Phosphorus dynamics of a Florida freshwater marsh receiving treated wastewater.
A study was made of the effect of secondarily treated effluent on the phosphorus budget of a central Florida freshwater marsh. Three 2000 m2 plots received effluent at the rates of 1.3, 3.8 and 10.2 cm wk-1, while a fourth control plot received 3.8 cm wk-1 of freshwater. In the first year the plot receiving the high rate of effluent showed increased net production of plant shoots, increased litter production, increased root and rhizome production and higher phosphorus concentrations in living and dead plant tissue compared with the control plot. Effluent treatments did not significantly increase the phosphorus concentrations measured in the groundwater draining from the experimental plots, which had phosphorus concentrations c 97% less than the phosphorus concentration of the applied effluent. Phosphorus budgets were constructed for the control plot and the plot receiving the high effluent treatment. Over the course of the study 38.03 g P m-2 were applied to the high effluent plot. Of the total input 26.31, 8.81 and 1.97 g P m-2 were stored in the soil, roots and rhizomes, and litter respectively. Outflow of phosphorus from the plot amounted to only 0.94 g P m-2. The freshwater control plot received a total of 0.38 g P m-2. Storage in the litter accounted for 0.21 g P m-2 and outflow accounted for the remaining 0.17 g P m-2. There was no evidence of a spring flush of phosphorus from either the control or effluent plot.