An Improved Logistic Model Illustrating Microcystis aeruginosa Growth Under Different Turbulent Mixing Conditions

Haiping Zhang,Fan Huang,Yuehong Zhang,Feipeng Li,Ruihong Chen,Zhujun Gu

doi:10.3390/w11040669

Haiping Zhang, Fan Huang + Show 4 more

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https://doi.org/10.3390/w11040669

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Abstract

To overcome the limitations of the normal logistic equation, we aimed to improve the logistic model under hydrodynamic conditions for the examination of the responses of cyanobacterium, coupled turbulence mixing, and growth of cyanobacterium in population dynamics models. Selecting Microcystis aeruginosa and experimenting with the ideal conditions in a laboratory beaker, the chlorophyll-a concentration reached the corresponding maximum under each turbulent condition compared with the control. According to the experiment results, the theory of mass transfer, turbulence mixing, and the logistic equation are organically combined. The improved logistic growth model of Microcystis aeruginosa and competition growth model in the symbiont Scenedesmus quadricauda under turbulent conditions were established. Using the MATLAB multi-parameter surface fitting device, both models produced good fitting effects, with R > 0.95, proving that the results fit the models, and demonstrating the relationship of the unity of nutrient transfer and algae growth affected by turbulence mixing. With continuous increases in turbulent mixing, the fitted curve became smoother and steadier. Algae stimulated by turbulence accelerate reproduction and fission to achieve population dominance. The improved logistic model quantitatively explains the Microcystis aeruginosa response to turbulence and provides a basis to represent ecological and biogeochemical processes in enclosed eutrophic water bodies.

Highlights

In hypertrophic freshwater lakes, turbulent mixing is increasingly thought to be a key factor in the growth, blooms, and composition of the cyanobacterium Microcystis aeruginosa [1,2,3,4]
The growth responses of cyanobacterium compared to the flow velocity and corresponding nutrient uptake obtained from laboratory experiments are often contradictory [11]
Without considering the velocity of mechanical damage, small-scale turbulence strongly influences the growth of Microcystis aeruginosa

Summary

Introduction

Turbulent mixing is increasingly thought to be a key factor in the growth, blooms, and composition of the cyanobacterium Microcystis aeruginosa [1,2,3,4]. Due to the complex interactions between algae physiology and behavior, nutrient dynamics, and the light environment, many studies failed to accurately characterize these inhibitory effects in nature [10,11]. To qualitatively describe algae dynamics and correlation with turbulent mixing, researchers have conducted series of. The growth responses of cyanobacterium compared to the flow velocity and corresponding nutrient uptake obtained from laboratory experiments are often contradictory [11]. These conflicting results are due to many studies using qualitative analyses, and due to the adopted flow velocity, which can only represent the average algal environment rather than the environment surrounding the cells

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