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estuarine environments throughout this region. Coral reefs and 

 mangrove swamps are the typical coastal features of south Florida, 

 while the islands are mountainous and are fringed with coral reefs 

 and beaches. Tidal ranges are small. 



Gulf Coast Estuarine Region : Cape Romano to the Mexican border. 



A wide continental shelf extends all the way around this large 

 embayment, in which warm tropical waters are moved gently by weak 

 currents and small tidal ranges. Heavy rainfall over most of the 

 area brings sediments from the broad coastal plain to be deposited 

 in the estuarine zone. Most of the drowned river valleys have 

 evolved to a point intermediate between those of the Middle and 

 South Atlantic Regions -- harrier islands are extensive and have 

 large shallow bays behind them. 



The Mississippi, carrying drainage from 41 percent of the conter- 

 minous land mass of the United States, forms one of the major deltas 

 of the world and is unique among the estuarine systems of the 

 United States, both in its size and in the extent to which it has 

 built out over the continental shelf. 



Pacific Southwest Estuarine Region: Mexican border to Cape 

 Mendocino. 



Because of the narrow continental shelf, periodic upwelling of deep 

 water close inshore as winds force the California current offshore 



