Ecosystems of Florida
In an article by Brenner, Binford and Deevey, 1990, gives an estimate of the number of
lakes in Florida at 7,800. Their measurement for a lake is that it must be of a minimum size of
0.4 hectares of surface water. Below this size a body of freshwater is a pond. There is no
estimate for the number of ponds in Florida. A look at the aerial image below will give some
idea of the extent of lakes in Florida.
NASA satellite image of Florida lakes and estuaries
The separation in size from a pond to a lake is somewhat of an arbitrary division. Other size
differences can be used, however, the ecology of lakes and ponds can be considered as one.
Formation of lakes
There are several mechanisms involved in the formation of lakes in Florida.
Solution: these are lakes formed by depressions in the landscape. When the land sank
thousands of years ago, depressions were formed that ultimately became lake. Some of
the larger lakes grew in size following the post-glacial sea level rise.
Uplift: Lake Okeechobee is the second largest lake in the United States (1,840 km2). The
lake may have been formed as an irregular marine surface at the bottom of the sea in the
Pliocene that later became a lake as the land uplifted around it.
Deflation: this is the formation of lakes as land collapses into a sinkhole. The sinkhole
spreads, fills with water from rain or runoff, and becomes a lake. The aquifer may also
add water to the lake. Since the limestone aquifer is so extensive in Florida, sinkholes
occur often enough to create ponds regularly.
Erosion: The erosion of banks along streams and river can sometimes become so great
that ponds and lakes are “split” off from the water flow.
Lakes in Florida have the typical chemistry of most lakes, however, there are a few
features that make Florida lakes unique. Phosphoric sands and clays come from the Miocene
Bone Valley and Hawthorne formations in Central Florida. These deposits add phosphorus to the
water. Physical parameters of these lakes are: conductivity 115, pH 6.5, total phosphorus 82,
chlorophyll 12 and color 58. (Data from Hendry and Brezonik , 1984).
Other lakes in Florida that extend two-thirds of the length from Lake Okeechobee to
Georgia have different characteristics. Phosphatic sands do not influence them. Chemistry for
these lakes is: conductivity 33 - 45, pH 5.7, total phosphorus 12, chlorophyll 2.1 and color 3 –
Many (less than half) lakes in Florida have calcium carbonate dissolved in the water as a
result of the close proximity to the aquifer. In these lakes the high alkalinity results in a buffered
system. Lakes without this buffering system may suffer from acidification, the results of which
may be fewer plants, and less phytoplankton. In addition, most lakes have some level of tannic
acid as a result of decomposition of leaves. This coloration makes some lakes and streams appear
The “health” status of a lake is a public concern. In ecology the status of a lake may be
measured by the nutrients that are found in the lake, the amount of chlorophyll, the light
penetration (turbidity) or the amount of nutrients that are found in the lake (nitrates, nitrites,
phosphates, etc). A lake’s status may be classified as:
Oligotrophic: low in nutrients, low in productivity, and low in number of organisms.
Eutrophic: high in nutrients, high in productivity, high in organic matter, low in light
penetration, and high in numbers of organisms.
At first glance a Eutrophic lake may appear to be a healthy lake based upon high productivity.
However, lakes that are eutrophic tend to decline in time so that fish populations become very
low and the lake may eventually die. To the public an Oligotrophic lake may be ideal for
swimming because the water quality may be very good, but at the same time, this type of lake
may have very few organisms present. Somewhere in the middle, a balanced lake exists.
Shannon and Brezonik (1972) developed a system for measuring the trophic status of a
lake. They developed an index that incorporates seven indicators: primary productivity,
conductivity, chlorophyll a, total phosphorus, total organic nitrogen, Secchi depth, and the ration
of monovalent (sodium and potassium) to divalent (calcium and magnesium) cations. Other
systems have been developed that modify the index for regional differences.
Nutrient data for more than 500 lakes in Florida is available. The nutrient status of the
lakes runs from very oligotrophic to hyper-eutrophic (lakes near phosphate mines, muck farms,
and sewage plants). Some lakes are very pristine, while others are loaded with nutrients and
toxins (Lake Apopka). However, most of the lakes in Florida are in the oligotrophic to
The plants in a lake form the ecological foundation for productivity and stability of the
system. The plants found in lakes come in three groups:
Emergent: these are the plants that grow at the edge of a lake, i.e. they “emerge” from
the water’s edge. They reproduce rapidly and overgrow other plants at the edge. There is
intense competition among the plants in this ecological zone.
Floating Plants: these are the plants that float on the water’s surface.
Submergent: these are the plants hat anchor to the bottom of the lake and grow upward.
Estuaries are ecological systems that are influenced by tides where rivers and
streams meet the sea and fresh water mixes with salt water.
As ecological systems estuaries provide the following:
Habitat: Tens of thousands of birds, mammals, fish, and other wildlife
depend on estuaries.
Nurseries: Many marine organisms of commercial value depend on estuaries
at some point during their development.
Productivity: A healthy estuary produces from four to ten times the weight of
organic matter produced by a cultivated cornfield of the same size. They are
among the most productive ecosystems on earth.
Water filtration: Water draining off the uplands carries a load of sediments
and nutrients. As the water flows through salt marshes and the dense mesh of
marsh grass blades, much of the sediment and nutrient load is filtered out.
This filtration process creates cleaner and clearer water.
Flood control: Porous, resilient salt marsh soils and grasses absorb
floodwaters and dissipate storm surges. Estuaries provide natural buffers
between the land and the ocean. They protect upland organisms as well as
billions of dollars of human real estate. Estuaries are crucial transition zones
between land and water.
Fairbridge presented a more inclusive and precise definition of an estuary in 1980 as follows:
An estuary is an inlet of the sea reaching into a river valley as far as the upper limit of
tidal rise, usually being divisible into three sections:
(a) A marine or lower estuary with a free connection to the sea
(b) A middle estuary subject to strong salt and freshwater mixing.
(c) An upper or fluvial estuary characterized by fresh water but subject to tidal
The limits between these sectors are variable and subject to constant changes in the river
Ecology of estuaries:
Productivity in an estuary comes from the plants and the phytoplankton that inhabit the
system. Since the estuaries in Florida have warm weather for most of the year, production occurs
for most of the year. Abundant nutrients flow out of the rivers and streams into the bay,
nourishing the plants, especially in the rainy season (July through September). The
phytoplankton of an estuary are abundant and highly productive.
Phytoplankton remove carbon dioxide (CO2) from the water, and with the use of sunlight,
convert the carbon into useable biomass (body mass). The concept of "production" comes from
the ability of organisms to convert carbon dioxide into biomass. The more biomass they produce
the more productive the organisms are. In the same sense, the more production that is taking
place among the phytoplankton, the more productive the ecosystem is. Estuaries are considered
to be one of the most productive ecosystems on earth for a variety of reasons. Primarily, estuaries
have light, moving currents, and abundant nutrients from the streams and rivers that flow in. This
combination results in very high growth rates for the phytoplankton, and the start of a very active
food web for other organisms within the estuary.
The complexity of the species composition was highlighted in a study decades ago. In
this study conducted in Tampa Bay from 1972 to 1975, a total of 46 dinoflagellate species, 137
diatom species, and 3 cyanobacteria species were identified in the bay. Sometimes, as many as 5
species of phytoplankton may be blooming in the bay at the same time.
Phytoplankton typically comes in four basic types:
1. Dinoflagellates: these are typically single celled photosynthetic organisms that
build protective walls made of interlocking cellulose plates. Each has two flagella
to aid them in movement.
2. Diatoms: these are single celled photosynthetic organisms that build protective
walls around themselves made of silicon. Their cell walls are composed of two
halves that fit together.
3. Phytomicroflagellates: these are small photosynthetic protists that can propel
themselves through the water by means of a whip-like tail known as a flagellum.
4. Cyanobacteria: these were once called blue-green algae, but now are placed
with bacteria because of the nature of their cell structure, which is bacterial. These
are photosynthetic bacteria that may be single celled or multi-celled in colonies,
containing chlorophyll in the same manner as plants but may have accessory color
pigments to give them a variety of colors. In excessive numbers in an estuary,
they would be considered an indicator of nutrient over-load for the system.
The plants of an estuary are typically the seagrasses, algae, and emergent vegetation, like
mangroves, Spartina and Juncus. Again, the nutrients flowing out of the rivers and streams spur
growth of the plants. In addition, the estuarine plants receive nutrients from the sediment, which
is usually anaerobic. The nutrients in the sediment come from decomposition and from bacteria.
The factors that affect productivity are: temperature, sunlight, evapotranspiration, tides, salinity,
rainfall, nutrient loading and circulation patterns.
