Dispersal of mangroves is by floating seeds. Called propagules, seeds, mature and begin growing while stil on the tree. Each propagule develops an elongated body that becomes the trunk of the seedling. When the propagule is mature, it drops from the tree and may lodge in the soil directly, where it will begin to grow. How ever, if it does not stick, it will float, on its side first. After several days, it begins to change buoyancy and floats veritcally. Finally, after several weeks, it sinks. If, by chance during the course of its tidal travels, it becomes lodged in a calm area shallow enough for growth, it rapidly sprouts roots from the bottom and initial two leaves from the top.
Where they are protected from erosion, mangrove swamps are often soil builders. As generations of mangroves live and die, their prolific root systems and varying loads of leaf and twig litter become peat, which can rise to the level of high tides. When sea level rises slowly, as it has during the past 3,000 years, mangrove swamps can keep up with the rise and become elevated by these soil-building processes.
Mangrove swamps can be extremely productive. Given the right combination of tidal flushing (movement of water and suspended material in and out of the swamp) and freshwater runoff, mangrove swamps are among the most productive natural communities in the world. The ecological values of the mangrove swamp arise from the fate of its products: the leaves, twigs, bark, pollen, and so forth. As these materials decompose, they become food for marine life. Mangrove detritus (the dead plant debris with attached microorganisms) is eaten by many species at the base of an extensive food web, including shrimp, larval crabs, and small fish. In fact, the excellent fisheries of the Florida Keys, Florida Bay, and the eastern Gulf of Mexico owe much to the mangroves of Everglades National Park. Not only do the mangrove swamps provide a food source, but combined with the associated tidal creeks and bays, act as a nursery ground for a great many marine species.
Mangroves have been a focus of federal, state, and county legislation in Florida, most of which emanated from studies that began in the late 1960s and pointed out the great ecological benefits that mangrove swamps provide to man and wildlife alike. Mangrove swamps had long been recognized for their role in shoreline stabilization, particularly during hurricanes, because the take the initial rage of storm-tossed seas and thus protect man’s interests farther inland.