Water--Phosphorus content--Florida--Everglades

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.

Everglades restoration includes construction of six Stormwater Treatment Areas (STAs) totaling over 16,000 hectares. These filter marshes are designed to remove excess phosphorus from agricultural runoff and urban wastewater before it reaches the Everglades. Optimizing flow through these wetlands may be important in increasing the efficiency of nutrient removal and achieving lower outflow phosphorus concentrations. We measured periphyton growth and phosphorus uptake in two sets of replicated mesocosms in post-STA treatment water. Flow rates for the study were 1.0 cm s^-1 and 0.11 cm s^-1. Unique mesocosm design allowed for simultaneous control of loading rate, retention time and surface area, leaving flow rate as the single variable between treatments. Periphyton biomass accrual was 25% greater in the faster treatment. Measurements of dissolved oxygen were positively correlated with biomass accrual and there was no significant difference in the export of biomass between treatments.