of groundwater (Keswick, 1984). Because the groundwaters and
surface waters are very closely linked in the Keys, it is not surprising that fecal
coliform bacteria are common in canals and boat basins. As discussed above, fecal
coliform violations were common in some studies (FDER, 1987, 1990). To date,
there has not been a systematic public health survey of canals and other confined
waters of the Keys to determine their risk to human health. That is a topic that is
currently undergoing study.
Paul et al. (1993) sampled the occurrence of viruses and bacteria in the
vicinity of Key Largo. Water column viral counts were highest in Blackwater
Sound, decreased to the shelf break, and lower salinity waters had higher numbers
of viruses. Viral counts in sediments averaged nearly 100 times those found in the
water column and did not correlate with salinity. They concluded that viruses are
30
abundant in the Key Largo environment, particularly on the Florida Bay side, and
that processes governing their distribution in the water column are independent of
those governing their distribution in sediments.
Shinn et al. (1994b) found fecal coliform and fecal Streptococci bacteria in
several of their wells. At the Saddlebunch transect, they found that the inshore well
and the wells farthest from the shore (>2 nm) tested positive for fecal coliform
bacteria during several rounds of testing. The investigators speculated that the
source of the bacteria in the well on shore may be from septic tank drainfields at a
recreation vehicle park on Saddlebunch Key. The source of the bacteria in the
offshore wells is unknown because the locations of the wells are remote from areas
of large human populations. The authors speculated that contamination of the more
offshore wells could be the result of rapid flow through the underlying Key Largo
limestone from a remote site, such as Marathon, where there is a large community
built on Key Largo limestone. The investigators theorized that if the bacteria are
not some unknown, anoxic, non-fecal, non-human form indigenous to hypersaline
groundwater, then their presence suggests a land source and considerable offshore
groundwater movement.
In Key Largo, Shinn et al. (1994b) found fecal coliform and Streptococci
bacteria consistently in the shallow well and once in a deep well on the island. The
shallow well was within 50 ft of a septic tank drainfield. At Ocean Reef Club, the
shallow onshore well also had fecal bacteria during all four sampling rounds. Fecal
bacteria were also found in offshore wells, including a well located approximately 5
nm offshore.
Supporting evidence of nearshore contamination by fecal bacteria is provided
by Paul et al. (1995b). They found two or all three fecal indicators for which they
tested (fecal coliform, Clostridium perfringens, and Enterococci) in onshore
shallow (1.8 to 3.7 m; 6 to 12 ft deep) monitoring wells at Key Largo. Deep wells
(10.7 to 12.2-m; 35 to 40 ft deep) at the same sites contained few or no fecal
bacteria. Fecal indicators were found in two of five nearshore wells that were 1.8
and 2.9 miles from shore. Wells further offshore showed little signs of
contaminations. All indicators were also found in surface waters in a canal in Key
Largo and in offshore surface waters in March, but not in August. These results
suggest that fecal contamination has occurred in the shallow onshore aquifer, parts
of the nearshore aquifer, and certain surface waters. Paul et al. (1995) concluded
31
that current sewage waste disposal practices may have contributed to the observed
contamination.
Finally, Griffen et al. (1997) have found fecal coliform, E. coli, and
Clostridium at most stations sampled in Boot Key Harbor on June 8-13, 1997.
EFFECTS ON BIOLOGICAL COMMUNITIES
Nutrient-rich, land-based sources of pollution from runoff and wastewater
disposal practices in the Keys rapidly gets into surface waters. Data on nutrient
enrichment in canals is compelling. Several investigators observed that canals were
depauperate in marine life (Taylor and Saloman, 1968; Barada and Partington,
1972; EPA, 1975) and fish kills in residential canals are common (Taylor and
Saloman, 1968; Barada and Partington, 1972). Seagrasses, which are common in
shallow waters around the Keys, are generally absent or reduced in density in
stagnant canals because of canal depths and/or periodically high phytoplankton
blooms, turbidity, and hydrogen sulfide gas (EPA, 1975). Lapointe et al. (1994)
observed a shift in community structure in an enriched canal and that the seagrass
meadows adjacent to the mouth of the canal was eutrophic, as demonstrated by lush
macroalgae growth, high epiphyte load on seagrass blades, and high phytoplankton
(chlorophyll) concentration. A large area of seagrasses was stressed and
approximately 2.5 acres of seagrasses were replaced by benthic algae at the mouth
of the Avenue J Canal (Lapointe and Matzie, 1997). Waters in Boot Key Harbor
and adjacent canals had high nutrient and chlorophyll concentrations (FDER, 1987,
1990).
It would be beneficial, but costly, to have long term water quality data from
all canal systems and harbors in the Keys. However, there is no reason to believe
that other dead end canals systems, enclosed marinas, and harbors are radically
different from the ones that have been studied.
There are natural gradients in community structure related to depth, current
flow, sediment types, and other environmental conditions. The marine life in many
confined water bodies and some nearshore areas are dissimilar, structurally and
functionally, to natural communities found in less disturbed, more oligotrophic
waters. The causes of these differences are differences in physical conditions (e.g.,
circulation, temperature) and nutrient enrichment (eutrophication). Based on
32
available information, it is reasonable to conclude that poorly flushed canals, other
confined water bodies, and nearshore areas in the Keys have reached and exceeded
their assimilative capacity for nutrient addition. If nutrient loading continues,
impacted areas will become increasingly dysfunctional and the impacts will extend
further from shore.
Previous sections have summarized scientific information that demonstrated
the effects of human-derived pollutants on marine waters. Perhaps even more
compelling than the scientific data is the general acknowledgment by long-time
residents and visitors that water quality has declined in the Florida Keys. Although
long term climatic cycles can not be completely excluded, there is abundant, albeit
anecdotal, evidence that deteriorating environmental conditions in the Keys are
correlated with increased population and human activities. DeMaria (1996)
interviewed 75 individuals who have spent many years on the waters surrounding
the Florida Keys. These individuals were asked to identify changes in fisheries,
seagrass, communities, the coral reef, algae blooms, and water quality. Each person
interviewed was asked to comment on the most significant changes that they
observed. The results included the following conclusions:
Water quality has declined, particularly in canals, nearshore areas,
Florida Bay, and the coral reefs.
Algal blooms are larger, more frequent, and more persistent.
Seagrass beds have fluctuated in extent and species composition
throughout the area and have drastically declined in Florida Bay.
Corals and coral reefs show signs of declining health; disease is more
common and benthic algae have increased in abundance and spatial
coverage.
Populations of sponges, giant anemones, long-spine sea urchins, and
queen conchs have declined in nearshore waters. Jellyfish have
increased in abundance.
Tropical fish, specifically butterfly fish, angel fish, and groupers have
declined.
33
With very few exceptions, DeMaria (1996) reported that long term Keys residents
observed changes for the worse.
More research is required before definitive statements can be made on the
long term health of the Florida Keys reef tract and the extent and effects of
anthropogenic nutrients. Szmant and Forrester (1996) reported that reefs off Key
Largo and Long Key are not receiving a nutrient subsidy via surface waters from
land-based sources at the present time, although the potential exists due to observed
higher nutrient concentrations near shore. It is their opinion that land-based
nutrients are absorbed by algae and seagrasses within 0.5 km of shore.
Lapointe and Clark (1992), Lapointe and Matzie (1996), and Lapointe and
Matzie (1997) concluded that nutrient enrichment at offshore reefs is possible
following heavy rains and/or high wind events. It is their opinion that sampling
during storms is required to document rapid, episodic transport of nutrients.
However, if land based nutrient subsidy to the reef is common, Szmant and
Forrester (1996) theorized that reef sediments should have elevated nutrient
concentrations. Their findings demonstrated that nutrient concentrations in
sediments decreased rapidly from the shore.
Upwelling of deep, relatively nutrient-rich oceanic water may be a source of
nutrients to the outer reefs. Szmant and Forrester (1996) concluded that upwelling
was probably responsible for elevated phosphorus observed in offshore waters in
the Upper Keys. Upwelling events have also been reported at Looe Key during
spring and summer and may be a source of nitrogen to at least the fore reef
(Lapointe and Smith, 1987). However, coral reefs generally do not develop in areas
influenced by persistent upwelling due to the cold temperatures and high nutrient
content (Dubinsky and Stambler, 1987). The frequency, duration, geographic
extent, and nutrient loading of upwelling events is an area that requires further
study.
Worldwide, there has been a marked acceleration of the deterioration of coral
reefs. Wilkinson (1993, 1996) estimated that 30% of all coral reefs have reached
the "no-return" critical stage, another 30% are seriously threatened, and less than
40% are stable. The main factors in the demise of coral reefs are human pressures,
such as over fishing, physical damage, nutrient enrichment, and sediment loading.
