The Florida peninsula is bordered by 1900 km (1181 miles)
of tidal coastline, second only to Alaska. Of this total, approximately 1200 km
(746 miles), primarily along Florida’s east coast, consists of sandy beaches
where high energy waves constantly break along the shoreline. In northern areas
along the east coast of Florida, including the northern Indian River Lagoon
area, sands are composed principally of quartz that originated in the
Appalachian Mountains, and calcium carbonate from rock and shell deposits.
Further south, the amount of quartz in sand decreases steadily, and sand
composition becomes primarily calcium carbonate.
Beaches lie at the interface between the land and the
ocean. East coast beaches in Florida, especially those in the Indian River
Lagoon area, are generally dynamic, high-energy, areas. The unique topography
and slope of any beach area is the result of interactions between both abiotic
and biotic factors. Key physical processes in beach and dune formation are wave
action, erosion, sand accretion by winds, overwash, and the deposition of salt
spray (Stalter 1976; Tyndall 1985). Important biotic factors generally center
around the ability of plants to colonize and grow while withstanding the adverse
effects of being buried in sand and inundated by sea water. Additionally,
colonizing species of plants must also be able to tolerate the xeric conditions which result from sand being generally well drained
with low nutrient availability.
The slope of a beach and the shape of its dunes are
heavily influenced by tides, wind patterns, storm events and the movement of
sand that often accompanies these events. Sand is typically deposited on beaches
as waves break on the shoreline and their energy dissipates. Whatever
particulates that had been suspended in the wave are deposited on the beach and
then dragged down the face of the beach again in the wave’s backwash. Since
the energy of backwash tends to be far less than the initial energy of the wave,
there is typically a net onshore transport of sand. However, hurricanes and
their accompanying storm surges often have the effect of either eroding sands
offshore, or overwashing and destabilizing dune systems, redepositing sands
inland.
Wave action tends to shape the beach slope as well,
with high-energy waves tending to increase the steepness of the slope, and
lower-energy waves resulting in flatter beach profiles. On high-energy beaches
in the IRL region, beach profiles change seasonally. In summer, waves tend to
occur as swells that move sediments up the beach, building berms and providing
sands for dunes. However, during fall and winter, the steep waves that accompany
storms erode beaches and flatten out the beach profile, depositing eroded sands
seaward on longshore bars (Bearman {ed.} 1989).
Beach Plants:
Due to sometimes intense wave action, strong winds, and the presence of sea
water, most plants are unable to successfully colonize beach areas directly
along the shoreline. However, several species are able to become established in
the upper beach zone, thus enabling sand stabilization and subsequent
development of dune systems. Plants occurring on beaches and dunes tend to
occupy specific regions according to their individual growth patterns and
environmental tolerances. Most beach plants occupy the area closest to the
shoreline in the pioneering zone, which extends landward from the wrack line on the upper beach through the dune area. Pioneering species must be
highly specialized to tolerate the severe environmental challenges they face.
The most successful pioneering species in coastal zones are halophytic, meaning
that they are able to thrive under highly saline conditions. Many of these same
plants also have high growth rates, with some plants actually stimulated to grow
faster as they become buried in sand.
Most pioneering species are also able to withstand
xeric conditions, low nutrient availability, heavy winds,
inundation by sea water, high soil temperatures, and burial in sand. Pioneering
species are generally vine-like or succulent, having waxy or hairy coverings on
their stems and leaves. They produce many seeds that are widely disbursed,
helping them to become quickly established or recolonized on beach areas.
Pioneering species also tend to spread rapidly as they grow, creating a network
of creeping stems so if one part of the plant is uprooted or buried in shifting
sand, other portions can continue to grow. Their roots also help to anchor sand,
and thus assist in subsequent dune building and stabilization.
Beyond the pioneering zone, in the shelter of swales
and secondary dunes, plants are generally more protected from the effects of
salt spray, seawater and sand burial, and the resulting communities can be much
more diverse. When dunes become established and remain stable over time, plants
continue to grow and reproduce, eventually enriching the sandy soil with humus
from leaf litter and decaying plants. As humus accumulates, soils become richer
and hold more water. This allows other types of vegetation to take root, and
begins the process of succession whereby vine-like or herbaceous pioneering
species are eventually replaced by shrubs and trees.
