consumers, which are significant economic resources in coastal industry in 

 Maine, depend upon the primary production of the salt marsh grasses. 



Impacts, such as destruction of wetlands by dredging and filling, on the 

 energy flow in salt marsh habitats ultimately will affect those plants and 

 animals that depend upon salt marsh production for their energy requirements. 

 Similarly, the overharvesting or destruction of any components of the food web 

 will affect the species that depend upon those components as a food source. 



Energy flow models and food webs aid in understanding the complex 

 interrelationships in an ecosystem. Managers must be cognizant of the 

 intricate patterns of energy flow from the primary producers to the highest 

 consumers in order to assess adequately the impacts of particular activities 

 on estuarine intertidal salt marshes. 



Globally, estuarine intertidal wetlands have been postulated to have critical 

 roles in maintaining and controlling the cycles of sulfur and nitrogen (Deevey 

 1970). On a regional level, tidal marshes exhibit an excess of stored 

 phosphorus in the sediments yet lack the vital nitrogen component for maximum 

 growth. Since salt marsh sediments contain enough phosphorus in the upper 33 

 feet (10 m) to promote normal plant growth for 500 years salt marshes do not 

 appear to be phosphorus-limited (Pomeroy et al. 1969). 



Little research has been done on biogeochemical cycling in Maine salt marshes. 

 McGovern and coworkers (in press ; and 1978) studied salts secreted by 

 cordgrass and the elements in the leaves of cordgrass that potentially could 

 enter the estuarine detrital food web. 



Reimold (1972) reported that cordgrass in Georgia is a vehicle to translocate 

 phosphorous from salt marsh sediments to estuarine waters. McGovern and 

 coworkers (in press ) found that a stand of cordgrass with a biomass of 1.0 

 kg/m could export 1.0 g P/m /hour. 



Although it appears that cordgrass in Maine may not contribute as much 

 phosphorous to the estuarine system as populations farther south, the high 

 productivity of Maine's salt marsh cordgrass and the export of almost all of 

 the above-ground senescent biomass to the water column yield a large quantity 

 of nutrients. McGovern (1978) determined the elemental composition of 

 cordgrass and subsequently the amounts of these nutrients that enter the 

 estuarine water column annually in a Maine salt marsh. They were nitrogen, 

 0.993 g-atoms/m ; phosphorous, 0.075 g-atoms/m- ; potassium, 0.218 g-atoms/m? ; 

 calcium, 0.144 g-atoms/m"; magnesium, 0.330 g-atoms/nf ; iron, 0.030 g-atoms/ 

 iir;boron, 1681.0 g-atoms/m^; copper, 281.0 g-atoms/m ; and manganese, 2634.0 

 g-atoms/m2 . This represents a significant contribution to the estuary from 

 the cordgrass of the intertidal emergent wetland habitat. No data are 

 available concerning the contribution of other salt marsh species (salt hay 

 and black rush) to the estuarine water column. 



Little data are available on nutrient levels in the salt marsh peats and in 

 the contiguous water column in Maine. It generally is agreed that nitrogen is 

 the key nutrient limiting growth in the salt marsh plants (Pomeroy et al. 

 1969; and Sullivan and Daiber 1974). Nitrogen, applied to the marsh in the 

 form of urea or ammonium nitrate, caused increased production of almost all 

 plants in a Massachusetts salt marsh (Valiela and Teal 1974). 



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