Phosphorus uptake rates of a Ceratophyllum/periphyton community in a southern Florida freshwater marsh

Net uptake rates of soluble reactive phosphate (SRP) of Ceratophyllum demersum and the dense periphyton mat associated with the macrophyte were calculated by measuring the disappearance of stable phosphorus (30, 50, 100, or 200 μg P/L) from the water column over a one-hour period each month for one year. Two seasonal periods were established based on average photosynthetically active radiation (PAR) and length of daylight through the year. ANOVA showed that the uptake rates were significantly affected (P < 0.05) by the amount of SRP added and were greater during the period of increased irradiance. Uptake rates continued to increase, even at spike concentrations equal to 10,000 μg P/L, indicating that maximum uptake was not achieved and that this plant complex is able to sequester even greater amounts of SRP. Estimates of the yearly uptake capabilities of the plant complex for a 525 ha wetland for the 30, 50, 100, 200 μg P/L spike treatments were 27, 55, 103, and 182 kg P/yr, respectively.