Dynamics of particulate phosphorus in a shallow eutrophic lake

摘要

We tested the hypothesis that in shallow, eutrophic Lake Kasumigaura, the concentration of particulate phosphorus (PP) is controlled by biogenic P (P in living or dead phytoplankton and bacterial cells), rather than by resuspension of inorganic P in sediment. Increases in wind velocity and turbidity were associated with bottom shear stress exceeding the critical value for the lake (t_c = 0.15 N m~(-2)); this increased turbidity was due to sediment resuspension. However, concentrations of PP; HCI-extractable, reactive P in PP (P-rP); and HCI-extractable, non-reactive P in PP (P-nrP) were not correlated with wind velocity (PP vs. wind velocity: r = 0.40, p ＞ 0.05). Rather, the P-nrP concentration accounted for approximately 79% of PP, and the concentrations of PP, P-rP, and P-nrP were correlated with the particulate organic carbon (POC) concentration (POC vs. PP: r = 0.90, p ＜ 0.01; POC vs. P-rP: r = 0.82, p ＜ 0.01; POC vs. P-nrP: r = 0.86, p ＜ 0.01). In our ~(31)P nuclear magnetic resonance spectroscopy results, mononucle-otides accounted for the largest proportion among the detected P compound classes. In addition, concentrations of mononucleotides, orthophosphate, and pyrophosphate were significantly higher in samples with high POC concentrations, whereas the DNA-P concentration was not These results suggest that biogenic P affects PP concentrations more strongly than does sediment resuspension, and the production of biogenic P creates a pool of mononucleotides, a class of easily degradable P, even in shallow, eutrophic Lake Kasumigaura.