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11. COASTAL ECOSYSTEMS 



11.1 INTRODUCTION 



As sea level continues to rise, perhaps at an anthropogenically 

 accelerated rate, existing coastal ecosystems will become submerged and 

 saline water will move inland. Furthermore, tidal amplitude and wave 

 energy may increase due to submergence of protective nearshore reefs and 

 sandbars and other effects (see sections 4 and 5). Water level, water 

 motion, and salinity are principal determinants of the type, nature, and 

 function of coastal ecological systems. Therefore, changes caused by 

 rising sea level could cause dramatic changes in coastal ecosystems. 



Coastal ecosystems include open water systems, submerged benthic 

 (bottom) systems, intertidal systems, and supratidal systems. Open water 

 systems consist of plankton (suspended organisms transported by the 

 current) , neuston (organisms dwelling in or near the surface film) , and 

 nekton (actively swimming organisms). Benthic systems include coral reefs, 

 seagrass ecosystems, and ecosystems of unvegetated sediments. Mud and 

 sandflats that are periodically exposed, and marshes and mangroves are 

 common intertidal systems. Supratidal systems include coastal hardwood 

 hammocks and bottomland hardwood forests. Each of these coastal systems is 

 valued for its contribution of food and cover to the production of a 

 diversity of living coastal resources (Haines, 1979; Peterson, 1981; 

 Zieman, 1982; Odum et al . , 1982; Boesch and Turner, 1984; Seaman, 1985). 

 It is likely that a mix of coastal habitats is more important to these 

 resources than any one system alone. 



Ecological production (i.e., primary production) in coastal zones is 

 equal to or greater than that obtained with the best mechanized 

 agriculture, yet without the subsidies of plows and chemicals (Odum, 1971). 

 Coastal zones have been said to have natural energy subsidies that together 

 with sunlight account for this very high level of production, namely, the 

 water movement caused by tides, winds, and freshwater discharge (Schelske 

 and Odum, 1961; Odum, 1980). 



