175 



rate of sea level rise and the rate of change of marsh level due to 

 sedimentation or erosion. In intertidal freshwater zones, encroaching 

 salinity will kill bottomland hardwood forests (cypress and gums) and 

 freshwater marsh plants (Odum et al., 1984). These will be replaced by 

 brackish-water grasses and shrubs (Stout, 1984), such as sawgrass (Cladium 

 jamaicense ) , giant cutgrass ( Zizaniopsis miliaceae) , giant cordgrass 

 ( Spartina cynosuroides ) , and saltmarsh bullrush ( Scirpus robustus) . These 

 brackish plants will then be replaced by more saline species of salt marsh 

 plants (Teal, 1986), such as saltmarsh cordgrass ( Spartina alterniflora ) 

 and black needle rush (Juncus roemerianus ) . In south Florida, mangroves 

 ( Rhizophora mangle . Avicennia germinans . and Laguncularia racemosa) should 

 replace brackish grasses (Odum et al . , 1982). Salt marshes and mangroves 

 will be replaced by intertidal mud and sand flats and then by open water 

 over submerged benthic ecosystems (Peterson and Peterson, 1979) . If light 

 can penetrate to the bottom and currents are not too erosive, seagrasses 

 will probably develop on submerged sediments . 



The extent of inland movement of any particular ecosystem depends on 

 the inland movement of marine conditions and the effectiveness of inland 

 systems to resist invasion or expand seaward. Competition amongst the main 

 structure -defining species of adjacent systems may be important in 

 determining future horizontal extent of each ecosystem. 



Island systems and coastal hardwood hammocks will be especially 

 vulnerable to sea level rise.^ For a circular island or hammock, the area 

 of dry land will be reduced in proportion to the square of the reduction in 

 radius. Low relief islands and hammocks will disappear first along with 

 any habitat value they may have for resident and migratory birds and other 

 wildlife. 7 



Coral reefs may also be particularly vulnerable to sea level rise if 

 the rise is accompanied by an increase in turbidity. In clear water, 

 vertical growth of coral reefs can keep up with rising sea level because of 

 calcification resulting from the photosynthesis of symbiotic zooxanthellae 



^T.J. Smith and W.M. Kitchens, comments on Chapter 11, see appendix. 



■^L. Harris, Dept. Wildlife and Range Sciences, Univ. Fla., personal 

 communication. 



