totally inshore so both catch and 

 economics are dependent on coastal 

 features. 



There is little doubt that marshes 

 export organic matter in the form of young 

 fish that enter the marshes as larvae, 

 postlarvae, or juveniles in early summer. 

 During the warm part of the year they grow 

 rapidly, becoming better able to survive 

 in coastal waters in the autumn (Werme 

 1981). Turner (1977) has shown that there 

 is a significant correlation between the 

 areal extent of subtidal and regularly 

 flooded intertidal vegetation in an 

 estuary and the size catch of the inshore 

 shrimp fishery in the Gulf of Mexico. 

 Successful commercial blue crab fisheries 

 are associated with salt marshes as are 

 sport fisheries (Pomeroy and Wiegert 

 1981). 



A timely visit to most salt marshes 

 along the Atlantic coast will convince a 

 visitor that the marsh killifish is an 

 important food source for wading birds and 

 as such provides the basis for an export 

 in the form of heron and egret biomass. 

 In Georgia, the bird biomass similarly 

 exported may be that of the white ibis 

 which seemed, in one Georgia nesting area, 

 to be feeding almost exclusively on grass 

 shrimp from salt marshes (Teal 1965). 

 Black ducks feed extensively on Hydrobia 

 and Melampus from salt marshes. Canada 

 geese are very attracted to and take a 

 significant amount of Spartina production 

 from salt marshes in Cape Cod (Buchsbaum 

 et al. 1982). 



6.3 POLLUTANTS AND MARSHES 



6.3.1. Heavy Metals 



Marsh sediments act as filters and 

 tend to accumulate heavy metals. Most 

 heavy metals form insoluble sulfides, and 

 are sorbed onto clays, organics, and 

 precipitates such as iron hydroxides. The 

 marsh sediments have high sulfide 

 concentrations so that the insoluble metal 

 sulfides tend to be deposited in the 

 sediments and accumulate there. As a 

 result of several decades of research on 

 the behavior of heavy metals in salt 

 marshes, much is now known about what 

 actually takes place when heavy metals 



arrive in salt marshes. The interested 

 reader should look at reviews by Giblin 

 et al. (1980), Nixon (1980), Giblin 

 (1982), and Teal et al . (1982). 



Sea level has been continuously 

 rising since the retreat of the Pleisto- 

 cene glaciers. This regular rise makes it 

 possible to assign approximate dates to 

 core depths independent of dating the 

 material in the core itself. Figure 26 is 

 a profile of lead found in cores from New 

 England marshes. The concentrations in- 

 creased dramatically toward the surface, 

 i.e., in the more recently deposited 

 sediments. This increase began about the 

 time market hunting of shore birds in the 

 marsh was prevalent and was accelerated 

 during industrialization. The present 

 high level is correlated to the burning of 

 leaded gas in automobiles. The high sam- 

 ple value from the Neponset River Marsh 

 was taken near a major highway (Banus et 

 al. 1974). A similar profile has been 

 found in other marshes (Siccama and 

 Porter 1972; McCaffrey 1977). These 

 marsh studies all indicate that as 



% Below - Ground Biomass 



i I 3 , 1 i 6 " Pb tppm, ACID SOL BASIS) 



20 40 60 80 100 120 „ 3 



Figure 26. Lead distribution and 

 concentration in cores from New England 

 salt marshes (Banus et al. 1974). 



46 



