marsh edges 

 shelter is 

 grass stans 

 pers. comm.) 



freshwater coastal marsh/ aquatic systems 

 represented by the Balize and Atchafalaya 

 Deltas are found to function in very much 

 the same way as saline estuaries, with the 

 same suite of marine/estuarine fish and 

 shellfish. In addi tion, freshwater species 

 like gars (Lepisosteus spp.), gizzard shad 

 Dorosoma cepedianum ), and blue catfish 

 Ictalurus furcatus ) are common (Kelley 

 1965, Thompson and Deegan 1983). 



Even when they are seldom found up in 

 the marsh itself or in the small marsh 

 ponds, other species concentrate along the 

 where food is abundant and 

 available in the streamside 

 For example, Peterson (LSU; 

 was unsuccessful in capturing 

 larval spotted sea trout until he began to 

 seine along the very edge of marshes as 

 compared to more open aquatic 



environments. Spotted sea trout are just 

 one example of the concentration of both 

 the food supply and the aquatic organisms 

 that depend on it. 



Biological activity is concentrated 

 at the marsh edge (Figure 56). For 

 reasons already discussed, pi ant production 

 is highest along the marsh edge. Finely 

 decomposed detritus from the previous 

 year's plant crop is flushed from the 

 marsh during the winter and accumulates 

 along the marsh edge in deep deposits 

 known to local shrimpers as "coffee 

 grounds." Nematode numbers are highest 

 here as are the concentrations of small 

 deposit feeders. It is no wonder that 

 larger invertebrates - shrimp and crabs - 

 and larval and juvenile fish are also 

 attracted to this feast. Virtually every 

 kind of organism enumerated has been found 

 to concentrate along marsh edges. 



Figure 56. 

 detritus and 

 salt marsh. 



Density of 

 consumers at the 



vegetation , 

 edge of the 



The importance of this energy flow 

 pathway in marshes can be seen 

 qualitatively by comparing the list of 

 nektonic species in Figure 54 that use the 

 benthic pathway predominantly with those 

 that use the planktonic pathway. Of the 

 abundant species only the gulf menhaden, 

 the bay anchovy, and the juvenile Atlantic 

 croaker are filter feeders. Crabs, 

 shrimp, drum, gar, mullet and nearly all 

 the small resident marsh fish are benthic 

 feeders. 



This benthic food pyramid is the 

 dominant one in salt marshes. Meiofauna, 

 particularly nematodes, graze the bacteria 

 on decomposing grass, are ingested in turn 

 by deposit feeders which are a major 

 source of food to nektonic fish, shellfish 

 and birds. The marsh-dependent fish, 

 especially the \/ery small ones, graze and 

 shelter up in the marsh when it is flooded 

 and lie in the small marsh ponds and along 

 the edges of fine feeder creeks at other 

 times. As they grow they frequent deeper, 

 more open water. 



Wildlife 



Wildlife species that use Mississippi 

 delta marshes are abundant. Table 22 sum- 



marizes 



taxonomic 



found in 



chenier 



Louisiana 



the same 



richness 



the species of different 

 groups that are likely to be 



different marsh zones in the 

 plain region of southwestern 

 The deltaic plain has about 

 species. In general, species 

 is highest in the fresh marsh, 

 decreasing into saline areas. No amphibi- 

 ans and only 4 reptile species are found 



63 