Key species of plants that colonize the upper beach
zone include salt-tolerant pioneering species such as shoreline sea purslane (Sesuvium
portulacastrum), seashore dropseed (Sporobolus virginicus), beach peanut
(Okenia hypogaea), railroad vine (Ipomoea pes-caprae), West Indian
sedge (Remirea maritima) and knotgrass (Paspalum distichum).
Beach Animals:
At first glance, beaches may appear to support comparatively few animal
species; however, beaches are complex habitats that support many species of
animals unique to shorelines, many of them too small to notice. Successful
animal inhabitants of beaches include the often overlooked but highly abundant
meiofauna that live
between sand grains, and the more familiar species of annelid worms that
burrow into the substratum. Various bivalve and snail species, as well as many
species of small crustaceans such as isopods and amphipods inhabit the wrack
line along the shore. Surf clams and mole crabs are 2 species that stand out as
inhabitants of the surf zone. Both of these animals are extremely fast
burrowers, able to rebury themselves almost as fast as they become exposed in
shifting sands. The surf clam, also known as the variable coquina (Donax
variabilis), is a filter feeder that uses its gills to filter microalgae,
tiny zooplankton, and small particulates out of seawater. The mole crab (Emerita
talpoida) is a suspension feeder that feeds by capturing zooplankton with
its antennae. Further up the beach, somewhat removed from intense wave action,
is where the ghost crab (Ocypode quadrata) makes its home by burrowing into the
sand.
Although many species of birds are often observed on
beaches, only 5 species of shorebirds: 1) the snowy plover (Charadrius
alexandrinus), 2) the black skimmer (Rynchops niger), 3) the least
tern (Sterna antillarum), 4) the royal tern (Sterna maxima), and
5) the sandwich tern (Sterna sandvicensis) prefer nesting sites on bare
sands in the upper beach zone. Snowy plovers, however, are known to nest only
along the Gulf coast of Florida.
Additionally, of the 7 species of sea turtles, 6 are
dependent on Florida beaches for nesting during the summer. In fact, the Florida
coastline is the most important nesting area for sea turtles in the western
Atlantic, though sites in Natal, South Africa, and the islands of the Red Sea
are also utilized (Johnson and Barbour 1990). In Florida, loggerhead turtles and
green turtles are by far the most commonly observed, with loggerheads laying an
average of 3000-4000 nests per year on Florida beaches, and green turtles laying
approximately 300 nests per year. Highest sea turtle nest densities are observed
in southern Brevard County, from south of Cape Canaveral to Sebastian Inlet,
though sea turtles nest even along the highly developed beaches of Broward and
Dade counties. In human-impacted areas, it is often necessary to dig up turtle
nests and rebury the eggs in other areas to insure successful hatching.
Many species utilize beaches as feeding areas.
Sandpipers and other shorebirds, wading birds, and even some fish such as the
Florida pompano employ the surf zone to prey on animals that either wash out of
the sand due to wave action, or come close enough to the shore to be captured.
Some mammals are also known to utilize beaches as feeding grounds. Among these
are raccoons, feral cats and foxes, which are known to patrol the wrack line at
the high water mark and scavenge eggs from sea turtle nests (Myers and Ewel,
1990).
Human Impacts:
Florida’s barrier islands have been extensively developed and support a
large human population, leaving little of the original landscape unaltered.
Florida’s beaches are rated among the finest in the U.S. and draw tourists
from all over the globe. Florida’s visitors come to swim, surf, bask in the
sun, snorkel, fish and sail; and as a result, tourism has become the premier
industry in Florida, providing more than 845,000 jobs. In 1999 alone,
approximately 58.9 million tourists visited Florida, spending 46.7 billion
dollars. While development and tourism have been an economic boon to Florida,
they have also brought associated problems that must be continually addressed.
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