Modelling the vertical migration of different-sized Microcystis colonies: coupling turbulent mixing and buoyancy regulation
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Exceptional vertical migration ability provides the cyanobacterium Microcystis with competitive advantages in bloom formation and dominance establishment. Studies have been conducted on the vertical migration patterns of Microcystis since the 1970s; however, bloom simulations remain limited. Here, we used a simple model based on the viscous drag force of turbulence and analysed the motion characteristics of Microcystis colonies. The vertical distribution of turbulent kinetic energy (KZ), cell concentration and colony size profiles in Lake Taihu (Meiliang Bay and Gonghu Bay) and the critical vertical turbulent kinetic energy of colonies (TKZ, i.e. the anti-turbulence ability of colonies) were tested. The results showed that, under steady KZ profiles, colonies had relative rest positions (RRPs) where KZ ≈ TKZ and colonies of the same size gathered together. The vertical migration patterns were affected more by turbulence than by density (colony mass density) if the average KZ of the water column (MKZ) was not equal to TKZ. If MKZ ≈ TKZ, the colonies could exhibit a diurnal pattern of sinking at noon and floating upwards before dawn without steady RRPs. Our results suggest that studies on RRPs may offer optimizations for bloom forecast and control in the future due to easier simulation of KZ profiles than that of flow fields.
KeywordsViscous drag force of turbulence Relative rest position Vertical migration Colony size Turbulent kinetic energy Microcystis
The project was funded by the Program on Furtherance of Scientific Research of Japan, Fundament C [15K00630], the National Natural Science Foundation of China [Grant 51409216] and the Taihu Lake water pollution control special funds (Tenth Phase) scientific research topic [JSZC-G2016-198].
- Chen Y, Qian X, Zhang Y (2009) Modelling turbulent dispersion of buoyancy regulating cyanobacteria in wind-driven currents. International Conference on Bioinformatics and Biomedical Engineering, pp 1–4Google Scholar
- Dong CY, Luan WL, Zhou ST, Zhang Q (2007) Analysis and application of model for solid particle movement in Newton fluid. J China Univ Pet Ed Nat Sci 31:55–63Google Scholar
- Joung SH, Kim CJ, Ahn CY, Jang KY, Boo SM, Oh HM (2006) Simple method for a cell count of the colonial cyanobacterium, Microcystis sp. J Microbiol 44:562–565Google Scholar
- Kromkamp J, Konopka A, Mur LR (1988) Buoyancy regulation in light-limited continuous cultures of Microcystis aeruginosa. J Plankton Res 13:173–183Google Scholar
- Walsby AE (1970) The nuisance algae: curiosities in the biology of planktonic blue-green algae. Water Treat Exam 19:359–373Google Scholar
- Walsby A (1994) Gas vesicles. Microbiol Rev 58:94–144Google Scholar
- Xiao M, Zhu W, Li M, Sun Q, Nkrumah PN, Tan X (2013) The influence of water oscillation on the vertical distribution of Microcystis colonies of different sizes. Fresenius Environ Bull 22:3511–3518Google Scholar
- Zanke UCE (2003) On the influence of turbulence on the initiation of sediment motion. J Sediment Res 18:17–31Google Scholar
- Zhao HR, Zhu W, Chen HM, Zhou XH, Wang RC, Li M (2017) Numerical simulation of the vertical migration of Microcystis (cyanobacteria) colonies based on turbulence drag. J Limnol 76:190–198Google Scholar