The second trophic level is composed of zooplankton and a variety of algae eaters, like
Mullet and blue crabs. The zooplankton feed on the phytoplankton and other zooplankton. The
mullet and blue crabs wander through the estuary eating algae and some plants. Some have
speculated that the increases in algae in estuaries is not only the result of nutrient loading in the
bay, but also a loss of mullet and blue crabs due to commercial harvesting pressure. If the second
level of the trophic level declines, the first level increases - fundamental ecology.
In the third and fourth trophic levels the larger predators of the estuary feed upon the
smaller members. The organisms at this level may be those that move in from the salt water,
those that move in from the freshwater or those that live out their lives in the estuary. Note the
diagram below that shows how salinity is the main barrier of movement of organisms through
the ecosystem. The majority of organisms found in the bay will be those from the salt-water
environment. They typically move into the bay at high tide. As the tides recede, the freshwater
organisms move into the bay. This process repeats at every change in tide. The organisms in the
middle, those that tolerate the changes in salinity, are few in number.
The movement of fish to and from the bay is much more complicated than a simple effort
of fish to find food or to reproduce. Consider the following patterns:
1. Some fish spend their entire lives in the bay.
2. Some fresh water fish occasionally enter brackish water.
3. Some marine species use the bay as a nursery ground, but may return seasonally to the
bay for feeding.
4. Some marine fish regularly visit the bay during a certain season, most often looking
5. Some fish come from the Gulf to the bay to reproduce; others come from fresh water
to the bay to reproduce. In either case they only visit the bay to reproduce. Most
reproduction of fish in Tampa Bay occurs in the spring with a second smaller
reproductive period in the fall. Following spawning, many of the larval fish migrate to
the shallow protected waters of the bay.
6. Some fish are just occasional visitors to the bay.
From this discussion, it is apparent that the movement of fish in the bay is not subjective. There
are a number of variations.
Some of the fish that can survive within the bay despite changes in salinity are as follows:
Pinfish (Lagodon rhomboides)
Bay Anchovy (Anchoa mitchilli)
Tidewater Silverside (Menidia peninsulae)
Silver Jenny (Eucinostomus gula)
Spotfin Mojarra (Eucinostomus argenteus)
Pigfish (Orthopristis chrysoptera)
Longnose Killifish (Fundulus similis)
Goldspoted Killifish (Floridichthys carpio)
Redfish (Sciaenops ocellata)
Striped Mullet (Mugil cephalus)
Sheepshead minnow (Cyprinodon variegates)
Facts about some of Florida’s estuaries:
The following information about estuaries is primarily from the National Estuary Program
The Apalachicola Reserve includes two barrier islands and a portion of a third. The
Reserve also includes the lower 52 miles of the Apalachicola River and its associated
floodplain, small portions of adjoining uplands, and the Apalachicola Bay system. The
overall high water quality of the Apalachicola estuary, with the combined effects of other
factors, provide the ideal living conditions for estuarine biota and have resulted in the
creation of a highly productive estuarine system. The myriad of habitats found within the
Reserve support a wide range of plant and animal species, many of which are threatened
The Apalachicola Reserve is the second largest of the twenty-five currently existing
national estuarine research reserve sites, with 246,766 acres of land and water within its
boundaries, and potential for considerable expansion.
The Apalachicola River Basin is only part of the larger Apalachicola-Chattahoochee-Flint
(ACF) River system. The ACF basin covers the north-central and southwestern part of Georgia,
the southeastern part of Alabama, and the central part of the Florida panhandle. Its drainage
basin encompasses approximately 19,600 square miles.
The Apalachicola River, the largest river in Florida, in terms of flow, is formed by the
confluence of the Chattahoochee and Flint rivers and flows 107 miles to Apalachicola Bay. It
drains a land area of approximately 2,400 square miles in Florida. The importance of the
Apalachicola River to the productivity of the Bay cannot be overemphasized. The Chattahoochee
River flows 436 miles from its source in the Blue Ridge Mountains of northern Georgia, drains a
land area of 8,650 square miles, and has 13 dams located on the river. The Flint River flows 350
miles from its source south of Atlanta, drains a land area of 8,494 square miles, and has 2 dams
affecting stream flow. The last dam on the system is located where the Chattahoochee and Flint
Rivers meet, above the beginning of the Apalachicola River.
Tampa Bay, Florida's largest open-water estuary stretches 398 square miles at high tide.
Popular for sport and recreation, the bay also supports one of the world's most productive natural
systems. Estuaries like Tampa Bay, where salt water from the sea and fresh water from rivers
and uplands mix, are nurseries for young fish, shrimp, and crabs. More than 70 percent of all
fish, shellfish, and crustaceans spend some critical stage of their development in these near shore
waters, protected from larger predators that swim the open sea.
Wildlife abounds along the shores of Tampa Bay. As many as 40,000 pairs of birds--from the
familiar brown pelican to the colorful roseate spoonbill--nest in Tampa Bay every year. Others,
including sandpipers and white pelicans, are seasonal visitors. The bay is also home to dolphins,
sea turtles, and manatees.
1. Tampa Bay is the largest open-water estuary in Florida, encompassing nearly 400 square
miles and bordering three counties -- Hillsborough, Manatee and Pinellas. The bay's
sprawling watershed covers a land area nearly five times as large, at 2,200 square miles.
2. More than 100 tributaries flow into Tampa Bay, including dozens of meandering,
brackish-water creeks and four major rivers -- the Hillsborough, Alafia, Manatee and
3. A single quart of bay water may contain as many as 1 million phytoplankton --
microscopic, single-celled plants that are an essential thread in the "who eats who"
marine food web.
4. More than 200 species of fish are found in Tampa Bay, including the popular snook,
redfish and spotted sea trout.
5. Mangrove-blanketed islands in Tampa Bay support the most diverse colonial water bird
nesting colonies in North America, annually hosting 40,000 pairs of 25 different species
of birds, from the familiar white ibis and great blue heron to the regal reddish egret -- the
rarest heron in the nation.
6. Each square meter of bay sediment contains an average of 10,000 animals -- mostly tiny,
burrowing worms, crustaceans and other mud-dwellers that are known as benthic
invertebrates. The most numerous animal in the bay sediment is a primitive, fish-like
invertebrate about two inches long called branchiostoma.
7. On average, Tampa Bay is only 12 feet deep. Because it is so shallow, manmade shipping
channels have been dredged to allow large ships safe passage to the Port of Tampa and
other bay harbors. The largest of these, the main shipping channel, is 43 feet deep and 40
8. The Port of Tampa is Florida's largest port and consistently ranks among the top 10 ports
nationwide in trade activity. It contributes billions annually to the region's economy.
9. More than 4 billion gallons of oil, fertilizer components and other hazardous materials
pass through Tampa Bay each year.
Located on the west coast of peninsular Florida, Charlotte Harbor is the second largest
open water estuary in the state. The basins of the Peace, Myakka, and Caloosahatchee Rivers
(almost 4,500 square miles) feed freshwater into the coastal area. In southwest Florida, barrier
islands and coastal waters such as Lemon Bay, Matlacha Pass, Pine Island Sound, Charlotte
Harbor, and Estero Bay are supplied with freshwater from those three rivers and nearby areas.
The Charlotte Harbor estuary and contiguous coastal waters serve as a home, feeding ground
and/or nursery area for more than 270 species of resident, migrant, and commercial fishes of the
Gulf of Mexico. Manatees, sea turtles, wood storks, and dolphins are also found in the estuary
and its watershed. This estuarine system and its watershed are both directly and indirectly a
vitally important economic asset to the Florida Suncoast. This NEP's addition to the program was
announced on July 6, 1995.
The Charlotte Harbor National Estuary Program challenges local communities to address
water quality, wildlife habitat loss, land use changes, and human-induced changes to river flow
to protect uses of the estuary. The population within the watershed is projected to reach 1.7
million by the year 2010, a 337 percent increase over the 1970 census. This rapid growth has
already radically changed the character and ecology of river mouth and coastal waters.
Mangroves have been removed or cut back, red tide events cause public health warnings,
seagrass areas have declined or been damaged, and groundwater pumping has reached its
maximum limit. Despite these impacts, the main body of Charlotte Harbor and its adjacent
estuarine systems are in comparatively good condition.
Much of Sarasota Bay's habitat for young fish was destroyed as the natural; mangrove
shoreline was replaced by concrete sea walls during development of waterfront communities. As
a result, the Sarasota Bay Program, in addition to wetland restoration, is embarking on an
artificial habitat enhancement strategy to increase its young fish population and overall fishery
production. Since most of those sea walls cannot be removed without causing severe damage to
homes, a project by the Sarasota Bay NEP may turn those sea walls in to an asset for the bay,
rather than a liability. Four different styles of small artificial reefs attached to sea walls are being
tested for their ability to provide a home for young fish. Early results show more than 400 young
fish living near the reefs. Only a few young fish have been seen in similar areas without reefs.
