These two conflicts, between renewable and non- 

 renewable resources, and between private and public 

 benefits, are the root of most of the environmental 

 problems discussed ui part 3. Understanding the way 

 wetlands function, in particular their close coupling 

 with adjacent uplands and estuarine areas and the 

 Gulf of Mexico, and the importance of the integrity 

 of the hydrologic system in a basin is the first step to 

 intelligent management of resources. 



4.3 SALT MARSH HABITAT 



Salt marshes have been extensively studied and 

 are probably the best understood wetland habitat, yet 

 few studies have been conducted on the narrow salt 

 marsh zone of tlie Chenier Plain. Studies in basins 

 east of the Chenier Plain supply much of the pertinent 

 data by inference. 



Salt marsh habitat is not widespread in the 

 Chenier Plain (fig. 4-20). Perhaps this is because the 

 wetlands of this region have been cut off from the 

 direct influence of Gulf waters by a relatively con- 

 tinuous beach and ridge complex. Tidal passes are few 

 compared to the much more open eastern Louisiana 

 subdelta region, and influx of saline waters is cor- 

 respondingly restricted. As a consequence most of the 

 inland wetlands are brackish to fresh, rather than 

 saline. 



Salt marsh habitats are, for the most part, a high- 

 energy wetland habitat in the Chenier Plain. Tidal 

 inundation is frequent, and sometimes occurs as often 

 as twice a day. Compared to many salt marshes, 

 salinities are rather low (about 12%o) with charac- 

 teristically large daily and seasonal variability. Salini- 

 ties are highest during late summer when rainfall is 

 low and Gulf water levels are high (part 33). Con- 

 versely, during spring floods fresh water from over- 

 flowing rivers freshens the salt marsh. 



4.3.1 PRODUCERS 



Of the wetland habitats, the salt marsh supports 

 the smallest number of plant species (table 4.6). In 

 the Chenier Plain, saltgrass is the donrinant species, 

 while smooth cordgrass, blackrush, and saltmeadow 

 cordgrass make up a smaller percentage of the total 

 plant composition. The sea ox-eye daisy is found only 

 at elevations above normal tidal action (spoil banks, 

 for instance) and the saltwort, a halophyte, prefers 

 highly saline sediments and grows in the upper reach 

 of the tide where storms carry in salt, which is then 

 concentrated by evaporation. Alligatorweed and bull- 

 tongue are found at the interfaces with lower salinity 

 marshes. 



Table 4.7 shows estimated annual production for 

 salt marshes in Louisiana to be about 2,200 g/m^ . This 

 is extremely high production compared to most natural 

 ecosystems. Epiphytes and benthic algae are also 

 abundant (appendix 6.3). Primary productivity of 

 epiphytes and benthic algae has not been measured in 

 the ChenierPlain region, butStowe(1972) determined 

 seasonal rates for epiphytes on smooth cordgrass in 

 Barataria Bay, Louisiana (appendix 6.3). His data in- 

 dicate a net production peak during summer months 

 and a minimum during winter months. However, ab- 

 solute production levels were not high; gross produc- 

 tion was 27 g/m^/yr for an inland community and 

 104 g/m^/yr along a stream bank. Over the year, res- 

 piration of the inland community exceeded produc- 

 tion by a factor of three, showing that the epiphyte 

 community is not self-sustaining, but depends on other 

 organic sources in the marsh. Recent gas flux mea- 

 surements indicate that production by the microbial 

 components of a smooth cordgrass community was as 

 much as 9% of the total community photosynthesis 

 during the winter but less than 5% in the summer 

 (Gosselink et al. in press). Emergent plants produce 

 the bulk of the energy upon which animals of the salt 

 marsh habitat depend. 



Table 4.5 Numbers of vertebrate consumer species reported to use the different wetland habitats. 



Consumer species^ 



Wetland habitat types 



Salt 



Brackish 



Intermediate 



Fresh 



Swamp 

 forest 



Impounded 



Total 



112 



5 

 16 



40 

 17 

 15 

 17 

 11 



121 



6 

 16 



43 

 16 

 16 

 16 

 11 



124 



18 

 24 



19 

 32 



23 

 36 

 11 

 15 

 25 



161 



16 

 28 



59 



21 



6 



1 



14 



145 



Many of these species use both marsh and open water habitats ;many require large ranges for day to day movement and seasonal 

 foraging for food. 



172 



