Macrophyte Slough Community Response to Experimental Phosphorus Enrichment and Periphyton Removal

In this chapter, we will present evidence that may help in explaining the general pattern of response of wetland macrophyte communities to eutrophication, light, and competition as well as assess changes in plant responses to alterations in water depth in open water sloughs. Importantly, we utilized our P dosing experiment to determine the long-term effects of a large range of P enrichments on the slough macrophyte community. Our primary objective was to determine the effect of experimental P enrichment on mortality and vigor of Utricularia purpurea, Eleocharis elongata, Eleocharis cellulosa, and Nymphaea odorata, the main species in our test sloughs. To further aid in the confirmation of macrophyte trends observed in the experimental mesocosm study, we also transplanted these key species in control and highest P-enriched channels to lend insight into the mechanism affecting mortality associated with enrichment and to “calibrate” the mortality and senescence of U. purpurea as a function of PO₄ concentration to assess the use of this species as a potential indicator organism. To investigate the effect of short-term reduced algal community competition, we did a removal experiment in which the periphyton mat, the epiphytic algae, or both were removed for 6 months to assess the effects on macrophyte growth of E. cellulosa, N. odorata, and U. purpurea within an unenriched Everglades slough community near the dosing study in WCA-2A. We hypothesize that removal of periphyton mechanically would result in increased macrophyte growth due to increased light availability.