areas, though Adkins and Bowman (1976) have not found this increase 

 in every circumstance. 



The water pathway afforded by the canal may permit an acceleration 

 of freshwater runoff from the marsh (Copeland and Dickens, 1974; 

 Darnell, 1976). The result may be a lower water table under the 

 marsh surface, and eventually drier conditions in high marsh areas. 



Spoil placement may block existing small drainages so that the marsh 

 may be effectively impounded. This may result in localized changes 

 in runoff and standing water. Plants may be exposed to increased 

 salinities and acid conditions. In other instances, however, the 

 resulting impounded area may have less saline conditions and contain 

 plants characteristic of fresh marshes (Conner et al., 1976). Thus, 

 the total area affected is site specific and could range from insig- 

 nificant to highly significant when compared to the total area of 

 marsh. 



Replacement of marsh soil and vegetation by deep bodies of water 

 (canals and wellsites) creates new habitat with attendant community 

 changes. In the canal, algae increase while marsh vegetation is 

 eliminated. Net primary production of algae will probably increase 

 (Corliss and Trent, 1971). However, the total net primary produc- 

 tion will decrease (Darnell, 1976) because of elimination of other 

 marsh plant types. 



The number of aquatic consumers may decrease or increase in the 

 canals (Bourn and Cottam, 1950; Adkins and Bowman, 1976). Measures 

 of total biomass have generally shown a decrease (Trent et al., 

 1972). Shifts in relative species abundance will be evident; species 

 indicative of deep aquatic habitats will increase compared to typical 

 marsh species (Lindall et al., 1973; Dale, 1975; Adkins and Bowman, 

 1976). However, turbidity that results from chronic erosion can 

 decrease the suitability of the standing water as habitat for phyto- 

 plankton, aquatic invertebrates, and fish. 



Some areas of brackish marsh have little standing water upon them 

 except during storms or periods of exceptionally high tides. The 

 communities in these areas may be those most altered by canal excava- 

 tion. 



The spoil from canal excavation is usually subaerial, though with 

 slumping and spreading the edges may become subaqueous. These edges 

 may support marsh grasses after a few years. The higher areas may 

 have growths of marshhay cordgrass if the soil is damp and saline, 

 or marsh elder and groundsel on drier ground. 



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