Periphyton--Florida--Everglades

Differences in relative primary productivity of periphyton were determined for three light regimes: open slough (control), sawgrass canopy, and cattail canopy. The center of Water Conservation Area 2-A, Everglades was chosen as the study site because it is relatively unaffected by nutrient runoff. Periphyton productivity was determined by the light and dark bottle method, and biomass was recorded as ash-free dry weight. Statistically significant correlations were found between periphyton biomass and water temperature and between organic content and water temperature. Mean photosynthetically active radiation reaching the surface of the water under sawgrass and cattail canopy was 45% $\pm$ 3% and 11% $\pm$ 1% respectively. Relative primary productivity of periphyton was lower under cattail canopy than under sawgrass canopy due to increased shading of cattail. This reduction of periphyton biomass and primary productivity can be considered an indirect effect of nutrient enrichment from the Everglades Agricultural Area.

Analysis of the relationship of velocity to taxonomic composition of periphyton-based stormwater treatment areas, in conjunction with other metrics, is a valuable tool for evaluating the phosphorus removal efficiency of this Everglades restoration advanced treatment technology. Periphyton taxonomic composition, biomass, water and tissue total phosphorus (TP), pH, and temperature were analyzed in three slow velocity (0.22 cm s-1) and three fast velocity (2.0 cm s-1) mesocosms. Loading rate, retention time and surface area were kept constant, with velocity the single variable between treatments. There was no significant difference in taxonomic composition, water TP, tissue TP, or temperature between the slow and fast treatments. However, dominant eutrophic and oligotrophic indicator genera exhibited significant and consistent changes in relative abundance related to location along the treatment path. Biomass accrual was 30% greater in the fast treatment and TP uptake was positively correlated with increased velocity.