Determination of final site elevation in terms of tidal range is critical 

 and should be based on precise knowledge of elevational requirements of the 

 plant communities. Final elevation of the marsh substrate is largely influ- 

 enced by settlement and consolidation of sediments. For a number of other 

 engineering and practical considerations see Coastal Zone Resources Corpora- 

 tion (1976) and Environmental Laboratory (1978), 



Plant propagation: Karsh developers may choose between natural invasion 

 and artificial propagation of plants. Natural invasion may be slow if there 

 is not an abundant nearby source of propagules. Sprigging increases costs but 

 can provide a quick cover and more rapid stabilization. Seeding is slower and 

 not as dependable as sprigging but is less costly. In an area like much of 

 California where natural colonization is \jery slow, sprigging or seeding may 

 be preferred over natural colonization. Natural invasion occurs much^'more 

 rapidly in freshwater situations than in saltwater systems. An artificial 

 marsh developed in the James River, Virginia, became densely vegetated without 

 artificial propagation within months following construction (Lunz 1977). A 

 detailed discussion of plant propagation considerations and techniques is pro- 

 vided in Environmental Laboratory (1978). Other useful information can be 

 found in Woodhouse et al. (1972), Kadlec and Wentz (1974), Wentz et al.(1974), 

 and Garbisch et al. (1975). 



Contaminant uptake : Heavy metal uptake by marsh plants and animals does 

 occur. Uptake of other contaminants has only rarely been reported for plants, 

 but has often been reported for animals. The most commonly reported heavy 

 metal uptake and biomagnification involves mercury. Windom et al.(1976) 

 studied a marsh contaminated with mercury and found uptake in the primary 

 consumers, Littorina i rrorata and Uca sp. , as well as in the secondary consum- 

 ers -- birds and mammals. Dunstan and Windom (1975) noted the tendency of 

 Spartina alterniflora to take up and concentrate mercury. Rhan (1973) noted 

 that S_^ a lterniflora took up mercury from sediments and released it to the 

 surrounding water through plant leaves. 



Trollope and Evans (1976) reported concentrations of five heavy metals 

 (copper, iron, lead, nickel, and zinc) in freshwater algae and Triniger (1977) 

 found high concentrations of cadmium in both aquatic plants and algae. Banus 

 et al. (1975) reported lead was taken up by S. alterniflora in concentrations 

 that ranged from 5.4 to 23.2 mg/1 , Lee et al.~ (1976) found that the several 

 marsh plant species, in which uptake was studied, concentrated most heavy me- 

 tals in below-ground portions. Lunz (1978) studied one artificial marsh and 

 two natural marshes and found concentrations of several hydrocarbons and heavy 

 metals in the soils. However, only nickel in the artifical marsh exhibited 

 significant uptake into tissues of marsh plants. Lee et al. (1978) found that 

 marsh plants growing on a wide range of dredged material disposal sites had 

 heavy metal levels similar to values reported for natural marshes. Dunstan and 

 Windom (1975) found lower concentrations of heavy metals in plants growing on 

 dredged material sites than in plants in natural marshes. They also found 

 lower concentrations of heavy metals (with the exception of mercury) in tis- 

 sues of S_^ alterniflora than in the sediments supporting the plants' growth. 

 Boyce (1976] states tFat it is not clear whether marsh plants vrHl take up 

 significant amounts of heavy metals from contaminated dredged material sub- 

 strates, or for that matter what constitutes significant uptake. Apparently 

 more work needs to be done to define the amount and significance of heavy 



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