Sediment . Sediment storage in the salt marsh may be partitioned into two 

 components: bottom sediment and suspended sediment. Flows in and out of the 

 system are suspended in water. The root system and dead standing crop of vege- 

 tation are responsible for trapping some of this suspended sediment; the 

 deposition of sediment results in an increase in elevation. Successional 

 phenomena are dependent upon this aggradation (Wells, 1928; Penfound, 1952; 

 Lambert, 1964). 



Exogenous mineral materials are of greater importance than peat accumula- 

 tions in the salt marsh sediments. The ranges of average organic matter content 

 of salt, brackish, and fresh marshes in Louisiana are 2 to 26 percent, 26 to 

 49 percent, and 6 to 66 percent, respectively (Chabreck, 1972). Brupbacher et 

 al. (1973) reported the average organic matter contents of 45, 50, and 66 percent 

 from salt, brackish, and fresh marshes, respectively. Thus salt marshes tend 

 to accumulate organic material, although to a lesser extent than other marsh 

 ecosystems (Chabreck, 1972; Brupbacher et al., 1973). Nutrients bound to these 

 sandy and silty clays may provide a significant contribution to the storage of 

 nutrients in the systen . 



Suspended sedinients may affect the system via two pathways. The most direct 

 pathway involves siltation effects. Bottom flora (algae, diatoms) and fauna 

 (burrowers, oysters) may be partially or completely covered. The turbidity 

 Jue to suspended sediment may decrease primary productivity by decreasing the 

 light energy available to photosynthetic organisms. 



Nutrients . The sources of nutrients in the salt marsh include exogenous 

 (fresh and salt wattr) dissolved organic and inorganic material, nitrogen fix- 

 ation, and detritus. Unavailable nutrients can be converted to available 

 nutrients by two main processes. The bulk of nutrient regeneration (converting 

 complex organic molecules to simple, usable forms) is accomplished by bacteria 

 and protozoa. The important nutrients involved include phosphate and ammonia 

 (Day et al., 1973; De Laune et al., 1976). The second nutrient conversion pro- 

 cess is submergence and the release of extractable nutrients. This process 

 affects the availability of nitrogen, iron, manganese, phosphorus, potassium, 

 magnesium, calcium, sulfate, and chloride. The actual increases in available 

 forms of nutrients are highly variable and depend upon complex chemical character- 

 istics of the soils (Brupbacher et al., 1973; De Laune et al., 1976). De Laune 

 et al. (1976) reviewed the literature and provided further data that indicate 

 nitrogen may be the limiting nutrient in salt marshes. Although the quantity 

 of total nitrogen present may be large, the plants are dependent on the available 

 nitrogen (ammonia), which is provided by algae and bacteria via nitrogen fixation 

 and regeneration. Thus, the rate of production of ammonia may be the limiting 

 factor involved. 



Primary producers . The vegetation of salt marshes is surprisingly similar 

 along the entire Atlantic and gulf coasts (Allan, 1950; Cottam and Bourn, 1952). 

 Smooth cordgrass is the dominant grass. Black needlerush ( Juncus roemerianus ), 

 saltwort ( Batis maritima ), glasswort ( Salicornia spp. ), saltqrass ( Distichlis 

 spicata ), and marshhay cordgrass ( Spartina patens ) are angiosperms commonly 

 found associated with the dominant, but always on the higher, better drained 

 areas. 



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