Macrophyte species changes in the everglades: Examination along a eutrophication gradient

Macrophyte species distribution in the marsh and slough areas of the northe rn Everglades mere examined along a surface mater and soil P gradient to ch aracterize the effects of nutrient enrichment on the macrophyte community c hanges in the Everglades ecosystem. Macrophyte species distribution and fre quency examined at 51 sites located in the Water Conservation Area (WCA-2A) revealed distinct trends in species changes with P enrichment. Marshes in the unentrends ; and enriched areas were dominated by Cladium jamaicense an d Typha domingensis, respectively. Open water areas were characterized by E leocharis sp., Utricularia sp., Chara zeylanica, and Nymphaea odorata in th e unenriched areas and by floating plants and Polygonum sp. in the enriched areas. We compared the macrophyte species distribution with the soil P con tour map of WCA-ZA and derived six major categories of P enrichment (labele d 0-5) that may be used to adequately describe macrophyte species distribut ion in the WCA-2A. Soil and surface water P values that correspond to the d ifferent P-enrichment categories and the number of macrophyte species in ea ch category have been estimated. Examination of the relative abundance of t he macrophyte species in the six P-enrichment categories showed a decline i n characteristic slough macrophyte species with P enrichment. Increase in P status of the system was also accompanied by the advent and gradual establ ishment of macrophytes such as Mikania scandens, Sarcostemma clausum, Polyg anum sp., A crostichum danaeifolium, and a variety of floating plants. Char acteristic slough macrophyte species such as Utricularia purpurea, Eleochar is elongata, and Eleocharis cellulosa serve as indicators of the unenriched P conditions.