Since there does not seem to be any measurable global-scale increase in oceanic
productivity, which would have been evident in the case of significant overall
34
eutrophication, Dubinsky and Stambler (1996) concluded that human impacts on
coral reefs are on a local and regional scale, rather than a global scale (excluding
impacts of global warming and increases in ultraviolet light exposure).
Long term, quantitative studies of coral reef community structure in south
Florida have documented high coral loss rates. Porter and Meier (1992) monitored
six coral reef locations between Miami and Key West in 1984 and 1991. They
found that all six areas lost coral species and that these losses constituted between
13% and 29% of their species richness. Coral cover decreased at five of the six
sites and net losses ranged between 7.3% and 43.9%. Porter and Meier (1992)
concluded that loss rates of this magnitude cannot be sustained for protracted
periods if the coral community is to persist in a configuration resembling historical
coral reef community structure in the Florida Keys. Porter et al.(1994) suggested
that regional patterns of decline are suggestive of large scale flow of water masses,
e.g. influence of Florida Bay of Gulf of Mexico waters.
A variety of diseases have caused coral decline and mortality (Antonius,
1981a, b; Peters, 1984; Santavy and Peters, 1997). These diseases have been
reported worldwide from pristine as well as heavily polluted areas. Recent
systematic monitoring in the Keys has revealed that the incidence of coral diseases
may be increasing. Disease decimated the long-spine urchin populations
throughout the Caribbean during 1983-1984. Determining the etiology and
distribution patterns of these diseases are topics for future research and monitoring.
Mass mortalities of sea fans have been reported throughout the Caribbean for
many years. The causative agent of sea fan mass mortalities has been determined to
be a fungal pathogen (Aspergillus) that is typically a soil inhabitant. It is thought
that the primary infection by the fungus is probably associated with sediment
particles from land-based sources (runoff) (Smith et al., 1996).
Bell (1992) critically reviewed case studies of eutrophication of coral reefs
and noted that eutrophication typically causes phase shifts from slow-growing
corals to faster growing macroalgae and phytoplankton. Macroalgal blooms have
been correlated with nutrient enrichment of reefs in Jamaica (Lapointe, 1997;
Lapointe et al., 1997), the southeast coast of Florida (Lapointe and Hanisak, 1997),
Belize (Lapointe, et al., 1993), and the inner Great Barrier Reef Lagoon, Australia
(Bell and Elmtri, 1996). Others have pointed out that over fishing and reduction of
35
algal grazers must be taken into account (Zieman and Szmant, personal
communication) .
The impacts of nutrient enrichment to coral reefs are not always clear cut or
devastating to the coral community. Nutrient enrichment studies performed at One
Tree Island, Southern Great
Barrier Reef demonstrated that daily additions of both nitrogen and phosphorus to a
single patch reef for eight months enhanced community primary production by
approximately 25% and inhibited calcification of the system by approximately 50%
(Kinsey, 1988). An extensive nutrient enrichment experiment (ENCORE:
Enrichment of Nutrients on a Coral Reef Experiment) (Larkum and Steven, 1994)
was performed on the Australian Great Barrier Reef to quantify the response of the
community to nutrient additions. Larkum and Koop (1996) found that fertilization
had no effect on growth or primary production of epilithic algae; these results are
contrary to the widely held opinion that enhanced levels of nutrients cause rapid
growth of algae and problems for associated biota.
EXAMPLES OF AREAS WITH SIMILAR PROBLEMS
This section is not meant to be a comprehensive analysis of coastal
eutrophication, but rather to highlight several other areas that have experienced
nutrient enrichment that are reminiscent of observations in the Florida Keys. It is
hoped that we can learn from the actions taken in other locations to correct nutrient
enrichment problems. In several instances, providing additional treatment of
wastewater resulted in rapid improvement of degraded biological communities.
Coastal eutrophication is a national and worldwide problem (Valiela et al.,
1992). It is most evident in enclosed and semi-enclosed seas and estuaries and the
main sources of nutrient enrichment are agriculture and urban run-off and domestic
wastewater (Nixon, 1990; 1995). It is estimated that the input of nutrients to the
coastal waters and oceans from human sources (via rivers) is currently equal to or
greater than natural input (Windom, 1992). Some prominent examples of collapses
of coastal ecosystems from anthropogenic nutrient loading include the loss of
seagrasses and benthic fauna in the Chesapeake Bay (Officer et al., 1984), noxious
algal blooms in the Adriatic Sea (Justic, 1987), anoxia problems in the Baltic Sea
(Larsson et al. 1985) and off the Mississippi River delta (Gulf of Mexico) (Rabalais
36
et aI., 1996; Turner and Rabalais, 1994), and regular toxic algal blooms in the North
Sea (Underdal et aI., 1989).
AUSTRALIA
Australian coastal waters in the vicinity of the Great Barrier Reef are
naturally nutrient poor. All coastal water bodies with long residence times (poor
flushing) in the populated part of the Australian coast have experienced some
measurable
effects of enhanced eutrophication. Phytoplankton blooms and seagrass losses are
the most prominent evidences of nutrient loading (Brodie, 1994). As is true in the
Florida Keys, the farther offshore, the more difficult it becomes to link community
changes with land-based sources of nutrients. However Bell (1991, 1992) and
Brodie (1995) have proposed that the Great Barrier Reef is showing evidence of
eutrophication, as evidenced by an increase between historic and current levels of
phytoplankton.
The Australian government is sponsoring a nationally coordinated approach
to monitoring and managing sources of nutrient enrichment (National Water
Quality Management Strategy). The goals and objectives of the Australian Strategy
are very similar to those in the Water Quality Protection Program for the Florida
Keys. In Sydney, inadequate sewage treatment has resulted in significant
degradation of nearshore waters. Improvements to the sewage treatment system is
being partially financed through a household levy of $80/year (Brodie, 1994).
ST. LUCIE COUNTY
Over the past 50 years, seagrass coverage in the Indian River Lagoon
declined overall about 6%. However large losses (60%) occurred in the Melbourne
to Grant area (Woodward-Clyde Consultants, Inc. (1994). The Indian River
National Estuary Program concluded that seagrass losses were predominantly due
to nutrient enrichment from domestic wastewater and stormwater discharges (EP A,
1996) .
In 1993, St. Lucie County completed a S.W.I.M. Program (Surface Water
Improvement and Management Act) project to identify areas where existing onsite
sewage disposal systems were a threat to the water quality of the Indian River
Lagoon. Ten high priority areas were identified based upon their pollutant loads.
37
Principal recommendations of the S.W.I.M. study included (Moses and Anderson,
1993):
1. Port St. Lucie should be considered a threat to the water quality of
the Indian River Lagoon by way of the C-24 Canal and North Fork of the St.
Lucie River. Expansion and improvement of sewage treatment facilities in
this area should be pursued aggressively.
2. The entire County must be regarded as a single environmental area with
respect to water and wastewater policies regarding effects of septic tanks and
reducing potential for water degradation.
3. Establish a full time county position responsible for identifying and
procuring funding sources for program implementation.
In 1990, the State of Florida Legislature passed the Indian River Lagoon Act
which required all domestic wastewater treatment facilities to cease discharges into
the Lagoon by 1996. It is estimated that implementation of the Act resulted ina
60% reduction of nutrients entering the northern half of Indian River Lagoon. In
the past year, seagrass beds at six fixed transects in the Vero Beach area have
extended in length an average of approximately 260 feet past previous seagrass bed
limits. In the Melbourne area, seagrass beds at seven transects have extended an
average of 195 feet (Vemstein and Morris, Indian River National Estuary Program,
personal communication).
TAMPA BAY
Between 1950 and 1982, seagrass coverage in Tampa Bay declined from
approximately 40,000 acres to 21,600 acres. Associated with the seagrass loss were
declines in commercial and recreation ally important fishes. Three factors were
believed responsible for the decline: dredging and filling of seagrass beds for
residential, commercial, and port development; shading by algae, both
phytoplankton and macroalgae, which bloomed in response to excessive nutrient
inputs from sewage treatment plants and industrial discharges; and turbidity
induced by dredging the main shipping canal. In 1987, the Florida Legislature
passed the Grizzle-Figg Bill which required that all discharges into Tampa Bay
meet strict nutrient guidelines (advanced wastewater treatment). Also, in 1984, the
Legislature established a Bay study group which, in 1985, resulted in the formation
of the Agency on Bay Management. The Agency on Bay Management has become
a vigilant guardian of Tampa Bay. From 1982 to 1992, seagrass coverage increased
38
by about 4000 acres (18.5%). Most "new" grass has been shoalgrass (Halodule
wrightii), an early colonizer which may eventually be replaced in many areas by
turtlegrass. Increase in seagrass coverage has been attributed to the substantial
reduction in nitrogen loadings to the Bay. Reduction in nitrogen has allowed more
light to penetrate deeper into the water column, thus allowing seagrass to
reestablish itself.
