is impossible to optimize both sediment input and salinity in the park. The implementation of 

 the Davis Pond diversion and changes to restore natural hydrology will be very beneficial in dealing 

 with any saltwater problems. 



Management Implications of Sediment Dynamics 



The importance of mineral sediment input for wetland health has been highlighted during the 

 last two decades (DeLaune et al. 1978; Baumann 1980; Hatton et al. 1983; Baumann et al. 1984). 

 Mineral sediment input increases wetland elevation, enhances primary productivity, and thus organic 

 accretion in wetlands. Both of these accretionary processes are often necessary to offset inundation 

 occurring in subsiding areas. Studies of sediment accretion in Barataria Basin wetlands show that 

 this area is experiencing a sediment deficit (Baumann 1980; Hatton et al. 1983; Baumann et al. 

 1984). Jean Lafitte National Park is also experiencing a sediment deficit, especially in those inland 

 ar^as and areas behind spoil banks. Thus, new sediment and mineral input must be enhanced in 

 this area to encourage healthier vegetation and firmer substrate. 



Management of the park should include plans to enhance sediment input during frontal passages 

 when southerly winds push water into the basin and water with high suspended sediments 

 concentrations (often greater than 100 mg/L) floods marshes. These sediments settle and accrete 

 in the marshes. Weirs in Pipeline and Tarpaper Canals would decrease the rapidity of the water 

 exchanges and allow the sediments to settle within the canal and in the marshes. 



The proposed SCS management plan for the park included plug and weir placement along the 

 Segnette Waterway, which would have resulted in semi-impoundment and sediment exclusion from 

 the park. Based on results of this study, open access of park wetlands to both resuspended and 

 diverted sediment sources is of high priority to the health and maintenance of the area. 



Management Implications of Altered Hydrology 



Disturbance of natural sheet flow through the wetlands and impoundment of cypress swamps are 

 two of the major hydrologic alterations which have occurred in the park. Considerable research 

 shows that impoundment as a management practice for cypress swamps results in lowered 

 productivity and regeneration (Conner et al. 1981). The swamp in the park will disappear if 

 management practices are not changed. Overland sheet flow from the bottomland hardwood 

 forests to the cypress swamps and into fresh and intermediate marshes should be encouraged 

 (Figure 11). Structures in pipelines and canals will moderate rapid water level fluctuations. Canal 

 spoil banks that impound the cypress swamps and marshes should be breached and perhaps 

 eliminated. 



Resilience and Management Implications of Floating Marshes 



There is relatively little information about floating marsh productivity and resilience in Louisiana. 

 The productivity of floating Panicum marshes ranges from 1,700 g/m 2 /yr to 1,960 g/m 2 /yr (Sasser 

 et al. 1981; Sasser and Gosselink 1984) as compared to 1,501-2,310 g/m 2 /yr for freshwater Saggitaria 

 lancifolia marshes (Hopkinson et al. 1978). Secondary production of fish and other aquatic 

 organisms is probably less in floating marshes than in stable marshes due to low 2 , high CO-, and 

 low pH below the mat (Howard-Williams and Gaudet 1985). Alligators, deer, and mammals do, 

 however, use elevated floating marshes and wax myrtle stands as habitat. 



Determining whether floating marshes are ephemeral or resilient ecosystems within a 

 management time frame is important for decisions concerning wetland management. In some cases, 

 floating marshes have persisted for long periods. Sasser (Center for Wetland Resources, Louisiana 



268 



