Waterflow through the park has been drastically transformed. A combination of agricultural, 

 urban, industrial, and drainage activities have created an altered ecosystem dissected by modified 

 bayous and dredged canals. Surplus water flows into channelized bayous or dredged canals and is 

 diverted into open water. 



Canal systems short-circuit many of the natural water flows. Much runoff now bypasses wetlands 

 within the park. When nutrient-laden waters enter water bodies directly, nutrient uptake and 

 removal processes are insufficient to reduce nutrient loads, and eutrophication often results (Day 

 et al. 1977, Craig and Day 1981). Spoilbanks retard water and material exchange and cause 

 prolonged flooding and stagnation leading to decreased productivity and species changes (Conner 

 and Day 1976; Hopkinson and Day 1980). 



Habitat Changes 



There were significant habitat changes in the park between 1956 and 1983 (Figures 2 and 3; 

 Table 1; U.S. Fish and Wildlife Service 1983). In 1956, there were 2,385 ha of fresh marsh, 470 ha 

 of bottomland hardwood forest, 614 ha of forested swamp, and 98 ha of forested and developed 

 upland. The emergence of large stands of Myrica cerifera by 1983 indicates that park drainage 

 patterns had been altered. A study by Michot (1984) showed that the scrub/shrub areas 

 experienced the shallowest fall water levels (3.83 cm) reflecting either higher elevations or floating 

 conditions. The conversion of 1,322 ha of fresh marsh to intermediate marsh and the emergence 

 of a small number of inland open water areas probably resulted from subsidence and salinity 

 increase. 



Floating Wetland Terminology 



Because much of the park is a floating wetland, it is important to define terminology referring 

 to floating wetlands carefully. "Flotant" or "floating marsh" is a fresh marsh mat which oscillates 

 freely with the water layer beneath it (O'Neil 1949). "Tremblant" is a floating brackish marsh 

 (O'Neil 1949). "Quaking marsh" is a form of marsh intermediate between a stable marsh and 

 floating marsh. A quaking marsh experiences some mat movement, yet because of vegetative 

 connections with the substrate beneath it, does not oscillate freely with water levels. 



METHODS 



Establishment of Study Plots 



Sixteen study plots were established throughout the park in an effort to encompass the range 

 of habitat conditions which exist (canal, firm marsh, floating marsh, swamp, and areas affected by 

 spoil banks; site locations are in Figure 4). In establishing these plots, we used aerial imagery, Soil 

 Conservation Service Conservation Treatment Units (CTU) (Figure 5), discussions with park 

 representatives, and field observations. Sites 4, 5, 6, 10, and 15 were selected for studying the 

 effect of the spoil banks on the inland marsh characteristics. Marsh and swamp hydrologic stations 

 were placed 50 m inland to characterize typical habitat in the absence of spoil and habitat behind 

 a continuation of spoil bank widths. All sites were monitored monthly for hydrology, salinity, and 

 soil substrate characteristics. Sites 5, 6, 9, 12, 17, and 18 were also examined for sedimentation 

 rates. 



Marsh Elevation and Marsh Water Depth 



Vertical movements of the marsh surface and water depth over the marsh were measured 

 monthly. Between mid-May 1986 and early April 1987, wetland elevation and surface water depth 



250 