OPTIONS FOR CORRECTING WASTEWATER PROBLEMS
ONSITE DISPOSAL SYSTEMS
During the early development of the Keys, human wastes were disposed
directly on the ground, into shallow holes, or in the water. Since there was a very
small population of humans, the ecosystem absorbed these additional nutrients with
little or no change to ecosystem structure or function. During the "period of rapid
growth" in the Keys, cesspits were constructed under or immediately adjacent to
residences and commercial establishments. Cesspits average approximately 4- to 5-
feet deep and may be supported with timbers or stacked cement blocks. Cesspits
are directly connected to groundwater, adjacent canals, or other surface waters
through the porous limerock substrate. Because of the limited amount of land in
the Keys, developments are generally crowded, and many early developments
featured 50-foot by 50-foot lot sizes. That circumstance not only maximized the
development of many areas, but also provided a concentrated source of nutrient
enrichment of groundwater and surface waters. Cesspits provide no treatment of
wastewater nutrients. They also do not provide any confinement or treatment of
human fecal pathogens. The Florida Department of Health estimates that there are
currently approximately 4,000 cesspits in the Florida Keys (Jack Teague, personal
communication).
In the mid 1960's, there was a gradual shift to the use of septic systems for
onsite waste disposal. This shift was prompted by the newly formed State Board of
Health which recognized that use of cesspits was a public health concern. Septic
systems consist of a concrete or fiberglass tank designed to hold waste material
anaerobically. Some nutrients are removed through the production of biomass
which settles in the tank. The accumulated organic sludge must be pumped
periodically and disposed. Pumped sludge is currently disposed by transporting it
to Dade County, where it is added to the wastewater entering sewage treatment
plants. Liquid wastewater effluent exits from the outlet of the septic tank and is
39
distributed to the surface substrate (drainfield). Ideally, the drainfield is composed
of soils with cation exchange sites that trap and hold chemical nutrients.
Unfortunately in the Florida Keys, the substrate is predominantly porous limestone
and has few bonding sites for nutrients other than phosphorus, and the long-term
capability of limestone to trap phosphorus is not known. Thus, in the Keys,
wastewater from septic systems can rapidly seep into the groundwater with little
nitrogen removal. Removal of nutrients by septic systems can vary greatly because
of design, installation methods, and operation, but on the average septic systems
remove approximately 4% of nitrogen and 15% of phosphorus (Table 7). Location
of septic tanks near surface waters, as in closely spaced canal developments,
represents a significant source of nutrient-rich wastewater to surface waters. Rain
events and low tides can result in the rapid movement of septic tank effluent into
surface waters. There are approximately
25,000 parcels in the Keys with on site disposal systems. Of those, 18,000 are
permitted septic tank systems. There are approximately 7,900 lots with no record of
sewage disposal method (Jack Teague, personal communication).
Since 1992, the State Department of Health has required that septic tank
drainfields be underlined by 12 inches of clean sand. This requirement has little
impact on nutrient removal in the effluent, but may trap some pathogens by
filtration through the sand bed.
Since the elevations of the Keys are very close to sea level, the groundwater
is very close to the surface. The ground level of most dredge and fill subdivisions
is only three to four feet above sea level. On most keys, the groundwater is as salty
as seawater. The groundwater responds to tidal action that connects it with Florida
Bay and the Atlantic Ocean. The net movement of groundwater is toward the
Atlantic Ocean (Shinn et al., 1994b).
Septic tanks are installed underground and during installation they can float
in areas where groundwater is high. Many of the early installed septic tanks had
holes punched in their bottoms to sink them in the groundwater before they were
covered over with fill material. Because of that practice, many septic systems
function as cesspits, where wastewater is in direct contact with groundwater
without settlement or treatment.
Chapter 381.0065(4)(k) of Florida Statutes currently mandates that the
Florida Department of Health (FDOH) permit only on site systems capable of
40
meeting Advanced Waste Treatment (A WT) standards. A WT is defined in Section
403.086 of the Florida Statutes as 5 mgll CBODs, 5 mgll total suspended solids
(turbidity), 3 mgll nitrogen, and 1 mgll phosphorus. In order to remove nutrients to
those levels, additional processes must be incorporated into the treatment process.
In the nitrification/denitrification process, ammonia is first converted to nitrate
(aerobically) and then nitrate is converted to nitrogen gas (anaerobically) and
released to the atmosphere. Phosphorus can be removed either biologically or
chemically. In either case, excess phosphorus is removed from the effluent stream
through settling and subsequent disposal of the solids.
Ayres and Associates, Inc., under contract to FDOH, is field testing five
onsite systems at a test facility on Big Pine Key. This research has been recently
funded through 1998. Pending the results of that research, the Florida Department
of Health (FDOH) has been permitting onsite systems which meet current best
available technology (BAT). FDOH has determined that aerobic onsite treatment
systems which discharge to either a bore hole or a drainfield currently meet BAT.
There is a wide variety of designs of onsite aerobic treatment systems, but in
general they are a small scale version of a conventional secondary treatment plant.
Some nutrients are removed through the growth of bacterial biomass and
subsequent disposal of biosolids. Operation and maintenance is critical to the
efficient performance of aerobic systems. Aerobic systems are much more efficient
than septic tanks in removal of carbon (77%), but are only slightly better than septic
systems in removing nitrogen (Table 7).
There are currently no A WT treatment facilities in the Florida Keys. By
State statute, advanced wastewater treatment facilities are required in two locations
in Florida, Tampa Bay and Indian River Lagoon. The statutes were enacted to
address eutrophication of those waters due to excess nutrient loading and to reverse
the pending collapse of the ecosystems.
PACKAGE PLANTS
During the early development of the Keys, multifamily dwellings, motels,
and resorts utilized cesspits and septic tank systems. Florida Administrative Code
(F.A.C.) Rule 62-620.100 currently requires a valid permit from the FDEP for
construction and operation of domestic wastewater facilities with flows exceeding
10,000 gpd and for commercial establishments with wastewater flows greater than
5,000 gpd.
41
At the present time there are 250 FDEP-permitted wastewater treatment
plants (WWTP) in operation in Monroe County. There are approximately 14
additional FDEP wastewater permits that have been issued for new WWTP that
have not yet been constructed. Most of these WWTP consist of on-site facilities
with permitted flows under 100,000 gpd and are commonly known as "package
plants". However, it is important to note that discharges from package plants
represents about 33% of the total wastewater flow from FDEP package plants. The
remainder of the flow (67%) comes from discharges from a few large facilities with
permitted capacities exceeding 100,000 gpd (0.1 mgd).
All FDEP-permitted WWTP systems are required to meet, at a minimum,
secondary treatment and disinfection in accordance with Chapter 62-600 F.A.C.
That regulation requires supervision and monitoring of these facilities by a Florida
licensed operator and submission of discharge monitoring reports, containing all
required test results, for each month of operation. These facilities are also inspected
by FDEP personnel to ensure compliance with permit requirements.
Secondary treatment provides up to 90% removal of the total suspended
solids and organic (carbon) wastes producing oxygen demand (CBOD) in the
wastewater. This process also removes organic nitrogen and phosphorus associated
with the suspended solids, but does little to remove nutrients dissolved in the
wastewater, such as nitrates and phosphates. Chlorination is employed for
disinfection of the effluent in order to protect public and environmental health. The
wastewater sludge from the settled solids is periodically removed and transported to
the mainland for disposal at FDEP-permitted treatment facilities. Alternatively,
disinfected wastewater sludge can also be delivered to approved land application
sites for disposal, as long as the wastewater sludge meets the treatment criteria
specified in Chapter 62-640, F.A.C., and the Code of Federal Regulations Part 503.
Because of strict regulatory standards required for surface water discharges,
the primary method of effluent disposal employed by the package plants is
discharge to the groundwater by means of Class V wells. Currently there are 750
FDEP-permitted Class V wells in the Florida Keys. These disposal wells are
required to be drilled to a depth of 90 feet and lined with cement (cased) to 60 feet.
As of June 1997, Chapter 62-528, F.A.C. requires that all Class V wells designated
to inject domestic wastewater in Monroe County are required, as part of their
operation permit application, to provide reasonable assurance that operation of the
42
well will not cause or contribute to a violation of surface water standards as defined
in Chapter 62-302, F.A.C.
At least nine WWTP in Monroe County utilize wastewater reuse systems,
such as subsurface or spray irrigation, as either their primary or secondary effluent
disposal method. The use of drainfields and percolation ponds for groundwater
effluent disposal is also allowed in accordance with Chapter 62-610, F.A.C., but the
use of those systems is limited in Monroe County because they require large surface
areas and because of the lack of soil and high ground water table in the Keys.
