Effects of mixing intensity on colony size and growth of Microcystis aeruginosa

Zhong Chunni,Steven W Wilhelm,Rui Zheng,Yang Hongwei,Qin Boqiang,Yang Guijun,Liu Yu,Zhang Zhou,Han Lihua

doi:10.1051/limn/2019011

Abstract

Mixing is an integral environmental factor that affects lake ecosystems. For the cyanobacterium Microcystis, colony size is important with respects to migration velocity, how cells respond to grazing pressure, light attenuation, nutrient uptake and growth. To understand how mixing shapes colony size and the growth of Microcystis, we measured the effects of different current velocities (0, 0.16, 0.32, 0.64, and 1.28 m s−1) on M. aeruginosa in Lake Taihu. After 24 h of continuous mixing, the mean colony sizes of M. aeruginosa in the controls, 0.16, 0.32, 0.64, and 1.28 m s−1 groups were 23.6, 50.1, 92.9, 67.8, and 37.3 μm, respectively. Colony sizes of M. aeruginosa in all treatment groups were significantly larger than those in controls. As well, the concentration of soluble extracellular polysaccharide and bound extracellular polysaccharides of M. aeruginosa in all treatment groups were significantly higher than those in controls. Except for the highest level of mixing (1.28 m s−1), the growth rate of M. aeruginosa was significantly higher than that in controls. This study suggested that mixing intensity over short time periods can significantly influence colony size and the growth of M. aeruginosa.

Highlights

The formation of cyanobacterial blooms is one of the most troubling symptoms of eutrophication (Sommaruga et al, 2009)
analysis of variance (ANOVA) showed that the mean colony sizes of M. aeruginosa in 0.16, 0.32, 0.64 m sÀ1 groups were significantly larger than those in controls (P < 0.01), but no significant difference between mean colony size of M. aeruginosa in controls and the 1.28 m sÀ1 groups was found (P > 0.05)
An ANOVA showed that the colony sizes of M. aeruginosa in all treatment groups were significantly larger than that in control (P < 0.05) in the first day in this experiment

Summary

Introduction

The formation of cyanobacterial blooms is one of the most troubling symptoms of eutrophication (Sommaruga et al, 2009). The mean colony sizes of M. aeruginosa in controls, 0.16, 0.32, 0.64, and 1.28 m sÀ1 groups were 23.2 (±1.8), 35.7 (±1.2), 51.6 (±2.6), 40.8 (±4.3), and 25.7 (±2.4) mm, respectively (Fig. 1a). In the first day in this experiment, the colony size of M. aeruginosa in 0.16, 0.32, 0.64, and 1.28 m sÀ1 groups increased after continuing mixing for 24 h.

Results

Conclusion