Download Untitled - Odyssey Earth

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The River of Grass
Geology
The Everglades are a vast and shallow wetland unlike any other in the world. To understand them we
can imagine a flat table of limestone rock tilted ever so slightly towards the sea, dropping in elevation
less than 2 inches for every mile. Water running off this table of limestone flows like a sheet…so slowly
you can’t see it move. This is described as sheet flow. In 1947 Marjory Stoneman Douglas captured this
idea when she coined the term “river of grass.”
The floor of the Everglades is a recent limestone
formation deposited during the Ice Ages when
South Florida was periodically covered by the sea.
Water from the Everglades fills the porous rock
and flows through it and over it. People in South
Florida receive most of their water from this layer
of rock by drilling into it to create wells. This
limestone slab is known as the Biscayne Aquifer.
The surface of the Biscayne Aquifer has only slight
relief. For the most part the wet prairie has no
more than a thin skin of soil in which a stiffbladed sedge called sawgrass grows. In most
places the water is knee deep or less. But the
oolite limestone is also pocked with deeper
solution holes. These ponds may be rimmed with
cypress trees or willow trees.
How the System Works
The Everglades receive most of their waters from
the north. Rain falling on the Kissimmee Prairie in
Central Florida becomes part of the Kissimmee River and then flows to Lake Okeechobee. Historically,
during the rainy season, the lake would overflow, spilling its contents over the southern rim. At this
point the water would drift south into the Everglades. Eventually the water makes its way to the coast.
Here the fresh water mixes with salt water from the bay. This area is dominated by mangrove trees,
and the brackish environment forms an important estuary where saltwater fish and shrimp can raise
their young. The young feed, in part, on microorganisms that flow in with the Everglades waters.
Food for thought:
When the Everglades were in their healthy, natural state….before hundreds of miles of canals
were cut through the landscape….there was plenty of water to cover the environment, even
during much of the dry season. Discuss how the shrinking water affects the plants and animals
of the Everglades as they compete for limited space and resources.
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Everglades Habitats
Here are a few of the important habitats that make up the Everglades ecosystem:
Sawgrass prairie - a large expanse of sawgrass, found mostly in shallow Everglades waters about
knee deep or less. Sawgrass is actually a type of sedge, not a true grass. Sawgrass is an important
primary producer of the Everglades food web.
Slough - a low-lying area that channels water through the Everglades. These marshy rivers are
relatively deep and rarely dry out completely. Sloughs bring life-giving waters from Lake Okeechobee
southward. Everglades National Park contains two major sloughs: the Shark River Slough and the
smaller Taylor Slough.
Cypress dome - the cypress dome gets its name from its dome-like shape which often looks like
an island amid the sawgrass prairie. Cypress domes are found in water that is somewhat deeper than
surrounding prairie and marsh-land. Cypress trees often grow in a ring surrounding an even deeper
“gator hole,” which is excavated by resident alligators. Gator holes often retain a bit of water during
the dry season, helping alligators and other organisms to survive the winter dry months.
Hardwood hammock - a dense forest of broad-leafed trees that grows on a natural rise of only a
few inches in elevation. The seasonal flow of water in areas of lower elevation around the hammock
islands helps give these hammocks a distinct teardrop shape. Many tropical tree species such as
mahogany, gumbo limbo, and cocoplum are found here. The diversity of plant life supports an equally
diverse array of animal life.
Pine rocklands - as with hardwood hammocks, these forests often take root in areas of slightly
higher elevation, often where fire has occurred. The rugged ground is canopied mostly by slash pine,
but the understory supports an amazingly diverse assemblage of plant-life and provides homes and
nesting grounds for many birds such as the pileated woodpecker and the swallow-tailed kite.
Food for thought:
Discuss how the wide variety of specialized habitats in the Everglades helps to promote
biodiversity.
