The Wider Caribbean coastal zone contains many productive and biologically complex ecosystems. Nearshore marine habitats include coral reefs, seagrass beds, mangroves, coastal lagoons, beaches, and mud bottom communities. Of these, the coral reefs are the most visible and well researched. Their economic importance is partially tied to their value for fisheries and coastal tourism. The coastal ecosystems coexist through often complex and interdependent relationships, which are both physical and biological in nature. Coral reefs, seagrasses and mangroves in particular have evolved to become dependent on each other for survival. An effective coastal zone management strategy will have to be based on an understanding of the local marine and coastal habitats and their interactions.

Coral reefs

Coral reefs are among the most important coastal resources in the Wider Caribbean, and are also among the most productive. Coral reefs occur along most shallow, tropical coastlines, where the water is clear and warm, and the salinity is constant. There are around seventy species of corals in the Wider Caribbean. The reefs formed by these tiny colonial animals belonging to the phylum Cnidaria, and the calcium carbonate skeletons that they secrete, are the basis of many coastal fisheries. Corals provide food, shelter and nursery areas for many fishes and crustaceans. Reefs protect coastal areas from storms and erosion by forming natural breakwaters. Much of the white sand found on beaches originated from coral skeletons, or from the skeletons of creatures and algae associated with the reef. There are several different types of reef structures. Of these, fringing reefs occur next to the shoreline, while barrier reefs are separated from the coast by a wide lagoon. The lagoon is formed over time by faster reef growth on the seaward side of the reef, where the detrimental influences of land are not evident. Patch reefs are isolated clusters of corals, commonly found in the lagoon inside the main reef structure. Atolls are circular or semicircular reefs growing around islands that may be in the process of subsiding. Much of the tourism in the Caribbean consists of divers and snorkellers who are drawn by the beauty of the reefs and the beaches.

Seagrasses

Large seagrass meadows usually occur in the protected waters landward of coral reefs. Seagrasses are true flowering plants with the male and female flower capable of sexual reproduction ,although most of the reproduction is performed asexually via the rhizome system in the sediment. The two main seagrass species, the turtle grass (Thalassia testudinum) and the manatee grass (Syringodium filiforme), occur either in mixed or in monospecific beds. A few other species of seagrasses also exist in the Caribbean, but they are not as prevalent. Seagrass beds are productive environments. Grazers, such as green turtles, fishes, and sea urchins feed directly on the grasses. Seagrass blades provide surfaces for epiphytes like algae and invertebrates to attach on. Seagrass beds also serve as nursery grounds for the juveniles of many commercially important species, such as snappers, grunts, lobsters and conchs. Seagrasses help keep the water clear. The blades of the grasses act as baffles, inducing the settling of sediment particles, while the rhizome and root system stabilize the bottom, preventing the resuspencion of sediments. Clear water is an important requirement for the maintenance of healthy coral reefs.

Mangroves

Mangroves are found along the coasts of tropical and subtropical regions. The term mangrove refers to both the forest and the tree. The different mangrove species are not taxonomically related, but are grouped together because they can tolerate having their roots submerged in salt water. Their prop roots provide a surface of attachment for marine organisms in a muddy environment where hard surfaces are in short supply. Mangroves also trap and bind sediments and filter land based nutrients, promoting water clarity. Mangroves, like seagrasses, serve as nursery grounds for the juveniles of many commercially important fisheries species, while also providing habitat for a variety of small fishes, crabs and birds. Mangroves protect coasts against erosion by breaking storm waves and dampening tidal currents.

Estuaries, wetlands, watersheds and salinas

Coastal areas of the Wider Caribbean near major watersheds often contain large lagoons of fresh or brackish water. Estuaries, coastal lagoons, and other inshore marine waters are very fertile and productive ecosystems. They serve as important sources of organic material and nutrients, and also provide feeding, nesting and nursery areas for various birds and fishes. These ecosystems act as sinks of terrestrial run-off, trapping sediments and toxins, which may damage the fragile coral reefs. Salinas are found on many dry Caribbean islands. They are shallow ponds and lakes with limited water circulation and tidal contact. Traditionally, salinas have been used as salt evaporators, but more modern uses include mariculture operations and marina constructions. They function as sediment traps, protecting coral reefs from excessive sediment loading.

Beaches

The beach serves as a buffer zone between the land and the water. It is usually made up of unconsolidated sediments, such as sand, stones, coral rubble, and boulders. Beaches are dynamic environments, constantly changing as a result of natural processes, including storms, hurricanes, tidal changes, and sea level rise. Beaches also change as a result of man’s actions. Removing sand from the beach for construction, vegetation clearance, and building of seawalls are major problems in many areas of the Wider Caribbean. The major thrust of the Caribbean’s tourism industry is focused on this dynamic environment. Animals occupying this environment have adapted to the constant motion of the sand, gravel, or shell. Many important birds, reptiles, and other animals nest and breed on the berm and the open beach. Sea turtles use many beaches in the Wider Caribbean to dig their nests and deposit their eggs. The beach also provides habitat for a multitude of burrowing species, such as crabs, clams, and other invertebrates.

Mud bottoms

Mud bottoms support commercially important shrimp and groundfish fisheries, and are productive environments. Wide bands of relatively flat mud bottom are associated with the coasts of Central and South America. Mud bottom is also found in quiet bays and deeper basins, where fine sediments settle over time.