Home Preface Synopsis History of the Study Regional System Ecosystems - Freshwater and Terrestrial > Coastal   -  Sandy beaches   -  Mangroves & salt marshes   -  Estuaries & bays   -  FL. reef tract - Man-dominated Hydrologic Systems Final Word References Appendices PDF version

The south Florida coastline can be divided into four ecological areas: sandy beaches, mangroves and salt marshes, shallow bays, and the Florida reef tract. These areas blend from one to another. Mangroves and sand extend from the shoreline into the bays, and the bay-bottom grass beds spread out past the Florida Keys onto the reef tract.

Water is the medium that links the coastal ecosystems. Saltwater from offshore currents moves over the reef tract, through the bays and mangroves, and back offshore carrying physical and biological products from one coastal environment to another. Freshwater, moving overland from the mainland through the mangroves, into the bays, and out to sea, transports terrestrial products to marine habitats. Where moving water acquires sufficiently different characteristics, it supports different plant and animal communities.

The Florida Current, moving around the tip of Florida and continuing northward as the Gulf Stream, provides clean, warm, saline water to the coastal area, water that helps produce the conditions required for coral formation and that supports a diverse tropical marine flora and fauna. In addition, the Florida Current transports and distributes juvenile fish and invertebrates, as plankton, to coastal water.

Tidal currents flush oceanic water in and out of the bays, mixing it with freshwater from rains and terrestrial runoff. The sediments and shallowness of the bays encourage the growth of extensive marine grass beds. These grass beds are highly diverse and productive habitats adapted to some fluctuation in salinity and temperature. The bays themselves derive some of their nourishment from the mangrove and salt marshes and tidal flushing and terrestrial runoff.

Any major change in the coastal environment will have an effect throughout the coastal ecosystem. Diminishing nutrient production in one part of the system will show up as less biological production in another part, and disturbed sediments are often redistributed, smothering a distant habitat. In addition, alteration of freshwater runoff changes the distribution of coastal salinity.