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The Dry Season - A Struggle for Survival
South Florida really only has two seasons instead of four. These seasons are the wet season (May October) and the dry season (November – April). Starting in October the heavy summer rains taper off.
For a time the river of grass seems unchanged, but by January the prairies are starting to dry up. Many
small, aquatic organisms become stranded or are gobbled up by raccoons, otters and wading birds.
Soon the only water left is in scattered ponds which now become crucially important for aquatic
turtles, gar, bass, water snakes, otters, alligators and anhingas. From December through April survival
is a pond existence. When the rains come again in April or May, what’s left of the ponds becomes the
breeding stock for the next generation of Everglades life.
Everglades Food Webs
Producers
Primary producers, or autotrophs, are organisms that harness the radiant energy of the sun to produce
bio-mass from inorganic compounds. This is achieved through the process of photosynthesis.
Producers are mostly (but not exclusively) green plants.
Sawgrass and periphyton are two of the most important primary producers in the Everglades.
Sawgrass - a type of sedge which grows in shallow Everglades waters, can grow up to 9 feet tall and is
edged with sharp saw-like teeth. Some organisms, such as deer, munch on the softer base and many
species of birds feast on its seeds. Sawgrass marshes provide breeding habitat for birds, amphibians
and other creatures.
Periphyton - a complex mat of algae and microorganisms. Periphyton covers much of the floor of the
Everglades and coats many of the submerged plants. It provides food for billions of tadpoles, small fish
and aquatic insects.
Primary consumers
Primary consumers (herbivores) are organisms that rely on producers (autotrophs) for food. The
Everglades are incredibly bio-diverse, but here are a few examples:
Mosquito larva - in its second phase of metamorphosis the mosquito is an aquatic larva that swims
around and feeds on organic matter. The mosquito larva loves periphyton.
Sailfin molly - these small fish feed mostly on organic matter, especially algae such as periphyton.
White-tailed deer - the deer is one of the larger mammals found in the Everglades, but it is a
herbivore (plant eater) that feeds on shoots, leaves, grasses, and the tender bases of sawgrass.
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Secondary consumers
Secondary consumers are animals that feed mostly on primary consumers.
Wading birds - this is a broad category of birds that includes the herons and the egrets, as well as
birds like the wood stork, the roseate spoonbill and the white ibis. Wading birds are usually found
foraging in shallow waters and marsh areas and feed mostly on small fish, insects, small snakes and
aquatic invertebrates.
Frogs - there are many species of frogs in the Everglades including the pig frog, the leopard frog and
the green tree frog. Frogs are amphibians. Most frogs are also carnivorous and will eat just about
anything they can fit into their mouths including insects, crayfish…even other frogs!
Florida gar - these long, toothy fish eat a variety of smaller animals including shrimp, crayfish and
other fish.
Cottonmouth - also known as the “water moccasin,” it is the world’s only semi-aquatic viper. Like
other pit vipers, the cottonmouth packs a hemotoxic venom which helps to subdue its prey of fish,
amphibians, birds, small mammals and even baby alligators.
Apex Predator:
The American Alligator
The American Alligator is one of the world’s two true alligators, the Chinese alligator being the second.
Along with the American crocodile, it is one of only two crocodilian species found in South Florida,
preferring the fresh water habitats of the Everglades while the crocodile is found mainly in salty or
brackish waters of the coast.
The American alligator is an opportunistic predator that will eat just about any animal it can catch,
including fish, birds, snakes, mammals, amphibians and turtles. It will eat road kill. Large gators have
even been known to resort to cannibalism.
The American alligator has one of the strongest bite-forces in the animal kingdom…strong enough to
crack a turtle shell. Its conical teeth are designed for grabbing and holding prey rather than chewing or
cutting. The alligator uses a technique called the “death roll” to dismember large prey into pieces small
enough to swallow.