The Comprehensive and Conservation Management Plan (CCMP) encompasses several
approaches: Reforming seawalls, shoreline softening, bay bottom improvements and channel
markers as habitat. Different styles of artificial modules and engineering options will be utilized
along with baseline and follow-up monitoring studies.
The coral reefs of Florida are one of the most diverse ecosystems on our planet, rivaling
even that of tropical rain forests. Built over thousands of years by tiny calcium-producing
organisms, the reefs are a refuge for thousands of creatures, some of which seem totally alien in
form. It is an underwater world of bright colors and ever changing patterns. Only on the reef can
one find living examples from nearly every group of organisms representing hundreds of
millions of years of evolution. Coral reefs are among the most ancient of ecosystem types, dating
back to the Mesozoic era some 225 million years ago. Modern reefs can be as much as 2.5
million years old.
The reefs of Florida are an extremely fragile environment, and are in very real danger of
disappearing forever. Mankind's ignorance and carelessness is beginning to have a noticeable
impact on the world's reefs. From the Florida Keys to the Great Barrier Reef in Australia, the
damage is becoming apparent.
Most of the coal reefs of Florida are found in the Florida Keys; however, some reefs are
found along the Atlantic Coast as far north as Daytona Beach. The reefs off of Daytona lie in
water about 20 meters deep and 10 to 15 miles off shore. There are reefs along the Gulf Coast as
well. They lie scattered along the floor of the Gulf of Mexico as far north as Cedar Key and as
deep as 35 meters.
Although they cover only a tiny fraction (less than 0.2%) of the ocean's bottom, coral
reefs capture about half of all the calcium flowing into the ocean every year, fixing it into
calcium carbonate rock at very high rates. Coral reefs release carbon dioxide to the atmosphere
by means of calcium carbonate precipitation. The release of carbon dioxide from coral reefs is
very small (probably less than 100 million tons of carbon per year) relative to emissions due to
fossil fuel combustion (about 5.7 billion tons of carbon per year).
Classification of Corals
This diverse invertebrate phylum includes corals, sea anemones, hydras, jellyfishes, and
their relatives. All cnidarians are radially symmetrical (the body is symmetrical around a central
axis), lack a head, usually have a crown of tentacles around the mouth, and possess nematocysts.
About 9,000 living species are known.
1. Anthozoans include corals, sea anemones, sea pens, and sea pansies. These animals are
either solitary or colonial polyps that live attached to a substrate (surface). Of the 6,000
known anthozoan species, corals comprise about 2,500 species.
2. The Class Anthozoa is further divided into three subclasses: Octocorallia, Zoantharia,
and Tabulata (extinct colonial corals).
a. Subclass Octocorallia. Polyps are characterized by having eight pinnate (side-
branching) tentacles. Octocorallians include gorgonian corals, sea pens, sea
pansies, organ- pipe corals, and soft corals (order Alcyonacea). Most are colonial.
b. Subclass Zoantharia. Polyps are characterized by having tentacles in multiples
of six. Zoantharian tentacles are rarely pinnate. Black corals and reef-building
corals (order Scleractinia) are members of this subclass. Reef-building corals are
also known as "hard corals" or "stony corals." Zoantharians may be either solitary
c. Subclass Tabulata. Extinct colonial corals.
1. Although various types of corals can be found from the water's surface to depths of
6,000 meters, reef- building corals are generally found at depths of less than 46 meters,
where sunlight penetrates. Because reef- building corals have a symbiotic relationship
with microscopic algae (zooxanthellae), sunlight is necessary for these corals to thrive
a. Reefs tend to grow faster in clear water. Clear water allows light to reach the
symbiotic algae living within the coral polyp's tissue. Many scientists believe that
zooxanthellae promote polyp calcification. b. Light-absorbing adaptations enable
some reef- building corals to live in dim blue light.
2. Reef-building corals require warm ocean temperatures (68 to 82 F, or 20 to 28 C).
Warm water flows along the eastern shores of major landmasses.
3. Reef development is generally more abundant in areas that are subject to strong wave
action. Waves carry food, nutrients, and oxygen to the reef; distribute coral larvae; and
prevent sediment from settling on the coral reef.
4. Precipitation of calcium from the water is necessary to form a coral polyp's skeleton.
This precipitation occurs when water temperature and salinity are high and carbon
dioxide concentrations are low. These conditions are typical of shallow, warm tropical
5. Most corals grow on a hard substrate.
Coral reefs are found throughout the world in tropical, clear shallow water. The following
map shows the locations of the world’s coral reefs. Coral reefs are generally found within 30*N
and 30*S latitudes. One exception is Bermuda, which lies in the path of the Gulf Stream. The
stream brings the island warm clear water from the south.
Reef map from “Reef World”
Types of reefs:
The following is a description of the types of reefs found in the world.
Barrier Reefs - Barrier reefs are reefs that are separated from land by a lagoon. These
reefs grow parallel to the coast and are large and continuous. Barrier reefs also include
regions of coral formation that include the zones found in fringing reefs along with patch
reefs (small reefs), back reefs (the shoreward side of the reef), as well as bank reefs (reefs
that occur on deep bottom irregularities). Barrier reefs also include reef flats (areas of the
reef not exposed), the reef crest, which runs parallel to the coast and is protected from
waves, and a coral terrace (a slope of sand with isolated coral peaks).
Atolls - Atolls are annular reefs that develop at or near the surface of the sea when
islands that are surrounded by reefs subside. Atolls separate a central lagoon and are
circular or sub-circular. There are two types of atolls: deep-sea atolls that rise from deep
sea and those found on the continental shelf.
Corals can obtain food in a variety of ways. Reef-building corals rely on the
photosynthetic products of zooxanthellae for the majority of their nutrients. Zooxanthellae are
unicellular yellow-brown (dinoflagellate) algae that live symbiotically in the gastrodermis of
reef-building corals. Zooxanthellae of various corals have been found to belong to at least 10
different algal taxa. Interestingly, zooxanthellae found in closely related coral species are not
necessarily closely related themselves, and zooxanthellae found in distantly related coral species
may, in fact, be closely related. This suggests that coral and zooxanthellae evolution did not
occur in permanently associated lineages. Rather, symbiotic recombination probably shaped the
evolutionary process, allowing both symbionts to evolve separately.
Corals also capture zooplankton for food. Corals are also suspension feeders. They
utilize two main methods of prey capture: nematocyst adhesion and mucus entrapment.
Nematocysts are small “stingers” on the tentacles. They can be used to sting prey and move it
into the mouth. Some corals will trap prey in sticky mucus on their tentacles and move the prey
into the mouth using the mucus and cilia.
Most corals feed at night. This may be because night is when the zooplankton travel into
the water column and become available for capture. Keeping the tentacles retracted during the
day may also help corals avoid predation, protect themselves from UV light, and avoid shading
Corals exhibit sexual and asexual reproduction. The coral colony expands in size by
budding. Budding may be intra-tentacular, in which the new bud forms from the oral discs of the
old polyp, as in Diploria, or extra-tentacular in which the new polyp forms from the base of the
old polyp, as in Montastraea cavernosa.
A common type of asexual reproduction in corals is by fragmentation. Broken pieces of
corals that land on a suitable substrate may begin growing and produce a new colony. This type
of reproduction is common in branching corals like Acropora cervicornis in which a positive
correlation was found between fragment size and survival.
Many coral species spawn at the same time in one large mass of sperm and egg in the
water column. Within a 24-hour period, all the corals from one species and often within a genus
release their eggs and sperm at the same time.
Some species of coral brood their larvae. The sperm fertilizes the egg before both are
released from the coral. The larvae float to the top, settle, and become another colony. Species of
Acropora release brooded larvae.
Coral reefs are among the most endangered ecosystems on earth. Coral reefs in 93 of the
109 countries containing them have been damaged or destroyed by human activities. In addition,
human impacts may have directly or indirectly caused the death of 5-10% of the world's living
reefs, and if the pace of destruction is maintained, another 60% could be lost in the next 20-40
The most important short-term threats to coral reefs are sedimentation (from poor land
use such as clear-cutting on steep slopes and other activities such as dredging without silt
curtains), eutrophication (over-fertilization caused by excessive fertilizer use and sewage
pollution), and over fishing. Destructive fishing techniques such as fine mesh nets, cyanide
poisoning, and dynamiting are common in coral reefs, and have actually come to dominate
fishing in parts of Indonesia and the Philippines.
Physical damage to coral reefs by scuba divers and tourists would probably be a minor
threat if the number of visitors to reefs were limited to moderate levels and if water quality was
always high enough to support rapid recovery of corals. However, tourism often results in large
numbers of visitors, which leads to extensive physical damage, sewage pollution, and other
adverse water quality impacts that slow or eliminate recovery.
