Forms and Lability of Phosphorus in Algae and Aquatic Macrophytes Characterized by Solution ³¹P NMR Coupled with...

Solution Phosphorus-31 nuclear magnetic resonance (³¹P NMR) spectroscopy coupled with enzymatic hydrolysis (EH) with commercially available phosphatases was used to characterize phosphorus (P) compounds in extracts of the dominant aquatic macrophytes and algae in a eutrophic lake. Total extractable organic P (P_o) concentrations ranged from 504 to 1643 mg kg^-1 and 2318 to 8395 mg kg^-1 for aquatic macrophytes and algae, respectively. Using ³¹P NMR spectroscopy, 11 P_o species were detected in the mono- and diester region. Additionally, orthophosphate, pyrophosphate and phosphonates were also detected. Using EH, phytate-like P was identified as the prevalent class of enzyme-labile P_o, followed by labile monoester- and diester-P. Comparison of the NMR and EH data indicated that the distribution pattern of major P forms in the samples determined by the two methods was similar (r = 0.712, p < 0.05). Additional ³¹P NMR spectroscopic analysis of extracts following EH showed significant decreases in the monoester and pyrophosphate regions, with a corresponding increase in the orthophosphate signal, as compared to unhydrolyzed extracts. Based on these quantity and hydrolysis data, we proposed that recycling of P_o in vegetative biomass residues is an important mechanism for long-term self-regulation of available P for algal blooming in eutrophic lakes.