But they afford protection to the estuaries behind them, where the salt marshes remain fairly stable, with human encroachment their worst threat. At the southern tip of Florida is a rich marine environment supported by a vast estuarine nursery system that has suffered tremendously from the abuses of over-zealous land developers. At lower end of the Florida peninsula are coral islands and reefs on the Atlantic side and a maze of mangrove forests and islands on the Gulf side. This is also the rearing and feeding grounds for 75 percent of the sport fishes and 90 percent of the commercial species taken in this part of the state. Long, narrow, sandy barrier islands and reefs skirt the coast of the Gulf of Mexico from northwestern Florida to Brownsville, Texas.
Estuaries here are generally broad and shallow, flanked by extensive marshlands.
Along the Texas coast, barrier islands have nearly enclosed narrow estuarine lagoons, leaving only small openings to the gulf. Those with major freshwater inflow are subjected to widely varying salinity levels, while several that receive only minimal fresh water are actually hypersaline. On the Pacific Coast, San Francisco Bay is the only estuarine system similar to the large eastern estuaries, both because of its physical makeup and the dense urban and industrial development along its shores. The North-Pacific Region extends from northern California to Alaska and contains some 40,000 miles of tidal coastline. Most coastal rivers here drop quickly from the mountains to the sea and culminate in relatively small estuaries.