Coral reefs in every major tropical region of the world bleached white during the mass
bleaching events of the 1980's. This bleaching depresses coral growth rates and in some cases
results in mass coral mortality and enormous aquatic population loss, and can even contribute to
potential species extinctions. Bleaching is caused by a variety of factors, including siltation and
changes in salinity resulting from poor land use, pollution, and slight increases in temperature.
Coral reefs may bleach even more extensively if global warming continues unabated.
Florida has thousands of springs that range in size from a flow of a few gallons a year to
those that produce millions of gallons of water per day. In this last category, Florida has 78
springs that have an average discharge of over 100 cubic feet per second (classified as magnitude
1 springs by the USGS). The fastest spring in Florida is Spring Creek in Wakulla County that
pours out 2,000 cubic feet per second. The total flow from all of Florida’s springs may exceed 8
billion gallons of water per day.
A spring is a site where water flows from a natural leakage or overflow from an aquifer through
a natural opening in the ground. The openings may be very large and create significant flow of
water resulting in the creation of a river, or they may be very tiny just seeping water to the
surface. Some springs have significant chemical characteristics, such as sulfurous or salty,
sodium bicarbonates, chlorides, sulfates, hardness, calcium and magnesium. Many chemical
variances exist among the springs of Florida. A constant environmental factor for springs is their
stable temperature. Most springs keep their temperatures within a range of less than 10 degrees
throughout the year.
The water flowing out of the springs comes from the Florida aquifer system. The aquifer system
is a series of underground caverns dating back to the tertiary age that are filled with water. The
water in the aquifers flows constantly under the state, often to the surface for discharge into a
spring. Most of the springs are concentrated on the west coast of the state.
Whitford (1965) presented the following classification of springs in Florida:
Soft – freshwater: these are freshwater springs that contain few minerals.
Hard – freshwater: these are freshwater springs that have high levels of minerals. Silver
Springs is an example.
Oligohaline: these springs contain chlorides in the water in the range up to 600 mg/kg.
Homosassa Springs is an example.
Mesohaline: these have mid ranges of chlorides from about 600 to 9,000 mg/kg.
Sulfide: springs that contain high levels of sulfates and/or sulfides.
Salt / sulfide: these springs contain both salts water and sulfides. An example is Warm
Mineral Springs that has high levels of chlorides and sulfides as well as a high
temperature. No aquatic flowering plants can live in this spring.
Spring communities are characterized by relatively small numbers of species. In the following
sections some of the species will be discussed.
Water flow in springs:
The normal flow of water in springs is controlled by hydrologic and geologic factors,
such as amount and frequency of rainfall, the porosity and permeability of the aquifer, the
hydrostatic head (pressure) within the aquifer, the hydraulic gradient. Artesian springs are
influenced by atmospheric pressure systems and oceanic tides. The flow of springs is also
changed, usually decreased, by man through means as pumping from wells that tap the aquifer.
Florida has sufficient rainfall to keep its aquifers recharged sufficiently to maintain
perennial flow at most artesian springs. Though the State does experience water-supply problems
in some areas where ground-water withdrawal is excessive, this condition is the exception, and
variations in discharge rates of artesian springs have been remarkably small. However, in the late
1990’s water withdrawal from the aquifer in Pasco County and northern Hillsborough County
did result in the drying up of many springs and lakes. The flows of large springs may be
substantial even through periods of drought; this is understandable when the large volume of
water stored in Florida's artesian aquifer system is compared with the relatively small discharge
of its springs. The total discharge from all the artesian springs is not enough to deplete the
aquifer between periods of recharge. On the other hand, the variations in flow of water-table
springs may be great in response to rainfall variations and may cease flowing in the dry season
be- cause of the relatively small size and low storage capacity of many water- table aquifers.
Plants and Productivity
Primary production in Florida’s spring comes, as in most ecosystems, from plants and
algae. Some of the aquatic plants found in springs in Florida are
Sagittaria spp (arrowheads and eelgrass)
Vallisneria Americana and spiralis (Tape grass)
Chara spp (muskgrass)
Myriophyllum heterophyllum (milfoil)
Najas guadalupensis (southern naiad)
Nasturtium officinale (watercress)
Pistia stratiodes (water lettuce)
Zizania aquatica (wild rice)
Odum in 1957 compared productivity in several of Florida’s springs. The data from his study are
shown in the chart:
Rates of gross primary productivity in Florida Springs
Spring Community GPP (g C m-2 day-1
Beecher (anoxic spring) 0.26
Blue (Alachua County) 1.95
Blue (Alachua County) – Utricularia 0.75
Blue (Volusia County) 2.03
Weeki Wachee 4.01
Green Cove 5.81
The variances noted among the springs for productivity were due to shading, nutrient loading,
types of vegetation, N/P ratio, depth of water, carbon dioxide levels, and oxygen levels.
According to this study, the primary cause of productivity variance was due to light availability.
The springs of Florida have a variety of fish; both fresh and salt water species. Some of
the most common species found in springs are:
o Strongylura marina (Atlantic needlefish)
o Mugil cephalus and curema (mullet)
o Dasyatis sabina (stingray)
o Tarpon atlanticus (Tarpon)
o Galeichthys felis (catfish)
o Centropomis undecimalis (snook)
o Lutjanus griseus (mangrove snapper)
o Sciaenops ocelatus (redfish)
o Cynoscion nebulosis (seatrout)
o Caranx hippos (jack)
o Dorosoma cepedianum (Shad)
o Micropterus salmoides (Largemouth bass)
o Lepomis Macrochirus (Bluegill
o Pomoxis annularis (White crappie)
Along the coasts of Florida, salt marshes are the bridges between the sea and the land.
They are very productive systems that are essential to many important species in Florida
Salt marshes border the large shallow bays and estuaries where inland rivers empty into
the sea. Tidal creeks meander through them, rising and falling twice a day, flooding the marsh,
and then retreating. From a distance, salt marshes look like broad, flat, treeless meadows covered
with waving grasses and open expanses of sand and salt.
Despite their ecological importance, nearly half of all Florida's marshes, both saltwater
and freshwater, have been lost to development, dredging, and mosquito control impoundments
during the past 100 years.
Some salt marshes are nontidal, many are impounded, and their structure and
composition is dynamic due to water level management and geographic location. Salt marshes
are dominated by almost pure stands of Spartina alterniflora, cordgrass (S. bakerii), black rush
(Juncus roemerianus), salt grass (Distichlis spicata), and other salt tolerant grasses. Many salt
marshes are comprised of shrub-sized mangroves, Batis maritima, Salicornia spp., and salt grass.
Historically in Florida, salt marsh landscapes were not flooded for most of the year
except for scattered creeks and ponds. A large number of endangered and potentially endangered
species require or at least use salt marsh habitat. Some are specialized to use low salt tolerant
vegetation, others require mangroves, and others require open water within the habitat. The most
likely locations for the Atlantic Salt Marsh Snake, if they are present, are salt marshes dominated
by Salicornia, Batis maritima and salt grasses along the east shore of Mosquito Lagoon. Salt
marshes along the St. Johns River once provided habitat for the extinct Dusky Seaside Sparrow.
Impoundment, fires, highway construction, and other activities contributed to its extinction. The
Black-whiskered Vireo and Florida Prairie Warbler are dependent on mangrove vegetation. The
dynamics of these populations are uncertain, especially during cold winter months. The Black-
whiskered Vireo still is common in a few areas and Florida Prairie Warblers can be heard singing
in spring on some spoil islands where there are few or no mangroves. Salt marsh vegetation is
important to Least Bitterns. The Black Rail is very dependent on low salt marsh vegetation such
as Distichlis and Salicornia. The species was once a common breeding bird prior to
impoundment. Impoundment was detrimental to rails, but this effect was not quantified. Clapper
Rails (Rallus longirostris) are still common along edges of salt marshes in impoundments. The
Round-tailed Muskrat is also abundant in some marshes dominated by salt grass.
Salt marsh food chain
The foundation of the salt marsh food chain is the grasses, and the grasses derive their
energy from the sun through photosynthesis. The overall food web for the marsh is a detrital
based food web. Many other ecosystems are based on the model where primary consumer or
herbivore is eaten by secondary consumer, is eaten by tertiary consumer, etc. In the salt marsh,
most of the primary production (the grasses) is not passed directly to herbivore through grazing,
but rather the grasses enter the food web after becoming enriched as detritus. It has been
estimated that between 45 and 60% of the organic matter initially in the grasses enters the detrital
food web, the rest being eaten by herbivores. The detritus is said to be enriched because the
action of microorganisms, particularly bacteria, breaks down the plant cellulose and add their
own protoplasm to the mix. The interrelationships among producers, decomposers and
consumers in the marsh are very complex. Even researchers using complex computer-based
models have been unable to completely diagram the complexity of the salt-marsh food web. It is
clear, however, that all of the various parts of the marsh are interdependent upon one another.