CENTRAL SEWAGE SYSTEMS
Central sewage systems involve the collection of wastewater from multiple
sources by means of a sewer system and pumping the wastewater to a sewage
treatment facility for treatment and disposal. Construction of sewage collection
systems for wastewater is difficult and expensive in the Keys because of the rock
substrate. Central treatment of wastewater in a large volume sewage treatment
plant is very efficient because of the economy of scale and the presence of full-time
operators. There are two municipal central sewage collection and treatment systems
currently operating in the Keys: Key Colony Beach and Key West. In addition,
there are several privately owned utilities in Monroe County with central collection
systems, including Key West Resort Utilities (Stock Island), Key Haven Utilities,
Key West Naval Air Station, and Key Largo Utility (Ocean Reef Club). All these
facilities, with the exception of the City of Key West, use Class V wells and/or
wastewater reuse systems for effluent disposal.
The City of Key Colony Beach operates a wastewater treatment plant with a
current capacity of 0.22 mgd. This facility is over 28 years old and provides
secondary treatment of wastewater. Wastewater is collected through a gravity
sewer line system which includes 15 lift stations. The 20 to 30 year old collection
pipes are subject to infiltration of saline groundwaters, particularly during extreme
high tides. Prior to 1994, effluent was discharged directly to the Atlantic Ocean. In
late 1994, the discharge was rerouted to six Class V injection wells. The
wastewater treatment plant services 1,233 residential units and 96 business units.
The facility has not utilized reuse of treated wastewater for irrigation because the
cost of additional treatment facilities required and the need for increased operator
attendance are much greater than the cost of potable water presently being used to
irrigate greens of the nine-hole, par 3 golf course. Also, the high amounts of saline
groundwater infiltration into the collection system would make the effluent too
43
saline at times for irrigation use. Plans are being developed to replace the existing
facility with a facility that can achieve A WT standards. Efforts to correct the
infiltration problem are ongoing.
The City of Key West collects and treats wastewater at a central treatment
plant with a permitted capacity of 7.2 mgd of secondary treated wastewater.
Discharge is through a submerged ocean outfall located about 1000 meters (328 ft)
from the southern tip of Key West. The ocean outfall is the largest single source of
nutrient pollution in the Keys. In 1997, the effluent included an average of 342
pounds of nitrogen and 62 pounds of phosphorus daily. However, because of the
tremendous dilution at the location of the outfall, Ferry (undated) concluded
impacts from the ocean outfall are mainly limited to localized eutrophication and
some sewage contamination of the benthos in the immediate vicinity of the outfall.
The probability of transport of any significant amounts of pollutants or
contaminants from the outfall to offshore bank reefs appears to be low.
Key West is currently under an enforcement action by FDEP for violations
related to collection system failure and excessive infiltration. During 1996, a
Consent Judgement was prepared by FDEP requiring the City to take corrective
action to reduce the infiltration problem. The City has proposed a five-year
schedule and has initiated an aggressive sewer rehabilitation program. The level of
treatment currently approaches advanced treatment standards; since 1995, the
effluent has averaged 4.2 mgll nitrogen and 1.1 mgll phosphorus. Also, the City
has decided to eliminate the ocean outfall and inject treated wastewater into a deep
injection well drilled into the boulder zone (2500+ feet). The FDEP has issued and
intent to issue a deep well permit.
Key Haven Utility is a private system serving the subdivision of Key Haven
on Raccoon Key, located just east of Stock Island. The plant is currently permitted
for 0.20 mgd that is provided by two connected facilities. One unit was constructed
in approximately 1970 and is currently in poor condition. The second unit was built
in 1994. Plant upgrades are underway to replace the original unit. Improvements
should be completed in 1998. The wastewater collection system consists of a
gravity sewer with five lift stations. The collection system has a history of
infiltration problems. None of the treated wastewater is reused.
Key West Resort Utility provides service to approximately 90% of the Stock
Island area south of U.S. Highway 1. This includes approximately 600 residences
44
and several commercial establishments. Plant capacity is 0.499 mgd and the plant
is in excellent condition. The collection system consists of a gravity sewer, force
mains, and 13 lift stations. The primary disposal method is spray irrigation on the
Key West Golf and Country Club golf course located on Stock Island north of U.S.
1. The effluent is treated to public access reuse standards as required in Part III,
Chapter 62-610 F.A.C. Secondary disposal is to Class V injection wells during wet
periods of the year. The plant does not currently serve the entire area of the utility
district. Plans are currently underway for an expansion that will include the entire
utility area. Also, the utility is interested in expanding its boundaries to include
adjacent areas.
Key West Naval Air Station treatment plant has a capacity of 0.4 mgd and
serves the Naval Air Station. The plant has a history of exceeding peak flow
capacities and has significant infiltration problems. Improvements have been
recently made to
the plant and to the 11 lift stations. In addition, Class V wells have been installed to
better manage effluent disposal.
The Key Largo Utility serves Ocean Reef and Anglers Club developments
located at the extreme north end of Key Largo. The plant consists of two connected
units, one older than the other, and has a capacity of 0.55 mgd. Both units are in
good condition. The collection system consists of gravity sewers, force mains, and
37 lift stations. The collection system has infiltration problems that are currently be
improved by replacing older clay and cast iron pipes with PVC pipes. Effluent is
treated to secondary standards and disposed into Class V injection wells. The
facility does not currently provide for reuse because infiltration problems results in
an effluent with high chloride concentration. The three 18 hole golf courses in the
development currently irrigate using a 1.7 mgd reverse osmosis plant ($1.75 per
1,000 gallons). Complete rehabilitation of the collection system for reuse would be
more costly than costs of water from the reverse osmosis plant.
W ASTEW A TER FACILITIES PLAN FOR THE MARATHON AREA AND
PHASED IMPLEMENTATION FOR LITTLE VENICE (V ACA CUT TO 94TH
STREET)
In February 1996, Monroe County completed a Marathon Area Facilities
Plan. That plan originated in recognition of the need to develop a long-range
wastewater management plan for Monroe County. Marathon was chosen as the
fIrst area in Monroe County for this planning because of the large number of high
45
density developments with small lot sizes, a large number of identified cesspits, and
documented degraded water in canals. The purpose of the plan is to define the most
cost-effective, environmentally sound, and implementable program for the
management of existing and future wastewater pollutants that presently act, or will
act, to deteriorate the water quality in the Marathon area. The Plan will be a part of
a comprehensive Wastewater Master Plan for Monroe County. In general, three
steps comprise implementation of a wastewater management system: planning,
design, and construction. The Marathon Area Facilities Plan is the first step in the
implementation of a wastewater management system for the Marathon area.
The Facilities plan includes:
Evaluation of existing water quality;
Identification of existing point source pollution
sources;
Documentation of existing background environmental
conditions;
Preparation of an inventory of existing wastewater
plants;
Estimation of future waste loads and flows;
Development and evaluation of collection, treatment,
and disposal alternatives;
Identification of a potential site, or sites, for
location of treatment facilities;
Selection of the most cost-effective, environmentally
sound, and implementable wastewater management
alternative;
Development of conceptual design and planning level
cost estimates for the recommended plan;
Assessment of the recommended plan's environmental
impact; and
Discussion of the institutional framework and financial
requirements needed to implement the plan.
The Marathon Area Wastewater Facilities Plan concluded that a regional
wastewater collection, treatment, and disposal system be implemented to serve the
primary service area (Seven Mile Bridge to Coco Plum, excluding Key Colony
Beach). The recommended technology for the wastewater collection system is a
vacuum system, that would be comprised of vacuum collection mains, combination
46
vacuum/conventional pumping stations, and force mains. Based on direction
provided by the Monroe County Board of County Commissioners, the regional
wastewater treatment plant will treat the wastewater to A WT standards to provide a
high level of solids and nutrient removal. The recommended effluent management
system is deep underground injection of highly treated effluent to the Boulder Zone
(2,500 ft). The Plan recommends that reuse of effluent be explored. The estimated
capital and annual operation and maintenance costs for collection, treatment, and
disposal are given in Table 8.
In February 1996, the Monroe County Board of County Commissioners
approved the recommendations in the Facilities Plan provided that the connection
fee per household does not exceed $1,600 and monthly service fee does not exceed
$35. Monroe County has applied for a loan from the State Revolving Fund for
approximately $30 million for design and construction costs. In October 1997,
Congress, with the assistance of the Governor's Office and EP A Region 4,
appropriated $4.3 million of de-obligated Title II construction fund monies to be
used in wastewater improvements in Monroe County. These funds will be used by
amending the Marathon Area Wastewater Facilities Plan to include a first phase for
Little Venice (Vaca Cut to 94th Street on the ocean side of U.S. 1). An offer and
award of these monies is expected in October 1998 and design will begin in Fall
1999 after contracts have been approved. Construction should begin in 2001 and be
completed by early 2002.
