In addition, larvae, junveniles, and adults of many shellfish and fish 

 are commonly found in the marsh creeks. 



Little is known of the animal populations and the feeding relation- 

 ships in the high marsh. 



b. Protection . Quantitative documentation on the value of marsh 

 vegetation in reducing shore erosion is limited to a few recent plant- 

 ings. However, a number of these plantings have demonstrated that the 

 development of a full cover of marsh grasses can reduce or eliminate 

 erosion by trapping sediments and damping the impact of waves (Woodhouse, 

 Seneca, and Broome, 1974, 1976; Garbisch, Woller, and McCallum, 1975) 

 (Figs. 5, 6, and 7). More information will be available as the number 



of experimental and applied plantings increases. Many stable estuarine 

 shorelines have a natural protective cover of marsh vegetation. Also, 

 the natural stabilization of the intertidal fringes of dredged material 

 deposits in bays and estuaries by vegetation has long been observed. 



Marshes are by no means impervious to erosion. They are particu- 

 larly vulnerable to undercutting below the waterline and may be over- 

 come by persistent high-energy wave action. The older, high marsh 

 becomes very susceptible to erosion as it builds up a thick layer of 

 peat which elevates the living marsh. This often results in the develop- 

 ment of a vertical scarp and the progressive undermining of the marsh 

 edge. Thousands of kilometers of Juncus marsh in the estuaries of the 

 South Atlantic and gulf coasts are presently eroding; large areas of 

 high marsh have been lost in this way (Fig. 8). 



The value of the damping action of marsh vegetation on the movement 

 of water entering bays and estuaries as a result of storm surges is 

 difficult to assess. The effect is small where marsh occupies a narrow 

 fringe along steep shorelines but can be substantial in large, shallow, 

 gently sloping marsh areas. 



c. Nutrient Cycling . Salt marshes have substantial absorptive 

 capacities for potential pollutants such as nitrogen, phosphorus, and 

 heavy metals (Williams and Murdock, 1969; Woodhouse, Seneca, and Broome, 

 1974). Increased growth of salt marsh species, particularly smooth 

 cordgrass, in response to nutrients has been noted at several locations 

 (Valiela and Teal, 1974; Woodhouse, Seneca, and Broome, 1974; Garbisch, 

 Woller, and McCallum, 1975; Patrick and Delaune, 1976; Mendelssohn, 



in preparation, 1978). Under some circumstances, smooth cordgrass 

 will increase growth in response to applications of as much as 672 

 kilograms of nitrogen and 74 kilograms of phosphorus per hectare per 

 year as fertilizer (Woodhouse, Seneca, and Broome, 1974, 1976). 

 Apparent recovery of applied nitrogen may be as high as 40 to 60 