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Food for thought:
Some organisms are very picky about what they consume, but many organisms will consume a
large variety of food sources. When we talk about the transfer of energy from producer all the
way up to apex predator, we usually compare the process to a network or “web.” Choose from
the list below and fill in the blanks on the diagram to create a basic Everglades food web. Draw
arrows between the circles to show the transfer of food energy from one organism to the next.
sawgrass, periphyton, mosquito larva, sailfin molly, white-tailed deer,
Florida gar, cottonmouth, American alligator
wading bird, frog,
Alligator reproduction
Alligators mate in the spring. This is a time when males become aggressive with each other in their
competition for mates. Sometimes they raise their heads and slap their jaws on the water as a
ritualized way of demonstrating their power. Fights break out and severe wounds or even death can
result.
In the spring both male and female alligators bellow. The bellowing of the male is slower and lower
pitched. The sound travels over half a mile and can help potential mates find each other. Alligators
bellow both day and night. After mating, males play no further role in reproduction.
An average of 30-40 eggs are laid by the female alligator in late June or early July. A few days before
this she gathers a large mound of vegetation: cattails, sawgrass or whatever is available. If the female
builds the nest in the water, she builds it high enough to keep the eggs dry. Heat from the rotting
nesting material helps to incubate the eggs.
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Alligator eggs incubate for an average of 59 days. Eggs in the warmest part of the nest which reach
temperatures over 91 degrees Fahrenheit will produce male embryos. Those below 85 degrees will
become females. When the eggs begin hatching, the mother hears the cries of her hatchlings. She
usually waits until night and then begins digging them out. The mother assists her young by carrying
them down to the water in her mouth and may even hasten the hatching of eggs by rolling them
around in her mouth.
Alligator hatchlings do not feed for at least a week because each baby has a bulging yolk sac that must
first be absorbed. When they do become hungry, the young will have to catch their own food.
Although the mother does not feed her young, she does protect them until at least the following
spring.
The Everglades in Peril
In the early 1900’s man began to change this delicate system. It started with a series of canals and
levees that were built to provide flood control and to drain the land immediately south of Lake
Okeechobee for agriculture. Much of the water that would have flowed naturally from the lake to the
Everglades was directed instead to the coastal areas.
The canal system eventually spread like a web, and the
Everglades began to go dry. In the winter, the effects
were disastrous. Many of the shallow ponds that would
have held water dried up completely. This loss of fish
and other aquatic species reduced the population of
alligators, wading birds and other predators as well.
To make matters worse, the waters flowing south to the
Everglades were no longer pure; they were loaded with
dissolved fertilizers being applied to the vegetable and
sugar cane fields near Lake Okeechobee. Even the water
reaching the lake from the Kissimmee Prairie was over
enriched by fertilizer from cattle ranches. This was partly
due to an epic miscalculation. In 1961 the U.S. Army Corps of Engineers began straightening the
Kissimmee River in an effort to deliver more water to Lake Okeechobee. But by taking the meanders
out of the Kissimmee and bypassing its surrounding marshes, the river lost its ability to cleanse the
polluted water. Today algae blooms threaten to kill Lake Okeechobee biologically (when algae die,
bacteria feed on them and multiply, depleting the oxygen in the water). The enriched water also
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causes nutrient-loving cattails to choke out the native sawgrass. Today the Kissimmee is being restored
by putting the meanders back.
Although Everglades National Park covers about 1.5 million acres and is the second largest national
park in the lower 48 states, it represents only a fraction of what used to be called the Everglades. What
was once an incredibly productive ecosystem is now the most endangered national park in the United
States. To reclaim the Everglades, ways must be found to restore its water flow, both in quality and
quantity.
Comprehensive Everglades Restoration Plan (CERP)
Over 100 years ago man’s heavy machinery began a gradual devastating drainage of the Everglades.
Now, after many years of research, public debate and action by our lawmakers, a plan for fixing up the
Everglades has been created.
