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Dynamics of particulate phosphorus in a shallow eutrophic lake

Shinohara, Ryuichiro, Imai, Akio, Kohzu, Ayato, Tomioka, Noriko, Furusato, Eiichi, Satou, Takayuki, Sano, Tomoharu, Komatsu, Kazuhiro, Miura, Shingo, Shimotori, Koichi
The Science of the total environment 2016 v.563-564 pp. 413-423
bacteria, eutrophication, inorganic phosphorus, lakes, nuclear magnetic resonance spectroscopy, orthophosphates, particulate organic carbon, phosphorus, phytoplankton, sediments, shear stress, stable isotopes, turbidity, wind speed
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 (τc=0.15Nm−2); this increased turbidity was due to sediment resuspension. However, concentrations of PP; HCl-extractable, reactive P in PP (P-rP); and HCl-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 31P nuclear magnetic resonance spectroscopy results, mononucleotides 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.