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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.