Of the Sunshine State’s 8,426 miles (13,560 km) of tidal shoreline, approximately 825 miles (1,328 km) consist of sandy beaches, primarily along Florida's east coast. Though the state’s Gulf beaches are renowned for their sugar-white sands, the northeastern beaches of Florida, including those in the northern Indian River Lagoon area, are composed principally of quartz originating in the Appalachian Mountains. Further south, the amount of quartz in sand decreases steadily, and sand composition becomes primarily calcium carbonate from rock and shell deposits.
Abiotic factors such as wave action, erosion, sand accretion by winds, overwash, and the deposition of salt spray are physical processes that contribute to beach and dune formation.
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. Waves deposit sand on beaches as they break, lose energy and retreat. Hurricanes can erode sands and carry them offshore, or overwash dunes and deposit sand inland.
In the IRL, 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. But during fall and winter, the steep waves that accompany storms erode beaches and flatten the profile, depositing eroded sands seaward on longshore bars.
Biotic factors generally center around the ability of plants to colonize and grow, which stabilizes the beach and its dunes. Colonizing species of plants must be able to tolerate the xeric conditions that result from sand being generally well-drained and low in nutrients, as well as frequently being buried in sand or inundated by sea water.
Intense wave action, strong winds, and the presence of sea water make it difficult for many species of plants to 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.
Most beach plants occupy the pioneering zone, which extends landward from the wrack line on the upper beach through the dune area. Pioneering species are highly specialized to tolerate the punishing environmental challenges they face: very dry (xeric) conditions, heavy winds, low nutrient availability, high soil temperatures and burial in sand.
The most successful pioneering species in coastal zones are halophytic, or able to thrive in highly saline conditions. Many of these same plants also have high growth rates; some plants actually grow faster as they become buried in sand.
Pioneering species are also generally vine-like or succulent, with waxy or hairy coverings on their stems and leaves. They produce many seeds that are widely dispersed, helping them to become quickly established or recolonized on beach areas. They tend to spread widely as they grow, creating a network of creeping stems so if one part of the plant is uprooted or buried in shifting sand, the remaining segments can continue to grow.
Pioneering plants’ roots also help to anchor sand, and thus assist in subsequent dune building and stabilization.
At first glance, beaches may appear to support comparatively few animal species. But beyond birds and reptiles, there are a great many other species – they’re often just too small or furtive to chance upon casually.
Many species utilize beaches as feeding areas. Sandpipers and other shorebirds, wading birds, and even some fish such as the Florida pompano (Trachinotus carolinus) 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.
These 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 (variable coquina) and mole crabs are two species commonly seen in the surf zone. Both animals are extremely fast burrowers, able to rebury themselves almost as fast as they become exposed in shifting sands. Further up the beach, somewhat removed from intense wave action, the ghost crab makes its home by burrowing into the sand.
Although many species of birds are often observed on beaches, most visit for feeding. Only five species of shorebirds prefer nesting sites on bare sands in the upper beach zone, including the snowy plover, black skimmer, least tern, royal tern and sandwich tern. Snowy plovers nest only along the Gulf coast of Florida.
The Florida coastline is the most important nesting area for sea turtles in the western Atlantic. Six of the world’s seven species of sea turtles are dependent on Florida beaches for nesting during the summer.
In Florida, loggerhead turtles and green turtles are by far the most common. Loggerheads lay an average of 3,000 to 4,000 nests per year; green turtles lay approximately 300 nests per year.
The highest sea turtle nest densities occur in southern Brevard County, from south of Cape Canaveral to Sebastian Inlet; however, 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 relocate the eggs to other areas to ensure successful hatching.
Some mammals also exploit beaches for feeding. Raccoons, feral cats and foxes patrol the wrack line at the high-water mark for morsels, and scavenge eggs from sea turtle nests.