The Juncus community
Georgia field of Juncus roemerianus (Black Needlerush)
Black Needlerush is an important plant in the seaside habitat, inland from the Spartina
growths. This plant is a tall slender grass-like plant that has narrow leaves that emerge at the top
in a sharp point. These points can easily puncture the skin of persons walking among the plants.
The Juncus community is usually found more shoreward from the Spartina community
and is in areas that are irregularly flooded with salt water at the highest of high tides. At low
tides the community is flooded with fresh water from nearby rivers and streams. It is, therefore,
on the fringe of the brackish water embayment.
On occasion Juncus communities can be intermixed with Spartina communities, but
more often the two communities maintain distinct boundaries. The Spartina community is
usually found in more salty shorelines than that of the Juncus community.
Black Needlerush communities are usually monotypic stands (one species only) and they are
often the most productive of the seaside plant communities. The high productivity comes from
one very important reason. The Juncus roemerianus plant is an evergreen. This means that the
plants can maintain productivity throughout the year, while other plants of the shoreline and
embayments will slow (or stop) productivity during the winter months. The Juncus community
manages to equal or exceed the annual net production of most ecosystems.
The Spartina community
Spartina alterniflora (smooth cordgrass)
Smooth cordgrass looks like a typical "grass" having long thin shoots that grow upward
from the sediment. It has a prominent ecological importance in its location along the shoreline.
One of the more important roles is its ability to stabilize the shore. The roots hold the sediment in
place and prevent it from washing out to sea. Because of this role, smooth cordgrass is often
planted along new shorelines that are created for highways and bridges. Another role for
cordgrass is that it is home for many organisms. While walking along the shoreline in the grasses
two organisms are readily apparent: the sand fiddler crab (Uca pugilator) and the marsh
periwinkle (Littorina irrorata).
The sand fiddler crab is often found by the thousands along the shorelines of Tampa Bay.
The crab has a body almost 3/4 of an inch wide, and is white with a pink patch in the center of
the back. The claws are light in color, often with a pale orange coloring underneath. Male fiddler
crabs have one claw larger than the other. The males use this over-sized claw to signal
aggression against other males, or they use it to attract females. The pattern by which they
display their claw is a distinct signal to other crabs. The ritualistic movement of the claw is a
sexual attractant to the female. Once they are seduced by the movement they move into a burrow
with the male to reproduce. Females lack the larger claw, but otherwise are quite similar to the
males. The fiddler crabs live in small burrows along the shoreline, from which they scurry about
the flats looking for food. Their activities are related to the tides, with their greatest activities
occurring during low tide. This is when they are most active.
The marsh periwinkle is a small attractive snail that clings to the blades of cordgrass. It
moves up the blades of the cordgrass when the tides are high, and moves down the blades when
the tides are low. If the tides recede from the grasses, then the snail will crawl about the mud
Wetlands are land depressions where water inundates the soil for periods of time from a
few weeks to an entire year. The saturation of the soil (hydric) ultimately determines the species
of plants that will grow in the region. Only certain species of plants can survive within the
confines of a wetland (hydrophytes); however, some terrestrial plants do survive along the
margins, and sometimes, within the wetland. Therefore, most wetlands support both aquatic and
There are variations in wetlands from one location to another, and from region to region
based upon variances in climate, hydrology, landscape, water chemistry, and many other factors.
The common types found in Florida are: Cypress swamps, freshwater marshes, salt marshes,
hardwood swamp, Everglades, etc.
The USFWS classification system for wetlands gives the following:
In 1979, a comprehensive classification system of wetlands and deepwater
habitats was developed for the U.S. Fish and Wildlife Service (Cowardin et al. 1979).
Under this system, wetlands are of two basic types: coastal (also known as tidal or
estuarine wetlands) and inland (also known as non-tidal, freshwater, or palustrine
Coastal wetlands are found along the Atlantic, Pacific, Alaskan, and Gulf coasts
and include estuaries. The salt water and tides combine to create an environment in which
most plants, except salt-tolerant species (halophytes), cannot survive. Mangrove swamps,
dominated by halophytic shrubs or trees, are common in warm climates, for example, in
southern Florida, Puerto Rico, and Louisiana. Tidal freshwater wetlands form in upstream
coastal wetlands where the influence of salt water ends.
Inland wetlands include floodplains along rivers and streams (e.g., bottomlands
and other riparian wetlands); isolated depressions surrounded by dry land (e.g., prairie
potholes); areas where the groundwater intercepts the soil surface (e.g., fens) or where
precipitation saturates the soil for a season or longer (e.g., vernal pools and bogs).
Grasses and other herbaceous plants or shrubs dominate Marshes and wet meadows; and
swamps are dominated by trees.
The USFWS's Cowardin classification system defines deepwater habitats are
defined as: permanently flooded lands lying below the deepwater boundary of wetlands
(2 meters), including environments where surface water is permanent, with water, rather
than air, the principal medium within which the dominant organisms live.
The Cowardin system is hierarchical and includes several layers of detail for
wetland classification including: a subsystem of water flow; classes of substrate types;
subclasses of vegetation types and dominant species; as well as flooding regimes and
salinity levels for each system. This system is appropriate for an ecologically based
understanding of wetland definition.
Cowardin Wetland and Deepwater Systems
The following is a brief description of the major classes of wetlands under the Cowardin
Marine - Open Ocean overlying the continental shelf and coastline exposed to
waves and currents of the open ocean shoreward to
(1) extreme high water of spring tides;
(2) seaward limit of wetland emergents, trees, or shrubs; or
(3) the seaward limit of the Estuarine System, other than vegetation. Salinities
exceed 30 parts per thousand.
Estuarine - Deepwater tidal habitats and adjacent tidal wetlands that are usually
semi-enclosed by land but have open, partly obstructed, or sporadic access to the
ocean, with ocean water at least occasionally diluted by freshwater runoff from
the land. The upstream and landward limit is where ocean-derived salts measure
less than .5 parts per thousand during the period of average annual low flow. The
seaward limit is
(1) an imaginary line closing the mouth of a river, bay, or sound; and
(2) the seaward limit of wetland emergents, shrubs, or trees when not included in
Riverine - All wetlands and deepwater habitats contained within a channel except
those wetlands (1) dominated by trees, shrubs, persistent emergents, emergent
mosses, or lichens, and (2) which have habitats with ocean-derived salinities in
excess of .5 parts per thousand.
Lacustrine - Wetlands and deepwater habitats
(1) situated in a topographic depression or dammed river channel;
(2) lacking trees, shrubs, persistent emergents, emergent mosses, or lichens with
greater than 30% areal coverage; and
(3) whose total area exceeds 8 hectares (20 acres); or area less than 8 hectares if
the boundary is active wave-formed or bedrock or if water depth in the deepest
part of the basin exceeds 2 m (6.6 ft) at low water. Ocean-derived salinities are
always less than .5 parts per thousand.
Palustrine - All nontidal wetlands dominated by trees, shrubs, persistent
emergents, emergent mosses, or lichens, and all such tidal wetlands where ocean-
derived salinities are below .5 ppt. This category also includes wetlands lacking
such vegetation but with all of the following characteristics:
(1) area less than 8 ha;
(2) lacking an active wave-formed or bedrock boundary;
(3) water depth in the deepest part of the basin less than 2 m (6.6 ft) at low water;
and (4) ocean-derived salinities less than .5 parts per thousand.
A Palustrine system can exist directly adjacent to or within the Lacustrine,
Riverine, or Estuarine systems
Delineation of Wetlands
Many systems have been developed to determine the extent, boundaries and physical
characteristics of wetlands. Although each classification system relies upon some unique aspect
of wetlands, they all use the following characteristics:
Aquatic Plants: the identification of aquatic plants found in a wetland are classified and
measured. The presence of aquatic plants in a location that is potentially a wetland is a
strong indicator of water inundation.
Facultative wet plants (FACW): these are plants that may be found in upland areas, but
are more likely found in low areas (wetlands) that have frequent inundation.
Hydric soils: the measurement of the soils in a wetland. Soils are telltale signs of the
boundaries of a wetland. In addition, the saturation of the soil with water is also a good
Obligate plants: are those plants that are only found in areas that are subject to surface
water inundation. Identification of these plants within an area is a clear indicator of a
Saturation: the extent to which water tables can create anaerobic conditions in the soil
profile. Anaerobic soil conditions are typical of Florida wetlands.