CERP (Comprehensive Everglades Restoration Plan) was signed into law by president Clinton, Dec. 11,
2000. Considered the largest ecosystem restoration program ever attempted, The original estimate
determined that the Implementation Plan will cost over $7.8 billion, with an additional cost of $182
million annually to cover operation and monitoring. Half of this total cost will be paid by the federal
government and half by the state of Florida. The entire plan is estimated to take at least 30 years to
complete.
Goals include:
A. Improve Sheet flow of water to the Everglades.
B. Improve quality of water coming into the Everglades.
C. Provide flood control.
D. Provide water to cities.
E. Provide water for agriculture.
F. Adaptive Management- adapt the plan according to research.
Projects include:
1. Eliminate some canals and levees.
2. Dig a few new canals to improve direction of water flow.
3. Raise part of Tamiami Trail to allow water from Water Conservation Area 3 to flow
more freely to the Everglades National Park.
4. Create more water storage capacity by creating new reservoirs.
5. Create Stormwater Treatment Areas (STA’s).
Food for thought:
Humans are a part of the environment, just as sawgrass, fish and alligators are part of their
environment. Talk about some of the ways we have affected the areas in which we live. What
are some of the ways we have hurt the ecosystem? What are a few things we can do to improve
the health of the ecosystem? How does the health of the Everglades affect our own lives?
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Vocabulary words
sheet flow - an overland flow or downslope movement of water taking the form of a thin, continuous
film over relatively smooth surfaces and not concentrated into channels
limestone - a sedimentary rock composed largely of calcium carbonate (CaCO3). Many limestones are
composed of skeletal fragments of marine organisms such as coral.
mangrove - a category of trees, not all closely related, that are highly tolerant of salty environments. In
Florida we have 4 species of mangrove trees: the red mangrove, the black mangrove, the white
mangrove and the buttonwood.
brackish water - a mixture of salt water from the sea and fresh water from the land.
estuary - a transition zone between river environments and ocean. Estuaries are subject to both
marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as
flows of fresh water and sediment.
autotroph - a "producer." An organism that produces complex organic compounds (such as
carbohydrates, fats, and proteins) from simple inorganic substances present in its surroundings,
generally using energy from light (by photosynthesis).
photosynthesis - a process used by plants and other organisms to convert the light energy captured
from the sun into chemical energy that can be used to fuel the organism's activities.
herbivore - an animal that eats plants.
incubate - to maintain eggs, organisms, or living tissue at optimal temperature for growth and
development. Birds often incubate their eggs by sitting on them to provide warmth. Alligators create
nests of decaying plant matter to keep their eggs warm.
embryo - any multicellular plant or animal in a developmental stage preceding birth or hatching.
hatchling - the newborn of animals that develop and emerge from within hard-shell eggs.
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Useful Web Sites
For Everglades National Park: www.nps.gov/ever
For information about Everglades Restoration: www.evergladesplan.org
For information on how to get involved: www.evergladesfoundation.org
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Quiz answers:
1. T 2. T 3. F 4. F 5. T 6. F
7. water/ any of the following: pollution, nutrients, fertilizer, nitrogen, phosphorus
8. sawgrass
9. restoration
10. periphyton
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Surviving the Everglades
quiz
1. The Everglades can be considered a shallow and very wide river.
True
False
2. The temperature of alligator eggs during their development determines whether they
develop into males or females.
True
False
3. Winter is the rainy season in the Everglades.
True
False
4. In the Everglades, hardwood hammocks grow in low places in the limestone rock
where it stays wet all year long.
True
False
5. The mother alligator does not provide food for her young, although she does protect
them.
True
False
6. The digging of a vast canal system in southern Florida has provided more water for
the Everglades.
True
False
7. The Everglades habitat suffers from not enough__________________ and too much
__________________.
8. The sharp-edged plant (a type of sedge) that covers so much of the Everglades is called
__________________.
9. CERP stands for Comprehensive Everglades __________________ Plan.
10. Both the mosquito larva and the sailfin molly feed on __________________.
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