Assessing Bioavailability of Typical Lakes and Reservoirs in Northeast China Based on Phosphorus Fractions

To explore the eutrophication degree in the typical lakes and reservoirs of the northeast region of China, the bioavailability of dissolved organic phosphorus (DOP) of the lakes has been examined in this study. The laboratory incubation was carried out at 20 °C for 55 days and the concentrations of total dissolved phosphorus (TDP), dissolved reactive phosphorus (DRP), DOP and the microbial biomass have been detected. Results showed that, during the process of incubation, the concentrations of TDP and DRP were increased, whereas the DOP was decreased, which leads to the decreased mineralization rate. In addition, the changes of microbial biomass were fluctuant, but they had significantly positive effects on the concentration changes and mineralization rate of DOP (p < 0.05). The correlation analysis among the phosphate fractions showed that the TDP significantly promoted the DRP concentration, mineralization rate of DOP and the cumulative mineralization of DOP. The kinetics model was conducted to predict the further mineralization of DOP and to analyze the pollution degree of the eight lakes and reservoirs. Accordingly, the lakes with high DRP and TDP had worse water quality and are prone to algae blooms.