The procedure in evaluating a wetland is to characterize the plants within the location, whether
obligate, facultative, aquatic, etc. Then the soils are tested to determine their characteristics (dark
surface, organic accretions, oxidized rhizomes, stratified layers, anaerobic, iron, manganese,
mottles and marl). Finally, indicators of water inundation are looked for. These may include
water rings around tree trunks, algal mats, mosses, liverworts, nonvascular plants, drift lines,
plant adaptations to inundation, water flow indicators, tussocks, and hummocks.
The following is an outline of the wetlands types found in Florida. In parentheses next to
the type are synonyms for each type of wetland. The variety and the diversity of the wetland
types show the immense complexity of wetland classification in Florida.
A. Wet flatlands
1. Hydric hammock (wetland hardwood, wet hammock)
2. Marl prairie (scrub cypress, savannah, sedge flat, spikerush marsh)
3. Wet flatwoods (moist pine barren, hydric flatwoods, pocosin, cabbage
4. Wet prairie (sand marsh, savannah, coastal prairie, pitcher plant prairie)
B. Seepage wetlands
1. Baygall (seepage swamp, bayhead, bay swamp)
2. Seepage slope (herb bog, grass-sedge bog, shrub bog, seep)
C. Floodplain wetlands
1. Bottomland forest (river bottom, stream bottom, mesic hammock)
2. Floodplain forests (bottomland hardwoods, flats, oak-gum-cypress, elm-ash-
cottonwood, levee forest, river terrace, river ridge)
3. Floodplain marsh (river marsh)
4. Floodplain swamp (river swamp, seasonally flooded basins, oak-gum-cypress,
cypress-tupelo, slough oxbow, back swamp)
5. Freshwater tidal swamp (tidewater swamp, rivermouth swamp, sweetbay
7. Strand swamp (cypress strand, stringer)
8. Swale (slough, river of grass, glades)
D. Basin wetlands
1. Basin marsh (prairie, freshwater marsh)
2. Basin swamp (gum swamp, bay, bayhead swamp, swamp)
3. Bog (bog swamp, pocosin, evergreen shrub bog, wet scrub, peat islands,
4. Depression marsh (isolated wetland, flatwoods pond, St. John’s wort pond,
pineland depression, ephemeral pond, seasonal marsh)
5. Dome swam (cypress dome, cypress pond, bayhead, cypress gall, pine barrens
E. Marine and estuarine wetlands
1. Consolidated substrate (hard bottom, relic reef)
2. Unconsolidated substrate (beach, sand bar, mud flat, tidal flat)
3. Coral reef
4. Mollusk reef
5. Octacoral reef
6. Sponge bed
7. Worm reef
8. Algae bed
9. Seagrass bed
10. Tidal marsh
i. Smooth cordgrass (Spartina spp)
ii. Black needlerush (Juncus spp)
11. Oligohaline marsh
12. Salt barren
13. Tidal swamp
14. Composite substrate
Cypress swamps (strand swamps) are shallow, forested, usually elongated depressions or
channels that are dominated by bald cypress trees. They are generally situated in troughs in a flat
limestone plain. Typical plants include red maple, laurel oak, cabbage palm, strangler fig, red
bay, sweet bay, coastal plain willow, wax myrtle, buttonbush, royal primrose, poison ivy, swamp
lily, leather fern, royal fern sawgrass, swamp primrose, water hyssop, smartweed, and arum.
Canopy plants are mainly temperate, while understory and epiphytic plants are mainly tropical.
Small young trees at the outer edge of the swamp grade into large old trees in the interior, giving
a strand a distinctly rounded, cross-sectional profile. Typical animals in the swamp include
ribbon snake, cottonmouth, opossum, gray squirrel, black bear, raccoon, mink, otter, Florida
panther, and white-tailed deer.
The soils in the cypress swamp are peat and sand over limestone. The best-developed
forests are on deep peat that acts as a wick to draw moisture from groundwater up into the root
zone during droughts. The normal hydroperiod is 200 to 300 days with a maximum water depth
of about 18 to 36 inches. Water is deepest in the center where the larger trees are.
Fire occurs in cypress swamps on a cycle of about 30 to 200 years. Fire is essential for
maintenance, because without fire, the hardwood invasion and buildup of peat would convert the
strand into a bottomwood forest in a few hundred years. Cypress is very tolerant of light surface
fires, but muck fires burning into the peat can kill the trees.
Cypress trees can live for hundreds of years, have "knees" that protrude above the soil,
and lose their leaves in the winter, hence the "bald" cypress name. Bald cypress is said to be the
largest tree in North America east of the Rockies. The Florida state champion cypress, called the
Senator tree, is located in Big Tree Park near Longwood. It is the oldest cypress tree in Florida.
Cypress swamps are forested wetlands dominated by cypress trees and located along
streams and riverbanks, spring runs or in ponds with still or slow moving water. Swamps often
have long periods of flooding, and cypress is the most flood-tolerant of all the Florida tree
species. The species composition and different kinds of swamps are determined by three
environmental factors: hydroperiod, nutrient inputs, and fire. Cypress domes develop in a
depression in the ground in pine flatwoods ecosystems; the water in these ponds moves very
slowly and only drains internally through the water table
Floor of cypress wetland
There are two types of cypress trees in Florida: bald cypress and pond cypress. Bald
cypress grows in and along flowing water: river swamps, stream banks, spring runs and
lakeshores. Pond cypress is limited to ponds with still or slow-moving water. When pond cypress
is faced with soils poor in nutrients, such as the marl soils in the Everglades or the clay soils in
the Florida panhandle, growth may be extremely slow giving the trees a stunted or dwarfed
appearance. These trees are called dwarf cypress or hat-rack cypress (Brandt & Ewel 1989).
Brandt and Ewel provide an excellent summary of the differences between bald and pond
cypress: Bald cypress grows at low stem densities in locations with moderate water flow, high-
nutrient availability, and rare forest fires. Pond cypress grows at high stem densities on sites with
slow-to-stagnant water, low- nutrient availability, and occasional forest fires.
Both cypresses are known for their "knees" and buttressed trunks, but the biological
function of these is as yet undetermined. Some studies have reported that they serve to supply
oxygen to the roots of the trees and also anchor and support the tree in an unstable environment.
Others state that the knees are for storage of nutrients. The knees are a part of the root system
that grows above the soil. Knees vary in height: some are reported up to 12 feet.
The Everglades (the river of grass) is Florida’s most famous wetland. It is an enormous
expanse of grasses that occupy the southern part of the state from Lake Okeechobee to Florida
Bay. The freshwater supply comes from rain on the Kissimmee River basin and southward,
mostly in May through October. Evaporation, transpiration, and runoff consume four-fifths of
the rain, which may total 40 to 65 inches (100 to 165 cm) per year. The natural cycle of
freshwater circulation historically builds up in shallow Lake Okeechobee. It averages 12 feet (3.7
meters) deep and covers 730 square miles (1890 square kilometers). Then, the water flows south
through the glades.
The Everglades are about fifty miles (80 km) wide in places, one to three feet (0.3 to 0.9
meters) deep in the slough's center but only 6 inches (15 cm) deep elsewhere, it flowed south 100
feet (30 meters) per day across Everglades sawgrass toward mangrove estuaries of the Gulf of
Everglades’s plants and animals are adapted to alternating wet and dry seasons. During
the dry season (December to April), water levels gradually drop. Fish migrate to deeper pools.
Birds, alligators, and other predators concentrate around the pools to feed on a varied menu of
fish, amphibians, and reptiles. This abundant food source is vital to many wading birds that are
nesting during the dry season.
In May, spring thunderstorms signal the beginning of the wet season. A winter landscape
dotted with pools of water yields to a summer landscape almost completely covered with water.
Wildlife disperses throughout the park. Insects, fish, and alligators repopulate the 'glades, thus
replenishing the food chain. By December, the rains cease and the dry cycle begins again.
The Everglades are not just a “sea of grass” but also a collection of many types of
wetlands and ecosystems. Below is a brief summary of the systems associated with the glades:
Marine: Florida Bay, the largest body of water within Everglades National Park,
contains over 800 square miles (2072 square km) of marine bottom, much of which is
covered by seagrass. The seagrass shelters fish and shellfish and sustains the food chain
that supports all higher vertebrates in the bay.
Mangroves: Mangrove forests are found in the coastal channels and winding rivers
around the tip of South Florida. This estuary system is a valuable nursery for shrimp and
fish. During the dry months, wading birds congregate here to feed. Many bird species
nest in the mangrove trees.
Coastal Prairie: Located between the tidal mud flats of Florida Bay and dry land, the
coastal prairie is an arid region of salt-tolerant vegetation periodically flooded by
hurricane waves and buffeted by heavy winds.
Freshwater Marl Prairie: Bordering the deeper sloughs are large prairies with marl
sediments, a calcareous material that settles on the limestone. The marl allows slow
seepage of the water but not drainage. Though the sawgrass is not as tall and the water is
not as deep, freshwater marl prairies look a lot like freshwater sloughs.