During the second session of the 105th Congress, Monroe County and others
spent considerable time working with Congress to develop additional wastewater
funding proposals for the Marathon Area Facilities Plan and for the projected needs
for the remainder of Monroe County. Included in these discussions was the
concept of developing a non-transportation toll on U.S. 1, located somewhere north
of Key Largo. Efforts are on-going and will continue in the 106th Congress and
beyond.
MONROE COUNTY W ASTEW A TER MASTER PLAN
Monroe County initiated the development of a county-wide Wastewater
Master Plan in August 1997. The purpose of the Wastewater Master Plan is to
identify environmentally acceptable and cost effective wastewater treatment and
disposal alternatives for geographic service areas within the Florida Keys.
Different wastewater management practices, from onsite systems to community
47
and/or regional collection and treatment systems, will be evaluated for each
geographic service area and the costs and environmental benefits compared. The
cost of development of the Wastewater Master Plan is approximately $2.2 million.
The plan will be completed in December 1999.
At the outset, Monroe County and the Water Quality Protection Program
Steering Committee approved a Technical Advisory Committee (T AC) consisting
of approximately 20 individuals with interest and/or special knowledge and
expertise to oversee the development of technical documents produced in the
project. The T AC will review work products and meet with the consultant
approximately six times during the course of the project. When complete, the
Wastewater Master Plan will be evaluated by the Water Quality Program Steering
Committee and approved by the Board of County Commissioners (BOCC).
New legislation has been recently passed regarding the authority of the
Florida Keys Aqueduct Authority to function as a wastewater utility. A
Memorandum of Understanding has been finalized between Monroe County and the
FKAA regarding the agencies' roles in wastewater. Based upon that Memorandum,
it is anticipated that the FKAA will begin to assume a greater role in the further
development and review of the Wastewater Master Plan. After the BOCC approves
the Wastewater Master Plan, it will be provided to the FKAA for implementation.
It is expected that FKAA will become the utility authority for only the most densely
populated areas of the Keys.
CESSPIT IDENTIFICATION AND REPLACEMENT
In conformance with the Governor's Executive Order 96-108 and Polity
901.2 of the Monroe County Year 2010 Comprehensive Plan, Monroe County and
the FDOH initiated a five-year operating permit procedure for onsite disposal
systems. The ordinance requires homeowners to have their onsite disposal system
inspected within 30 days of notification. Notification dates are based upon the age
of the structure; older structures are notified fIrSt. Inspection results must be
submitted to the FDOH. Disposal systems found to be in compliance with current
requirements will receive a five-year operating permit. Disposal systems that are
found to be in compliance with requirements in place when the structure was built,
48
but do not meet current minimum standards, will receive a two-year temporary
operating permit. Those systems must be replaced within two years. Structures
found to have cesspools or a septic tank that does not meet the standards in place at
time of construction must comply with current standards within 180 days of written
notice.
Low interest loans are available to assist homeowners in funding replacement
of inadequate on site disposal systems. Homeowners in the Marathon Service Area
have been exempted from compliance with this ordinance because central collection
and treatment was determined to be the most cost effective and environmentally
acceptable solution of wastewater disposal in that service area. In other geographic
areas, homeowners with an approved system for which an operating permit has
been obtained may continue to use the approved system so long as:
1. The system is properly maintained and remains in
satisfactory operating condition;
2. The operating permit is properly renewed;
3. An approved sewage treatment plant has not been
available for connection for longer than 365 days; and
4. No alterations are made to the residence, commercial
structure, or site that would change the sewage or
wastewater characteristics, increase sewage flow, or
impede the performance of the onsite disposal system.
CANAL BEST MANAGEMENT PRACTICES
There are many simple activities that homeowners can undertake that will
help improve water quality in canals adjacent to residences. Activities can be
divided into two categories:
1. Reduce nutrient loading into canal water; and
2. Increase circulation and flushing (where
applicable ).
1. Reduce Nutrient Loading
Because canals generally exhibit poor circulation and flushing, they are very
susceptible to eutrophication due to excess nutrients. The following activities are
required to minimize nutrient loading into canals:
. Eliminate cesspits
49
Install adequate drainfields for septic systems that results in binding of
nutrients.
Pump out septic tanks on a regular basis to prevent organic loading
from tanks full of sludge.
Do not apply fertilizers on lawns or other vegetation adjacent to
canals.
Do not dispose of organic wastes into canals, including grass
clippings, animal droppings, fish carcasses, etc.
Slope lots adjacent to canals so that surface drainage is directed away
from canals.
Eliminate fast growing exotic vegetation from canal banks (e.g.,
Australian pine, Brazilian pepper) and maintain native vegetation (e.g.,
buttonwood and mangroves) as a buffer.
Use phosphate-free detergents.
Do not discharge gray water onto soil or into canals.
No live-aboard discharges into canals.
2. Canal Circulation
Deep, dead end canal systems exhibit poor water quality due to the geometry
of the canal system. Several physical alterations can be attempted that may improve
canal water quality. These include:
Backfilling canals to a maximum of -6 ft MSL at the mouth of the
canal and sloped to -4 ft MSL at its distal end.
Aerating canal waters to assist vertical circulation.
Dredging canals or otherwise treating canal bottoms to remove
accumulation of organic, oxygen-demanding sediments.
Install flushing channels/culverts in suitable areas if actions will not
degrade receiving waters.
The orientation of some canals make them susceptible to accumulation of
wind-driven, floating organic matter, predominantly seagrass leaves. Physically
preventing transport of floating organic matter into canals will improve quality of
canal waters. Floating booms, air curtains, and other devises are used as weed gates
at mouths of canals.
There are several canal systems in the Keys that were constructed but never
connected to adjacent waters. Those canal systems are plugged with fill material at
their mouths. Recently, there has been increased interest in removing the plugs
50
from those canal systems to connect them with adjacent surface waters. Removal of
plugs requires federal, State, and County permits. Permit agencies recognize that
existing open canal systems represent a source of degraded water quality to
receiving waters and that water quality within open canals may violate State water
quality standards. Therefore, there is a great reluctance to consider requests to open
additional canal systems. Before such a request can be considered, there must be
overwhelming evidence that the canal currently does not violate water quality
standards and that opening of the canal system will not degrade receiving waters.
Generally, currently plugged canals systems will not meet those requirements.
DISCHARGES FROM VESSELS
There is a large community in the Keys that live on boats. Many live-aboard
vessels are permanently anchored in harbors and are not capable of movement.
Transient vessels also anchor in harbors and other protected sites and are very
numerous in winter months. The number of live-aboard vessels has increased
dramatically in recent years. For example, the number of live-aboards in the Key
West area increased from 235 in 1992 to 393 in 1995 (Monroe County Grand Jury
Report). Approximately 400 anchored or moored vessels were observed in Boot
Key Harbor (Marathon) in February 1995 (Kruczynski, personal communication).
A Monroe County Grand Jury received testimony that up to 80% of live-aboard
vessels do not use sewage dumping facilities.
The Clean Vessel Act (Florida Statute 327.53) prohibits the discharge of raw
sewage from any vessel, houseboat, or floating structure into Florida waters. A
houseboat is a vessel that is used primarily as a residence (21 days out of any 30
day period), and its use as a residence precludes its use as a means of transportation.
Houseboats and floating structures must have permanently installed toilets attached
to Type III Marine Sanitation Devises (MSD) or connect their toilets directly to
shore-side plumbing. A Type III MSD is one that stores sewage onboard in a
holding tank for pumpout. Houseboats may also have other approved MSDs on
board; but, if they do, the valve or other mechanism selecting between devices shall
be selected and locked to direct all sewage to the Type III device while in State
waters. All vessels that have MSDs capable of flushing raw sewage directly
overboard or of being pumped into a holding tank, shall set and secure the valve
directing all waste to the holding tank, so that it cannot be operated to pump
overboard while in State waters. All waste from a Type III MSD or from portable
toilets shall be disposed in an approved sewage pumpout or waste reception facility.
51
While the Clean Vessel Act prohibits the dumping of raw sewage, treated
wastewater from transient vessels may be discharged into State waters. Wastewater
treatment (disinfection) by Type I and II MSDs does not remove nutrients from
wastewater. Graywater does not have to be stored or treated from any vessel and
may be discharged directly into water of the State.
There are few land-based pumpout facilities in the Keys and no mobile
pumpout facilities. There is one land-based pumpout facility in Boot Key Harbor.
