|Biotic and abiotic uptake of phosphorus by periphyton in a subtropical freshwater wetland|In: Aquatic Botany. Elsevier Science: Tokyo; Oxford; New York; London; Amsterdam. ISSN 0304-3770, more
Kinetics; Nutrient deficiency; Oligotrophic lakes; Periphyton; Phosphorus; Radioisotopes; Uptake; USA, Florida, Everglades Natl. Park [Marine Regions]; Fresh water
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Phosphorus (P) demand in extremely oligotrophic shallow water wetlands often exceeds supply and maintains water chemistry in a P-limiting condition. Phosphorus uptake by the calcareous periphyton community in the oligotrophic Florida Everglades was examined. Phosphorus removal from solution was used to obtain uptake parameters for epipelon, epiphyton, and metaphyton. Nutrient ratios (C:N:P) were higher in epiphyton compared to metaphyton or epipelon but all periphyton types were P-limited. Michaelis-Menten kinetic experiments resulted in Km values ranging from 8.5 to 16.4 µM and Vmax values ranging from 0.24 to 0.74 µmol g-1 dry weight min-1, in the order epiphyton, metaphyton, epipelon. Removal of inorganic P (Pi) as KH2PO4 and dissolved organic P (Po) as ATP from solution was best described by a first-order equation with rate constants ranging between 0.02 and 0.17 min-1. The values of Km were greater than ambient dissolved reactive P (DRP) concentrations (<0.2 µM); therefore Vmax is not reached under normal field conditions. The hydrolysis of Po as ATP was rapid, being >0.67 µmol g-1 DW min-1. After hydrolysis Po uptake was similar to Pi uptake. It was hypothesized that P adsorption with CaCO3 in the periphytic matrix would add to the removal of P from solution. Using H332PO4 and [32P]ATP and a 0.01 M HCl extraction technique, P incorporated by epipelon was partitioned into biotic and abiotic compartments. The biotic compartment contained >83% of the incorporated P after 12 h incubations. Biological demand exceeds abiotic adsorption in this P-limited system but adsorption mechanisms are responsible for a portion (<15%) of water column P removal.