Freshwater Slough: The slough is the deeper and faster-flowing center of a broad
marshy river. This "fast" flow moves at a leisurely pace of 100 feet (30 meters) per day.
Dotted with tree-islands called hammocks or heads, this vast landscape channels life-
giving waters from north to south. Everglades National Park contains two distinct
sloughs: Shark River Slough, the "river of grass;" and Taylor Slough, a narrow, eastern
branch of the "river."
Cypress: The cypress tree (Taxodium spp.) is a deciduous conifer that can survive in
standing water. These trees often form dense clusters called cypress domes in natural
Hardwood Hammocks: Hammocks are dense stands of hardwood trees that grow on
natural rises of only a few inches in the land. They appear as teardrop-shaped islands
shaped by the flow of water in the middle of the slough. Many tropical species such as
mahogany (Swietenia mahogoni), gumbo limbo (Bursera simaruba), and cocoplum
(Chrysobalanus icaco) grow alongside the more familiar temperate species of live oak
(Quercus virginiana), red maple (Acer rubum), and hackberry (Celtis laevigata).
One of the dominant emergent ecosystems along the coast of Florida is the mangrove.
Mangroves are flowering plants, growing in dense populations along the shoreline in narrow bands,
perhaps reaching their maximum growth in brackish water (up to 10 meters in height). The three
principal species of mangroves in Florida are:
1. Rhizophora mangle - the Red Mangroves are characterized by prop roots, may reach 25 m
in height, their propagules are pencil shaped, they flower generally in summer and spring
but can flower throughout the year, and possess a small reserve of leaf buds. The red
mangrove can exclude salt.
2. Avicennia germinans - the Black Mangroves are characterized by pneumatophores (2-20
cm above the soil), can reach a height of 20 m, their propagules are lima-bean shaped,
and they flower in spring and summer. The black mangrove can excrete salt.
3. Laguncularia racemosa - the White Mangroves are trees that grow to 15 m, their
propagules are small diamond shaped, and they flower in spring and early summer. The
white mangrove can also excrete salt.
4. Conocarpus erectus- Buttonwood is a mangrove associate, usually growing further inland
from the other three mangroves. It is a tree that grows up to 14 m, not viviparous.
Davis in 1940 stated the importance of mangroves in shoreline stability: they are not only
important in extending coasts and building islands, but also in protecting coasts from excessive
erosion caused by tropical storms and hurricanes. Mangroves act as sediment traps and water filters.
As tides move water back and forth over the roots of the mangroves, particulates from the water
column are trapped between the roots. Over time, the sediments may accumulate to the extent of
forming islands and barriers along the coastline, each one acting as a large water filter. Removal of
mangroves results in the loss of water clarity in the bay. Lewis in 1979 calculated that 44% of
original tidal mangroves in Tampa Bay have been lost to development and other causes during the
In addition to the above benefits mangroves provide the following: habitat for a wide variety
of animals (over 220 species); nursery areas for sport and commercial fishes and invertebrates; and,
they have aesthetic appeal. Therefore, loss of mangroves would affect an entire ecosystem and not
just a few species.
There are two other emergent plants that are of importance to the quality of water in the bay:
Spartina alterniflora (smooth cordgrass) and Juncus roemerianus (black needlerush). These plants
usually grow along the bottom slopes in front of the mangroves and act as sediment filters and
shoreline stabilizers, much like the mangroves. Their populations have also declined significantly
during the past century.
The term Mangrove is from a Portuguese word for tree (mangue) and an English word for
a stand of trees (grove), therefore the term Mangrove describes a type of tree growing in
estuarine environments. A Mangrove community consists of plants growing in estuarine
environments, synonyms include: tidal forest, tidal swamp, mangrove community, mangrove
ecosystem, mangal and mangrove swamps
Red Mangrove “mangle”
Some of the characteristics of mangroves are:
Morphological specialization to the coastal environment, such as aerial roots and
Mangroves possess a physiological mechanism for salt exclusion and often the ability
to excrete salt
Taxonomic isolation from terrestrial relatives.
Worldwide there are 34 species (9 genera - 5 families) that comprise major elements
and 27 species (11 genera and 11 families) that comprise the minor elements of
90% of the mangroves in Florida are located in Dade, Collier, Lee and Monroe
Counties. Northern limits are Ponce de Leon Inlet on Atlantic Coast and Cedar Key
on the Gulf of Mexico.
Mangroves do not occur where annual temp is below 19o C (66oF), as climatic stress
increases plant stature decreases, hurricane prone areas also have reduced stature
Mangroves are facultative halophytes, but are usually out-competed in freshwater
Mangroves are tropical species that do not develop well where the average temperature is
less than 66 F (l9 C). High temperatures above l07 F (42 C) are also thought to be limiting.
Normally, temperature fluctuations greater than 50 F (l0 C) are not tolerated well. In Florida, the
impact of low temperatures on mangroves results in decreases in structural complexity of the
community. Often during winter freezes mangroves die of, only to re-grow in the following
years. When compared to mangrove communities of areas with more favorable temperature,
Florida’s mangrove communities show decreased tree height, decreased leaf area, and increased
All three species trap, hold, and stabilize intertidal sediments. With these facts in mind,
early hypotheses are misconceptions that mangroves are “land builders”. The role in land
building is more passive than active by sediment trapping and litter production. Probably, a
better term for mangrove is a “land stabilizer”. Black mangroves may be the best land stabilizer
due to easier seedling transport, quick aerial root production, underground root systems increase
sediment holding capabilities, higher tolerance to cold temperatures, better ability to inhabit
"artificial" sites (dredge, fill, etc.). Red mangroves are second best and whites are the worst.
During extreme storms and hurricanes mangrove forests protect landward coastal area by
mitigating damage from waves, currents, and winds.
Red Mangrove Propagules
A variety of organisms utilize mangrove habitats. A myriad of marine species is found as
inhabitants of the underwater prop root complex and tidal channels. All fish and shellfish caught
commercially, and by recreational means utilize mangrove habitat at some point in their life
cycle. In addition to the marine organisms, both terrestrial organisms and birds utilize the forest
floor, root complex and the canopy. Florida mangrove communities are also known to provide
habitat for a number of threatened and endangered species. Among the endangered species are
the American Crocodile, Hawksbill and Atlantic Ridley Turtles, Bald Eagle, American Peregrine
Falcon, Key Deer, Barbados Yellow Warbler, Atlantic Saltmarsh Snake.
Acreage estimates of 430,000-540,000 acres (l981) of mangrove communities vary
widely due to inadequate ground truthing. Ninety percent of these communities are in Lee,
Collier, Dade, and Monroe counties of south Florida. Approximately 280,000 of these acres are
held by Federal, State, County governments, or non-profit organizations. The majority of these
acres are within the Everglades National Park. The rest account for the undeveloped shoreline of
the counties listed above.
Due to increased water turbidity in mangrove waters, roots are extremely susceptible to
clogging, as well as prolonged flooding and damage due to boring organisms. Other natural
deleterious effects resulting from organisms are gall production by wasps and parasitic yellow
lichens. Extreme hurricanes extensively damage mangrove forests.
Natural destruction is relatively low compared to human impact of these communities. A
variety of deleterious stresses include dredging, filling and dike building; oil spills; herbicide and
human waste runoff. Estimates of a 5% loss of acreage have been given for loss this century.
However, an estimate in certain locales of wetland loss is up to 44%. However, urban destruction
usually results in a total loss of habitat. As population growth continues, the pressures to alter
these communities continue.
For mangroves the quality, location and quantity of water are essential to primary
production. Epiphytes attached to the roots can add significantly to this production. Estuarine
mangrove systems are second only to the tropics in primary productivity. Estimates of 8.8 dry
tons/hectare/year of organic material have been recorded. Factors affecting productivity are
species composition, age, competition, substrate, wave action, bird activity, hurricanes, etc.
There are three methods that produce estimates of primary productivity: biomass, gas exchange,
and litter fall. Another method of estimating production is net amount of carbon. In general, Red
mangroves have the greatest net production, Blacks intermediate, and Whites the lowest figures
of net primary production.
Red mangroves intercept 95% of the available light at 13 feet (4 m) below top of the
canopy. Therefore, it is not surprising that 90% of the leaf biomass exists in this upper portion of
the canopy. Possible explanations are shading and environmental stress (salt, anaerobic
conditions, etc). Litter fall of Florida mangrove forests estimates range from 2-3 dry g/m2/day in
well-developed stands. Leaves fall all year with a minor peak in early summers. Additionally,
sporadic litter fall exists after stress.