Thus, many live-aboard vessels and most transient vessels discharge wastewater
into surface waters. It is estimated that nutrients from vessel wastewater account
for 2.8% of nitrogen and 3.0% of phosphorus loadings into nearshore waters of the
Keys (Table 4). Although nutrient loadings from vessels may be relatively minor
contributions to the total loading, loadings from vessels are a significant source to
harbors and result in eutrophication of waters that typically exhibit poor
circulation/flushing. Violations of fecal coliform standards are common in marinas
and harbors (FDER 1987, 1990).
The EP A, State, Monroe County, and the City of Key West are pursuing the
designation of marinas, harbors and anchorages as "no discharge zones" (NDZ).
The NDZ designation will require all boats, live-aboards and transients, to use Type
III holding tanks and have wastes pumped at approved facilities. Federal
regulations require that adequate pumpout facilities be available before an area is
designated as a NDZ. Plans are being developed for construction of land-based and
mobile pump out facilities and for strict enforcement of the prohibition against
disposal of wastewater into surface waters of the State.
STORMWATERTREATMENT
Stormwater runoff can be successfully treated with the use of one or more
"Best Management Practices" (BMPs). Stormwater treatment BMPs in Florida
typically are described in Florida Department of Environmental Regulation
(undated) and usually consist of a retention or detention facility, such as a pond or
large swale area. These facilities are designed to capture 80 to 95% of the runoff.
Effectiveness of BMPs can vary, however. One national study of pond BMPs used
in urban areas found that about half of the phosphorus was removed from the runoff
and roughly one-third of the nitrogen (Center for Watershed Protection, 1997).
Therefore, even under the best of circumstances, treatment of the runoff
downstream raises several questions:
52
1. What are the water quality criteria or success
criteria to be met?
2. What are the sources of pollutants?
3. How much land is available to install BMPs?
4. What types of BMPs will be most effective?
Waters surrounding the Florida Keys are Outstanding Florida Waters (OFW),
one of the most protective in State law. Where a discharge to an OFW is permitted,
the SFWMD requires that ambient water quality is not degraded. Specific water
quality targets for some substances are listed in Appendix K of the OFW report to
the Environmental Regulation Commission (FDER, 1985). Currently, all
stormwater systems permitted in the Keys by the SFWMD must retain from 1 to 2.5
inches of runoff on site. Most storm events are less than this, so discharge volumes
are zero most of the time. Where an outfall discharges into the OFW, an additional
1 to 1.25 inches (50%) must be retained on site. These design criteria are presumed
to achieve OFW water quality criteria, although a detailed analysis for the Keys has
not been conducted.
Source control is an important issue. If pollutants can be prevented from
entering the runoff stream at the source, it can greatly reduce the expense of treating
runoff downstream. This can often be accomplished by implementing better
housekeeping practices on individual properties and can sometimes save property
owners money. A homeowner, for example, may use less fertilizer and get identical
results. A business owner may find that captured wastes can be recycled and turned
into an asset. Government and educational programs like "Florida Yards and
Neighbors" can assist property owners in identifying low cost ways to reduce
pollutant loads.
The very limited land available in the Florida Keys profoundly affects the
types of BMPs that can be utilized. The typical land-intensive BMPs used
elsewhere in Florida are not feasible in the Keys. There are, however, BMPs
utilized in urban areas of south Florida that can be implemented in the Keys. These
BMPs take advantage of salt intruded groundwater and high percolation rates of the
soils. In some cases, pumps may be required because of low elevations. No single
BMP is typically adequate to treat a runoff stream. Well designed stormwater
treatment systems include a series of BMPs that ensures that as much as possible of
the pollutant load is removed.
53
These issues and the issue of where and how to best spend public funds to
improve stormwater runoff in the Keys is best analyzed within the context of a
master plan. A good
stormwater master plan will include an objective evaluation and recommendations
tied to specific outcomes. Some of these kinds of analyses have been conducted in
specific locations, like Key Colony Beach. However, a regional plan is needed. To
this end, Monroe County and the SFWMD have established a partnership. Monroe
County is developing the scope of work for a master plan. Once the project is
"scoped", professional services can be retained to complete the plan. One of the
areas of investigation in the plan will be the issue of "hot spots" of water quality
degradation. Hot spot areas will be evaluated to determine what portion of the
pollutant load could be related to stormwater runoff. The plan will recommend
measures that will be effective for remediation in those areas. The plan will include
a state-of-the-art load analysis for the Keys. It will examine current design
feasibility of various BMPs.
Implementing stormwater treatment measures in the Keys will be very
expensive. The cost of stormwater improvements is estimated to be between $370
million and $680 million, depending on the percentage reduction in stormwater
pollutant loadings to be achieved and areas selected for retrofitted treatment BMPs
(EPA,1993).
CARRYING CAPACITY
Ecosystems are able to assimilate and adjust to certain levels of stresses.
When stresses reach threshold levels, a change to the ecosystem structure and
function will occur. Some changes are acceptable or reversible once the stress is
removed. Other changes are detrimental and permanent and can lead to the collapse
of the existing ecosystem. Carrying capacity is an ecological concept that
delineates acceptable limits of stresses to an ecosystem.
Carrying capacity analysis can defme threshold limits of nutrients that will
result in eutrophication of waters. As a result of a legal challenge of the Monroe
County Comprehensive Plan, the State Hearing Officer in that case determined that
the nearshore waters adjacent to the Florida Keys have exceeded the carrying
capacity for assimilation of nutrients.
54
Determining the number of people a geographic area can support without
irreversible or unacceptable damage to the ecosystem is a complex analysis.
Carrying capacity has many components including socio-economic, aesthetic,
public health and safety, as well as environmental. Quantifying these elements
requires defensible data and consensus on assumptions of thresholds, limiting
factors, and acceptable limits.
The U.S. Army Corps of Engineers has completed a "Draft Scope of Work"
for a carrying capacity analysis of the Florida Keys. The Scope has been submitted
to the Florida Department of Community Affairs and it is being reviewed by
experts in carrying capacity analysis. The results of this important study will be
used by planners in setting acceptable limits of growth and use of this important and
unique ecosystem.
MONITORING
A long term, comprehensive monitoring program is required by the Florida
Keys National Marine Sanctuary and Protection Act. Monitoring is critical in
maintaining and improving the ecological condition of the Sanctuary since it will
provide information on the status and trends of water quality and important
biological parameters. Data generated by monitoring programs will provide
managers information necessary to identify or confrrm problem areas. In addition,
monitoring is required to evaluate the effectiveness of corrective actions taken to
reduce pollution sources. Water quality, coral reef and hard bottom, and seagrass
monitoring programs were designed in 1993 (U.S. EPA, 1993) and finalized in
1995 (U.S. EPA, 1995).
WATER QUALITY
The Water Quality Monitoring Program uses a stratified random design
based upon the EP A Environmental Monitoring and Assessment Program (EMAP)
hexagonal grid (Overton et al., 1990). Strata were based upon variability of
physical transport regimes, as described by Klein and Orlando (1994). Nearshore
to offshore transects are randomIy located within strata (Figure 1). Segment 1
includes the Tortugas and surrounding waters and is most influenced by the
Tortugas gyre of the Loop Current (Lee et al., 1994). Segment 2 includes the
Marquesas Keys and the Quicksands. Segment 4 is the shallow waters around the
myriad of keys in the "Back Country". Segment 6 is the Sluiceway that is heavily
55
influenced by transport from Florida Bay and Gulf shelf waters. Segments 5, 7, and
9 include inshore, Hawk Channel, and reef tract waters on the Atlantic side of the
Keys.
Approximately 150 stations have been sampled quarterly since March 1995.
Data for 1997 are summarized in Figures 2 to 5. Several trends are apparent in the
data. Silicate is an indicator of freshwater and was highest in the Sluiceway (6) and
Back Country (Figure 2). Total phosphorus was highest in Back Country and
Sluiceway and lowest in the and Upper Keys (9). Total inorganic nitrogen was
highest in the Back Country and at stations adjacent to the Keys in the Upper(5) and
Middle (7) Keys. Chlorophyll was highest in the Marquesas Quicksands (2),
probably due to Gulf shelf water input, and lowest in the Tortugas and Upper Keys.
Turbidity was highest and most variable in the shallow waters of the Back Country
and Sluiceway and lowest in the Tortugas.
Concentrations of total inorganic nitrogen, total phosphorus, silicate, and
turbidity were highest inshore and declined toward the reef tract (Figures 3 and 4).
Lower and Middle Keys had much higher nearshore concentrations than Upper
Keys. Total inorganic nitrogen, total phosphorus, silicate, chlorophyll, and
turbidity were highest in individual transects situated along passes between the
Keys, indicating the prevalence of Sluiceway and shelf influence (Figure 5).
Waters in Biscayne Bay passes had lower concentrations of nutrients compared to
waters in passes between the Keys.
