Differences in vertical distribution of Microcystis morphospecies composition in a shallow hypertrophic lake (Lake Taihu, China)

Abstract

Cell density, morphospecies and colony size of Microcystis at different depths in Lake Taihu were investigated from spring to winter 2011 to identify differences in Microcystis morphospecies compositions at different depths and their causes. Microcystis ichthyoblabe, Microcystis wesenbergii and Microcystis aeruginosa successively dominated the water surface from June to October. However, the percentage of both M. wesenbergii and M. aeruginosa did not exceed 50 % in the mesosphere when M. wesenbergii and M. aeruginosa dominated the surface successively. M. ichthyoblabe dominated the water bottom from late spring to late autumn, while other Microcystis (including other Microcystis morphospecies and some small colonies that could not be identified) dominated the water bottom at other times. The colony size of other Microcystis showed little change during the study period and D 50 (the colony size at which 50 % of the total mass of the particles was smaller than this size) was always smaller than 100 lm. D 50 of M. ichthyoblabe was about 200 lm at most times, but reached 400 lm in early November. Colony size of M. wesenbergii and M. aeruginosa increased and then decreased, with the maximum D 50 of 700 lm and 800 lm, respectively, occurring in October. Vertical distribution of cell density and colony sizes of different Microcystis morphospecies were also comparatively analyzed, and the results suggested that the Microcystis morphospecies composition varied with depth, with large Microcystis morphospecies dominating the water surface because of their large colony size.

Interspecific variation in extracellular polysaccharide content and colony formation of Microcystis spp. cultured under different light intensities and temperatures

“…The present study and Li et al (2013b) (Li et al 2013a;Zhu et al 2015a). These findings are not paradoxical.…”

“…Above all, the largest colony induced from single cells in the laboratory is less than 200 μm in diameter (Yang and Kong 2012), but the average diameter of natural Microcystis colonies frequently exceeds 400 μm (Li et al 2013a;Zhu et al 2015a). Moreover, although all previous studies on unicellular Microcystis have used M. aeruginosa (Yang et al 2008;Li et al 2013b), the difference between laboratory-and field-grown Microcystis colonies has been clearly noted (Yang and Kong 2013;Li et al 2013b).…”

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

“…According to the long-term monitoring study of Meiliang and Gonghu Bays in Lake Taihu, a large shallow lake (Zhu et al, 2015), reported that during the water blooms season (October to December), Microcystis colonies are 300-400 µm wide in Lake Taihu (Zhu et al, 2016). The critical turbulent kinetic energy of 400 µm colony is 55.5 cm 2 s -2 , it means that under this condition, most of the colonies will sink and the water blooms will disappear.…”

Colony formation in the cyanobacterium Microcystis

“…The common morphospecies also vary significantly in colony size. M. ichthyoblabe colonies have a D 50 (50% of the population is smaller than this size) of 100–300 µm; and M. wesenbergii and M. aeruginosa were found to have a D 50 of 300–700 µm (Li et al, ; Zhu et al, ). M. aeruginosa and M. wesenbergii colonies can reach over 1000 µm in diameter (Li et al, , ).…”

“…In the early bloom period, M. ichthyoblabe dominates with small colonies (<100 µm); subsequently, M. wesenbergii and M. aeruginosa predominate with colonies of an average diameter of 400 µm. The two latter morphospecies are present until autumn (Li et al, ; Zhu et al, ).…”