The transformation of the nutrient in the degradation process of the phytoplankton-derived particulate organic matter and it's ecological effect

The phytoplankton-derived particulate organic matter was taken in Lake Taihu as the breakthrough point. We studied the changing process of the C, N & P elements in the degradation process of the phytoplankton-derived particulate organic matter under the different environmental conditions (light or dark), and analyzed the role of phytoplankton-derived particulate organic matter in the nutrient water cycling and the growth of phytoplankton. During the cyanobacteria blooms, the contents of C, N & P in the phytoplankton-derived particulate organic matter can account for 81.51%, 94.60% and 97.47% of the total content in the water respectively at most, and they were the important parts of the nutrient elements in the water. The APA under the light condition was significantly higher than that in the dark, which showed that the rate of degradation and transformation of P in the particulate organic matter under the light condition is significantly higher than that in the dark. However, the concentration of SRP under the light condition was less than that in the dark and the concentration of Chl-a was higher. The algae grew along with the degradation of the particulate organic matter under the light condition, absorbing the SRP in the water and converted to biomass. The light had a significant impact on the degradation of the C, N & P, for the degradation rates of the C, N & P in the dark were twice that in the light, and the proportion of degradable in the dark was 2.5±0.1 times of that in the light. The degradation of each element during the first seven days was higher than that after the seventh day. In conclusion, the nutrient in phytoplankton-derived particulate organic matter with high yield gross, biological availability, rapid degradation, and degradation products could be assimilated by the phytoplankton, was the important nutrient sources of algae growth. © 2016, Chinese Society for Environmental Sciences. All right reserved.