CORAL REEF AND HARD BOTTOM
There is very little existing robust information on long-term changes in coral
reef ecosystems. The Coral Reef and Hard Bottom Monitoring Program is designed
to evaluate the status and trends of 40 permanently located reef and hard bottom
sites. Stations have been observed annually using video techniques since 1996. A
summary of the data on number of taxa by habitat type for 1996 and 1997 are
shown in Figure 6. Although it is much too early to detect long term trends and
variability, mean species numbers declined for patch reef and offshore deep reef
stations. In addition, coral diseases appear to have significantly increased, whether
reported in terms of number of monitoring stations affected, number of coral
species affected, or number of different diseases recorded.
56
SEAGRASSES
A comprehensive seagrass monitoring program in the Sanctuary has been in
place since 1996. Distribution, productivity, and morphometrics of seagrasses are
monitored quarterly throughout the Sanctuary. Sampling is performed at three
levels. At Level I sites, shoot morphometrics and productivity of turtlegrass are
measured quarterly. Level II sites are sampled annually to obtain shoot
morphometrics. Level III sites are sampled annually to assess percent cover.
Locations of sites sampled in 1996 and 1997 are shown in Figure 7. There are
approximately 30 Level I stations, 87 Level II stations, and 187 Level III stations.
Level I sites were selected to conform with water quality monitoring sites. Level II
and III sites are randomIy located within segments using the EMAP grid system.
The mix of site types is designed to monitor trends through intense quarterly
sampling of a few permanent locations (Level I) and to annually
characterize the broader seagrass population through less intensive, one-time
sampling at more locations (Level II and III).
Turtlegrass and manatee grass are the most stable and widely distributed of
the seagrasses within the Sanctuary(Figures 8). The overall average standing crop
biomass 21.9 g/m2 for turtlegrass and 8.2 g/m2 for manatee grass (above ground,
dry weight). Seasonal variations of standing crop and productivity are evident,
with increases in third and fourth quarters of sampling (Figure 9). Short shoot
density of turtlegrass ranged from 66 to 1025/m2 for all sites. Above sediment
standing crop ranged between 5 and 93 g/m2. Leaf mass exhibited high variation
(21 to 415 mg/short shoot). Short shoot production ranged between 0.18 and 8.31
mg/short shoot/day. Higher values were observed in Florida Bay than on the
Atlantic side. Areal productivity ranged between 0.07 and 3.37 g/m2.
The seagrass monitoring has not observed the marked effects of nutrient
enrichment described by Lapointe et al. (1994). The reason, at least in part, is
probably due to differences in sampling methodologies employed. Lapointe et al.
(1994) selected hypereutrophic areas associated with a known source of pollutants
and sampled transects from those sources. They found gradients in nutrients and
biological changes along the transects that they attributed to source pollutants. The
long term seagrass monitoring program is on a much broader scale and utilizes a
random sampling pattern. If the observations of Lapointe et al. (1994) are more
widespread than their selected sampling sites, the seagrass monitoring program
should detect similar variations when enough samples are taken. To date this has
not been the case.
57
THE ECONOMICS OF CLEAN WATER AND NATURAL RESOURCES
Natural resources have market values and non-market values. Market values
are the prices of commodities on the open market (e.g., an acre of land). Non-
market values are less immediately tangible and include the values of being part of
a balanced, self-sustaining ecosystem (e.g., habitat value). Effects of habitat loss
and other non-market values may take years to become apparent, but these values
have long lasting socio-economic effects. A sustainable market economy depends
on maintenance of non-market values over long time periods. For example, the
tourist-based economy of the Florida Keys depends upon clean water and abundant
natural resources. If non-market values of these resources decline, the market value
will eventually decline.
Leeworthy and Bowker (1997) recently quantified the non-market value of
natural resources in the Florida Keys. The study estimated that values tourists
receive from the natural resources that are over and above the costs for them to
come to the Keys to use them. The study determined that the overall non-market
user value for visitors to the Florida Keys is $654 per visitor per trip, or $1.2 billion
annually. The study estimated that 76% of all activity days by visitors are spent in
some sort of natural resource-related activity. Thus, the amount of non-market
value attributed to natural resources is $910 million annually (76% of $1.2 billion).
When market values ($1.3 billion) are added to non-market user values ($1.2
billion), the total annual value of the Florida Keys to tourism is $2.5 billion.
In a sustainable economy, market values do not come at the expense of
declines in non-market values. Non-market user values calculated on a sustainable
basis are called asset values, which are a long-term market value. The total non-
market value of the Florida Keys to tourism was calculated to be $24.1 billion and
the natural resource total market value was calculated to be $18.3 billion.
Non-market user values can be used in benefit-cost analysis of projects that
impact natural resources. For example, the cost to improve wastewater and
stormwater treatment in the Keys to improve water quality of surface waters may
range from $500 million to $1 billion million depending on options selected (U.S.
EP A, 1996). Although that is a large cost, it is small compared to the estimated
$2.5 billion in annual market and non-market values of tourism to the Keys. Even
if just the annual natural resource non-market value of $910 million per year is used
58
as a comparison, the investment to improve water quality still makes sound
econormc sense.
Cost of water quality improvements (assume $1 billion) are only 5.5% of the
long term asset value of the natural resource ($18.3 billion). Clearly, the costs of
water quality protection and improvement measures are a relatively small
proportion of the non-market economic user value of the resources they are
designed to protect.
59
Table 1. Parameters measured in routine water quality monitoring and examples
of methods of analysis.
Water Quality Parameter
Examples of Methods of Analysis
Physico-chemical parameters
Temperaure
thermistor or mercury thermometer
Conductivity/salinity
elecrometric
Dissolved oxygen
pH
Winkler titration or polarographic sensor
electro metric
Light attenuation
PAR attenuation
Turbidity
Secchi disk or nephelometryibeam attenuation
Depth
measured line or presssure transducer
Nutrients
Dissolved ammonia
indophenol
Dissolved nitrate and nitrite
diazo after Cd reduction
Dissolved nitrite
diazo
Total nitrogen
high temperature combustion
nitrous oxide chemoluminenscence
Soluble reactive phosphorus
molybdate
Total phosphorus
high temperature digestion
molybdate
Non-purgeable organic carbon
high temperature
combustionlIR detection
Biological parameters
Chlorophyll a
fluorometric
Alkaline phosphatase activity
fluorometric
Fecal coliform bacteria
incubation and plate count
Biochemical oxygen demand
incubation and oxygen analysis
61
Table 2. Ranges of water quality parameters measured during a survey
to support designation of waters surrounding the Florida Keys as Outstanding
Florida Waters (From: FDER, 1985).
Water Quality Parameter Ambient Stations Canals
(mgll, except pH) (mgll, except pH)
Dissolved oxygen 6.0-9.4 0.0-9.6
pH 7.0-8.4 7.3-8.3
Total phosphorus 0.001-0.054 0.005-0.083
Total Kjeldahl nitrogen 0.128-0.693 0.196-1.15
Ammonia nitrogen 0.051-0.160 0.057 -0.239
Organic nitrogen 0.019-0.580 0.066-0.850
Nitrate plus nitrite 0.000-0.027 0.002-0.054
62
Table 3. Nutrient loadings from residential wastewater. Typical residential wastewater
flow is 45 gallons/capita/day (from: Harkins, 1996).
Total Nutrient Loading (gmlpersonlday) by Fixture
NUTRIENT TOll..ETS SINKS, TOTAL WITHOUT TOTAL WITH
SHOWERS GARBAGE GARBAGE
DISPOSL DISPOSAL
carbon 18 30 48 59
nitrogen 6.5 1.5 8.0 9.0
phosphorus 1.2 2.8 4 4.0
Nutrient Concentration of Wastewater (mgll)
NUTRIENT WITHOUT GARBAGE WITH GARBAGE
DISPOSAL DISPOSAL
carbon 280 350
nitrogen 47 53
phosphorus 24 24
63
Table 4. Estimated Nutrient Loading (pounds per day) in the Florida Keys by Source
(from: U.S. EPA, 1993, Table 3-1, as revised by Robert Freeman, Fred McManus, and Bill
Thiess ).
