Author(s): Qian Yu, Yongcan Chen, Zhaowei Liu, Na Li
Linked Author(s): Zhaowei Liu
Keywords: : Hydrodynamic turbulence, microcystis, sensitivity analysis, vertical distribution, modeling
Abstract: Microcystis blooms, which not only harm aquatic ecosystems but also threaten human and animal health, are worldwide problems. Modeling of Microcystis vertical distributions is very important to understand blue-green bloom formations and its competition for resources with other algae. In this paper, a new coupled model of simulating vertical population dynamics of Microcystis by coupling advection-diffusion equation and buoyancy regulation is developed. This coupled model includes a total of 10 parameters. A sensitivity analysis is conducted on these parameters to identify the key factors that impact on Microcystis vertical dynamics. According to numerical simulations, it is found that the vertical distributions of Microcystis and the corresponding mechanisms are different under different flow regimes with different turbulent diffusion coefficients (D). Hence, we conduct a sensitivity analysis in relatively calm water (D=0. 17cm2/s) and in turbulent water (D=400cm2/s), respectively. The results of the sensitivity analysis show that the diameter of Microcystis colonies (d) and the form resistance of colony () play different roles in calm water and in turbulent water, respectively. Both d and have much bigger influences in calm water than in turbulent water, which is due to different mechanisms of Microcystis vertical distributions. In calm water, self-migration of Microcystis determines the vertical distributions that most of Microcystisfloat upwards and gather on the surface of water. d and are the main factors that impact on the vertical velocities of Microcystis. Hence, they have significant influences on population distributions in calm water. On the contrary, it is flow turbulence that determines the population dynamics in turbulent water. That is, Microcystis would distribute relatively uniform in the vertical. Therefore, the algae with faster net growth rate would take the advantage. Hence, the maximum growth rate and loss rate have more important impacts in turbulent water
Year: 2017