Detritus, enriched nutritionally by its microbial population is utilized as a food source by
a variety of organisms. The role of mangrove detritus and its importance to nearby reef systems
is problematic. Surface waters associated with mangrove habitats are often characterized by a
wide range of salinity (0-->40ppt), low macronutrient concentrations (especially Phosphorus),
and a relative low dissolved oxygen concentration. These conditions are most pronounced in the
Everglades with decreased pronounced effects in the Keys
The general (less specific) classification of forests in Florida has the following types:
pine flatwoods, scrub, and hardwood forests. Each of these forests has their own ecological
background, unique species, and distinctive ecological contributions to Florida’s overall
Pine flatwoods are dominated by longleaf pines, slash pines, and saw palmettos. Pine
flatwoods usually contain 50 to 75 species of plants per acre. Cypress swamps and hardwood
hammocks often disrupt them. Pine forests occupy about 50% of Florida's land area. The
majority of Florida's wildlife that lives in swamps and hammocks also use flatwoods at least part
of the year. Summer rains often temporarily flood Flatwoods. Lightning normally starts fires
every few years during the spring and summer season with the fires quickly burning through the
forest. After the fire the ash fertilizes new growth. Pines are spared because of their thick bark;
shrubs and herbs re-sprout from their roots. Pine flatwoods along the lower East Coast grow on
rough limestone called rocklands. Very little of this habitat is left because most has been cleared
and crushed for farming or house lots except in a few parks and in Everglades National Park.
The pine forest has a low flat topography, relatively poorly drained, acidic sandy soils,
sometimes underlain by organic matter. They occupy old, flat shallow marine deposits. It is the
most extensive community in south Florida except for freshwater marsh, i.e. the Everglades.
The dominant species in Florida is the slash pine (Pinus elliottii var. densa). Its canopy
may reach 30 meters but often stunted because of underlying hardpan. The density of the trees
varies considerably from tens of trees to 5,000+ per hectare. The typical fire cycle is a 2-year
burn cycle with fire frequency about once every 4 to 7 years.
The endemic species of a pine flatwoods are:
Nemastylis floridana (ixia)
Panicum abscissum Cutthroat grass
Polygala rugelii Yellow bachelor's button
Sabal etonia Scrub palmetto
The typical exotics in a pine forest are:
Melaleuca quinquenervia Melaleuca
Schinus terebinthifolius Brazilian pepper
The term “scrub” refers to any scraggly or stunted trees or bushes growing thickly
together. Land covered with such growth, like palmettos is called a scrub.
Florida Scrub is open pineland having oaks (Quercus spp.) and palmettos (Serenoa
repens) growing beneath. Florida scrub vegetation includes several distinctive vegetation types.
These include sand pine scrub, rosemary scrub, oak-saw palmetto scrub, coastal scrub and
scrubby flatwoods. South of Lake Okeechobee the scrub pine (Pinus clausa) is the only short-
needled pine. Scrub pine is readily distinguished from the other pines south of Lake Okeechobee
by the short needles (4-8 cm.), small cones (5-6 cm. long), and dark green color of the trees. The
light green, long needles (15-30 cm.), and large cones (6-10 cm. long) of the other common pine,
the slash pine (Pinus elliottii), makes it easy to recognize. Over most of the area south of the
Lake, these are the only two pines. A third species, the long-leaf pine (Pinus palustris), common
north of Lake Okeechobee has been reported south to Lee and Martin Counties. Cones and
leaves of the long-leaf are even larger than the slash pine.
Growing below the scrub pines are three common oaks. Oak species are notoriously
difficult to recognize but usually these three are distinctive. The sand live oak is the easiest to
identify since it has oblong leaves that curl under at the margins (revolute), and are densely
white-pubescent below. Many consider this a variety of the live oak and call it Quercus
virginiana var. geminata. Others prefer to call it a distinct species, Quercus geminata. The other
two are the scrub oak (Quercus chapmanii) and the myrtle oak (Quercus myrtifolia). These are
occasionally difficult to separate but the scrub oak has at least some leaves with tooth-like lobes
on their margins ending in a bristle. The myrtle oak usually has entire leaves with no bristles.
Many areas of ground are bare of plants while others have clusters of various species.
Often the shrubby rosemary (Ceratiola ericoides) is in the community. Rosemary, not to be
confused with the cooking spice, is a pioneer. As the site matures, the oaks and palmettos begin
to squeeze rosemary out. Only when there is a disturbance, from a falling tree, a road, a fire, or
something similar, do the rosemary seedlings appear.
The ground layer is often bare except for pine needles and cones, or it may be covered
with lichens. The lichens are of the deer moss or reindeer moss type. Often about a dozen species
are present on any single site, many belonging to the genus Cladonia. Kurz (1942) listed twelve
lichens in several genera, but many of them grow only on trees. One of the more obvious tree
lichens is the old man's beard. This lichen looks to some people like the pineapple relative
Spanish moss. (From: Austin, D. F. 1998. Florida Scrub.)
Scrub is found on the slightly higher lands near the high pine habitat. As such, it is
another of Florida's fire dependent communities. The soil is exceedingly nutrient poor in these
highly drained ecosystems. Consequently, most plants grow very slow and are stunted from lack
of nutrients. It is also not unusual to see open patches of sandy soil in the scrub habitat.
The land historically occupied by scrub habitats is also some of Florida's higher, and
most sought after land for development. Much of the scrub habitat is now gone, replaced by
housing developments and citrus groves. Well preserved examples of the scrub habitat are
limited to parts of the Ocala National Forest, the Lake Whales Ridge, along Atlantic coast from
Cape Canaveral to West Palm Beach and along the panhandle coast from Ft. Walton Beach to
Scrub is probably the oldest plant community in Florida. According to data taken from
pollen profiles in lake and pond sediments, a community much like Scrub was in central Florida
about 5,000 years ago. Some think that the community was formed during the Pleistocene.
Particularly convincing data for a Pleistocene age is given by the distribution of Scrub on sand
ridges that appear to be coastal dunes. These dunes were apparently deposited during the
Pleistocene glaciation sea-level changes. No one has determined exactly how these ridges were
formed; some suggest beach ridge origin such as those now east of the Intracoastal Canal; others
believe in saltation (wind-blown) deposition. In Palm Beach County there are six or seven
remnants at different distances from the ocean; all are in different stages of erosion.
In “Ecosystems of Florida” by Myers and Ewel, a chart is presented that compares the
scrub ecosystem with the high pineland, a similar ecosystem but not covered in the text. The
following chart is adapted from the book:
The hardwood forests of Florida, often referred to as hammocks, occur in narrow bands
of vegetation scattered throughout middle to northern Florida. The hardwood forests contain a
diverse assemblage of trees. Geologists believe their origin dates back some 110-120 thousand
years ago, when receding ancient seas exposed coral reefs. Deprived of its life-giving seawater,
the living coral soon died, leaving slowly fossilizing limestone behind to support some of
Florida's - even North America's - rarest plant and animal communities.
Hardwood forests are often dominated by large oaks, the most impressive of which are
the southern live oaks, usually draped with Spanish moss and other air plants. Hardwood forests
dominated by evergreen, broad-leaved trees are called hammocks, a name that means shady
place. Sabal or Cabbage palm grows abundantly in many hammocks.
In North Florida, hardwood forests and hammocks have an extraordinarily diverse flora--
more species of trees and shrubs than any other plant community in the continental United
States. The hammocks of South Florida and the Keys, growing on a rocky limestone soil, are
especially interesting because they contain tropical hardwood trees and wildlife common in the
Bahamas and other tropical locales
The tropical hardwood hammock is a self-maintaining community that usually remains
untouched by fire or flood. These tiny "islands" support over 20 species of broad-leafed trees,
shrubs, and vines, most of which are native to the West Indies. Subject to thin soils and relatively
low rainfall in a tropical climate, tropical hardwood hammocks form a low canopy beneath
which is a dense, sometimes impenetrable tangle of shrubs and vines. Hidden in the hammocks
are some of Florida's most rare and most beautiful animal life. Historically, tropical hammocks
were found as far north as Cape Canaveral on the Atlantic coast and to the mouth of the Manatee
River on the Gulf coast. These more northerly hammocks had unique characteristics all their
own. Today, most of the northern hammocks have been destroyed, leaving only remnant stands
in south Florida, mostly in the Florida Keys.
The dominant species in this habitat classification varies depending on its location in the
state. Hammocks located in the panhandle are dominated by several species of oaks, hickories,
and magnolias. There is a diverse understory and a number of plants that are found only in this
part of the state.
In the north central part of Florida, the hammocks begin to transition from ones
dominated by temperate species to one with a tropical influence. Oaks species are dominate with
cabbage palms becoming more abundant the further south you look. The oaks of this region tend
to be evergreen species.
The coastal hammocks of the southern part of the state contain the highest percentage of tropical
hardwoods. Evergreen oaks grow with gumbo-limbo, mastic, strangler figs, and a variety of
tropical understory plants.