SOURCE NITROGEN PHOSPHORUS
pounds/day percent pounds/day percent
Wastewater
OSDS 932 30.9 226 23.0
cesspits 283 9.4 100 10.2
package plants 758 25.2 152 15.5
central 320 10.6 36 3.7
treatment plants
Ii ve-aboards 84 2.8 30 3.0
2377 78.9 544 55.4
SUBTOTAL
Stonnwater
developed 401 13.3 364 37.0
areas
undeveloped 234 7.8 75 7.6
areas
635 21.1 439 44.6
SUBTOTAL
TOTAL 3012 100 983 100
64
Table 5. Florida Keys Water Quality "Hot spots": Areas with Known or
Suspected severely degraded Water Quality (From: U.S. EPA, 1993 Table
6-4, as revised on March 19, 1996 by an Interagency Panel. '
10 #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44,'
~
Ocean Reef Marina
Phase I and Dispatch Creek
Werla3 BeyeRd DELETED.PURCHASED BY STATE
C-111 Canal
Sexton Cove and lake Surprise Subdivisions
Cross Key Waterways Subdivision
Port Largo
Key Largo Fishery Marina
Marian Park and Rock Harbor Estates
Pirate Cove Subdivision
Winken, Blynken, and Nod
Blue Water Trailer Park
Hammer Point
Campbell's Marina
Tropical Atlantic Shores Subdivision
Plantation Key Colony.
Indian Waterways
Plantation Yacht Harbor
Treasure Harbor
Venetian Shores
Holiday Isle Resort
Islamorada Fish House
Lorelei Restaurant
Stratton's Subdivision
Port Antigua
White Marlin Beach
Lower Matecumbe Beach
Caloosa Cove Marinaa
Kampgrounds of America Marina
Long Key Estates and City of Laytona
Outdoor Resorts of America
Conch Key
Coco Plum Beach areaa
Bonefish Towers Marinaa
Key CeleRY Seae'" Sewa~e Outfall INJECTION WELL
Coco Plum Causeway NEW
Key Colony Subdivisiona
Sea-Air Estates
90111 Street Canal
Winner Docks
National Fish Market
Faro Blanco Marina
Boot Key Marina
Boot Key Harbor drainage area
Marathon Seafood
Little Venice
NEW
NEW
NEW
NEW
65
Location
Key Largo
Key Largo
Key Lafgo
Mainland
Key Largo
Key Largo
Key largo
Key Largo
Key Largo
Key Largo
Key Largo
Key Largo
Key Largo
Key Largo
Plantation Key
Plantation Key
Plantation Key
Plantation Key
Plantation Key
Plantation Key
Windley Key
Upper Matecumbe Key
Upper Matecumbe Key
Upper Matecumbe Key
lower Matecumbe Key
Lower Matecumbe Key
Lower Matecumbe Key
Lower Matecumbe Key
Fiesta Key
long Key
Long Key
Conch Key
Fat Deer Key
Fat Deer Key
Fat Deer Key
Fat Deer Key
Vaca Key (Marathon)
Vaca Key
Vaca Key
Vaca Key
Vaca Key
Vaca Key
Vaca Key
Vaca Key
Vaca Key
Vaca Key
llU
45
46
47
48
49
50
51
52
53
54
55
56
57-
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
Table 5. continued
~
Location
Knight Key Campground
Sunshine Key Marina
Bahia Shores
Doctors Arm
Tropical Bay
Whispering Pines Subdivision
Sands Subdivision area
Eden Pines Colony
Pine Channel Estates
Cahill Pines and Palms
Port Pine Heights
Sea Camp.
Coral Shores Estates
Jolly Roger Estates
Breeze$wept Beach Estatesa
Summerland Key Fisheries
Summerland Key Cove
Cudjoe Ocean Shore
Venture Out Trailer Park
Cutthroat Harbor Estatesa
Cudjoe Gardens Subdivisiona
Orchid Park Subdivision
Sugar Loaf Shore Subdivision
Sugar Loaf Lodge Marinaa
"Bay Point Subdivision
Porpoise Poin~
Seaside Resort
Gulfrest Park.
Boca Chica Ocean Shores
Tamarac Park
Boca Chica Naval Air Station
Key He'IeR St:Jbdi'lisiefl DELETED
Boyd's Trailer Park
Alex's Junkyard
Ming Seafood
Oceanside Marina
Safe Harbor
Key West Landfill
House Boat Row
Garrison Bight Marina
Navy/Coast Guard Marina and
Trumbo Point Fuel Storage Facility
Truman Annex Marina
Key West Sewage Treatment Plant Outfall
Key West Bight NEW
Key West Stormwater Discharge NEW
Knight Key
Ohio Key
No Name Key
Big Pine Key
Big Pine Key
Big Pine Key
Big Pine Key
Big Pine Key
Big Pine Key
Big Pine Key
Big Pine Key
Big Pine Key
Little Torch Key
Little Torch Key
Ramrod Key
Summerland Key
Summerland Key
Cudjoe Key
Cudjoe Key
Cudjoe Key
Cudjoe Key
Lower Sugarloaf Key
Lower Sugarloaf Key
Lower Sugarloaf Key
Saddlebunch Keys
Big Coppitt Key
Big Coppitt Key
Big Coppitt Key
Geiger Key
Geiger Key
Boca Chica Key
Raee66R Key
Stock Island
Stock Island
Cow Key
Cow Key
Cow Key
Key West
Key West
Key West
Key West
Key West
Key West
Key West
Key West
· Potential water quality degradation. No data available.
66
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Table 6. Water quality data from selected Bay Watch monitoring sites (Bay Watch, 1997).
Total N (uM) Total P (uM) Chlorophyll-a (ugll)
Grassy Key (open) 19.8 0.34 0.57
Duck Key Canal 19.8 0.21 0.28
Eden Pines Canal 40.5 1.04 2.78
Ramrod Key Canal 35.8 0.64 2.27
70
Table 7. Percent Nutrient Removal by Central Treatment and Onsite Treatment Systems
(from Harkins, 1996).
Pollutant Central Treatment Systems Onsite Treatment Systems
Secondary Adv. Sec. AWT Septic Aerobic Compo sting
Toilet
Carbon 85 97 97 44 77 65
Nitrogen 12 13 93 4 17 82
Phosphorus- 10 13 93 15 9 40
no ban
Phosphorus- 20 26 86 30 18 81
with ban
Pollutants Remaining after Treatment (grams/person/day)
Pollutant Central Treatment Systems Onsite Treatment Systems
Secondary Adv. Sec. AWT Septic Aerobic Composting
Toilet
Carbon 7.2 1.4 1.4 26.9 11.0 16.8
Nitrogen 7.0 7.0 0.6 7.7 6.6 1.4
Phosphorus- 3.6 3.5 0.3 3.4 3.6 2.4
no ban
Phosphorus- 1.6 1.5 0.3 1.4 1.6 0.4
with ban
71
Table 8. Estimated Costs for Marathon Central Collection and Treatment.
All costs are 1995 dollars (from Draft Wastewater Facilities Plan
for the Marathon Area of the Florida Keys, February 1996).
ITEM
AMOUNT (MILLIONS)
A. Construction Costs
1. Collection!I'ransmission System
2. Wastewater Treatment Plant
3. Effluent Disposal System
4. Solids Management System
5. Land Acquisition
$29.1
$ 5.0
$ 2.3
$ 1.7
$ 3.5
Subtotal $41.6
B. Other Project Costs
1. Contingency (25%) $10A
2. Engineering, Legal, Administrative (15%) $ 6.2
3. Financing (assume 33.3% financed @ 12%) $ 2.3
Subtotal $18.9
TOTAL CAPITAL COSTS $60.5
C. Annual Operation and Maintenance $ 1.4
D. Annual Renewal and Replacement $ 0.1
E. Administrative Costs $ 0.4
72
Figure 1. Location of segments (strata) in the Florida Keys National Marine Sanctuary
and location of water quality monitoring stations.
. J
~
.
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..
,. N,,,UUI un.,.
~
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FLORIDA
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i
INSET FIGURE
(SEGMENT 4)
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ATLANTIC
OCEAN
SEE INSET FIGURE
(SEGMENT 4)
~
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73
Figure 2. Water Quality Values for 1997 by Strata. Center horizontal line in the box
is the median, the top and bottom of the box arethe 25th and 75th quartiles, and the ends of the
whiskers are the Sib and 951b percentiles. The notch is the 95% confidence interval of the
median. When notches between boxes do not overlap, the medians are significantly different.
74
Figure 3. Water Quality Values for 1997 for Onshore-Offshore Transects in Upper (9),
Middle (7), and Lower (5) Keys and other sites. See legend for Figure 2. When notches
between boxes do not overlap. the medians are significantly different
1.5
1.0
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0.7
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Total Inorganic Nitrogen
'* j.*., "~**
,,""
1*
Chlorophyll a
Turbidity
lD CD CD lD CD CD ! ! CD ~ CI) >0- r;
'2 III (,)
.... ... lD C ~
0 C lD 0 C lD ~ iii
r; c a: r; c a: c a: ::I III c>>
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75
Figure 4. Water Quality Values for 1997 for Onshore-Qffshore Transects
in Upper (9), Middle (7), and Lower (5) Keys and other sites.
See legend for Figure 2. When notches do not overlap, medians are
significantly different.
38
Salinity
37 '~*'T
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Q.
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