The rigorous environment of the salt marsh sharply limits the number of 

 animals living there. These areas are used by birds such as herons, rails, 

 sandpipers , geese , ducks , and songbirds and by raccoons . A much larger popu- 

 lation of animals lives in or on the mud surface. The more conspicuous are 

 fiddler crabs, mussels, clams, and periwinkles. Less obvious but more 

 numerous are annelid and oligochaete worms and insect larvae. In addition, 

 larvae, juveniles, and adults of many shellfish and fish are commonly found in 

 the marsh creeks. 



Little is known of the animal populations and the feeding relationships in 

 high marsh. 



b. 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, 1978). Under some circumstances, 

 smooth cordgrass will increase growth in response to fertilizer applications 

 of as much as 672 kilograms of nitrogen (N) and 74 kilonewtons of phosphorus 

 (P20c) per hectare per year (Woodhouse, Seneca, and Broome, 1974, 1976). 

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

 shoot growth alone, a value that compares favorably with upland field crops. 

 The potential for substantial recycling and exporting of nutrients to the 

 estuary exists. The absorption, conversion, and recycling capabilities of 

 marsh plants offer real opportunities for water purification (Woodhill, 1977). 



c. Esthetics . Marshes are a visual transition between land and water and 

 a natural feature of the landscape adding form, color, and texture to the 

 shore. Unlike other forms of shore protection, once plants are established 

 there remains no visible evidence that there has been a human effort to reduce 

 erosion as illustrated by Figure 37. In addition, the unique assemblage of 

 birds and mairanals which are associated with marshes are of interest and are 

 often subjects of photographic and illustrative art forms. Standard 

 structural methods of shore protection may visually alter the shoreline (Fig. 

 38), creating a barrier rather than a transition between land and water. 



2. Potential Negative Impacts . 



a. Public Access . Vegetative stabilization discourages certain recrea- 

 tional activities. Vegetation discourages public access for water-oriented 

 activities such as swimming, wading, and sunbathing. In addition, vegetation 

 discourages fishing from the shore; oth6r shore protection structures often 

 provide a platform for fishing use. 



b. Heavy Metal Release . There has been concern expressed that inter tidal 

 marshes are a mechanism for releases of potentially toxic, heavy metals to 

 estuarine systems and the ocean. This is a subject of extreme complexity. 

 Gunnison (1978) has recently summarized existing information on mineral 

 cycling in marsh-estuarine ecosystems. 



In general, the release of heavy metals is not a major concern for shore 

 stabilization projects unless sediments with high levels of heavy metals are 



85 



