Effect of Small-Scale Turbulence on the Growth and Metabolism of <i>Microcystis aeruginosa</i>

Abstract

Microcystis aeruginosa is a single-celled cyanobacterium, forming large colonies on the surface of freshwater ecosystems during summer, and producing a toxin (microcystin) that in high concentration can be harmful to humans and animals. These toxic effects can be governed by abiotic environmental conditions including water temperature, light, nutrient abundance, and fluid motion. We investigated the effect of small-scale turbulence on the growth and metabolism of Microcystis aeruginosa using field measurements and laboratory bioreactor investigations. The laboratory setup included two underwater speakers, generating a quasi-homogeneous turbulent flow with turbulent kinetic energy dissipation rates up to 10 −6 m 2 /s 3 , comparable to field values in the lacustrine photic zone. The role of turbulence is quantified by comparing cell number, dissolved oxygen production/uptake, and inorganic carbon uptake in stagnant condition and two sets of experiments with turbulent conditions, quantified by the Taylor micro-scale Reynolds number at Reλ = 15 and Reλ = 33. The results suggest that turbulence mediates the metabolism of Microcystis aeruginosa measured by the net oxygen production, oxygen uptake, and inorganic carbon uptake. Furthermore, small-scale turbulence marginally influenced Microcystis growth rate estimated from cell population concentration (−5% and 11% for Reλ = 33 and Reλ = 15, respectively, as compared to stagnant conditions).

The biomass of bloom-forming colonial Microcystis affects its response to aeration disturbance

“…It is generally believed that wind and wave disturbance contributes to the formation of Microcystis blooms in the shallow eutrophic Taihu Lake, China, and the main mechanism was that the wind and wave disturbance led to sediment resuspension and the utilization of nutrients by algae [31][32][33] . Thus, the influence of hydrodynamic disturbance on Microcystis blooms has not been fully studied 34 , which increases the complexity of hydrodynamic disturbance in regulating Microcystis blooms.…”

Numerical simulation of the vertical migration of Microcystis (cyanobacteria) colonies based on turbulence drag

“…However, this kind of dispersion is small even for the highest turbulence intensities experienced by Microcystis in the field (O'Brien et al, 2004). Some studies discussed the influence of turbulence on the ecology of Microcystis (Reynolds, 1994;Wilkinson et al, 2016). Their results suggested that M. aeruginosa are powerful enough to tolerate intensive mixing for a few days (>96 h) (Regel et al, 2004).…”

Rapid flotation of Microcystis wesenbergii mediated by high light exposure: implications for surface scum formation and cyanobacterial species succession

“…The sudden increases in biomass at the surface layer may lead to long-term proliferative cell interactions and mass migration of biomass. In many cases, this migration ends up forming thick scum on the surface of the water ( Anne et al., 2016 ).…”