disposal and bank erosion associated 

 with this channel have caused the 

 direct loss of over 24,000 acres of 

 forested wetlands, coastal marsh and 

 associated shallow estuarine waters 

 (U.S. Fish and Wildlife Service 

 1980). Leveeing of the Mississippi 

 River has disrupted historical pro- 

 cesses of overbank flooding and dis- 

 tributary flow, thereby depriving 

 coastal marshes of fresh water, 

 nutrients and sediments. Reduced 

 freshwater inflows, in combination 

 with navigation channels, have 

 resulted in saltwater intrusion and 

 a reduction in quality of existing 

 marsh habitat. 



Serious declines in swamp and 

 marsh habitat have resulted in 

 severe impacts on fish and wildlife 

 resources and it is anticipated that 

 these losses will continue in the 

 future. Reduction in habitat has 

 led to decreases in populations of 

 wildlife, including resident and 

 migratory waterfowl, wading birds, 

 shorebirds, furbearers and a variety 

 of small and big game animals. These 

 losses have led to decreases in com- 

 mercial fur harvest and reduced op- 

 portunities for activities such as 

 waterfowl, big game and small game 

 hunting. 



Saltwater intrusion has caused 

 drastic changes in plant and animal 

 communities. Fresh-intermediate 

 marshes have been converted to more 

 saline types and some areas of wood- 

 ed swamp have been entirely elimi- 

 nated. These changes in habitat 

 types have seriously altered the 

 structure of wildlife communities. 

 Conversion of fresh-intermediate 

 marshes to more saline types has re- 

 sulted in elimination of valuable wa- 

 terfowl habitat and has also reduced 

 populations of important furbearers 

 such as muskrat ( Ondatra zibethica) 

 and nutria (Myocastor coypus ) . 



Loss of coastal marshes has 

 also adversely impacted the produc- 

 tion of fish and shellfish species. 

 In coastal Louisiana, the majority 

 of commercially important fish and 

 shellfish species are estuarine- 

 dependent, with juveniles utilizing 

 the estuaries as nursery areas. 

 Marshes provide a source of organic 

 detritus, a vital component of the 

 estuarine food web; the importance of 

 marsh vegetation as a source of 

 organic detritus has been well docu- 

 mented (Darnell 1961, Odum et al. 

 1973). 



Increases in salinity levels in 

 Louisiana estuaries have reduced 

 availability of low salinity nursery 

 habitat important to penaeid shrimp 

 ( Penaeus spp.), blue crabs (Cal- 

 linectes s apidus ) , Atlantic croakers 

 (Micropogon undulatus ) and menhaden 

 ( Brevoortia spp.). Saltwater intru- 

 sion has also eliminated habit.it 

 important to the American oyster 

 ( Crassostrea virginica). Salinities 

 exceeding 12-15 ppt permit the south- 

 ern oyster drill ( Thais haemostoma ) 

 and other oyster predators to move 

 in over oyster reefs. In addition, 

 saltwater intrusion has caused areas 

 suitable for oyster cultivation to 

 shift inland and closer to sources 

 of pollution. This has led to more 

 frequent oyster reef closures by 

 public health officials. 



In order to ameliorate these 

 problems, the New Orleans District 

 of the U.S. Army Corps of Engineers 

 has undertaken studies to investi- 

 gate the diversion of fresh water 

 from the Mississippi River to coast- 

 al areas of Louisiana. Two promi- 

 nent studies being undertaken are 

 entitled "Mississippi -Louisiana 

 Estuarine Areas Study" (MLEA) and 

 the "Louisiana Coastal Area Study" 

 (LCA). The MLEA study area is lo- 

 cated in southeastern Louisiana, 



377 



