Effects of Light and Wind Speed on the Vertical Distribution of Microcystis aeruginosa Colonies of Different Sizes during a Summer Bloom

Abstract

Different dynamics, of the vertical distribution of Microcystis aeruginosa colonies of different sizes, were examined in a large shallow lake (Taihu Lake) during a summer bloom. During the observation the Microcystis colonies, larger than 120 μm, were mainly concentrated in the upper layer both under calm and windy conditions. Colonies from 36 μm to 120 μm showed a clear relationship to wind conditions whereas colonies less than 36 μm showed a nearly uniform vertical distribution at the different depths. There was no clear relationship between the vertical distribution of colonies larger than 36 μm and light intensity. However, at solar noon, colonies less than 36 μm were mainly distributed in the middle layers of the water column. The results indicate that small colonies are easily affected by the wind-induced mixing, and they show an ability for active movement in response to light intensity under calm conditions. In contrast, large colonies tend to show little diurnal repositioning to light intensity and thereby are mainly concentrated in the surface layer.

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

“…Water blooms can be effectively predicted in numerical models that simulate the occurrence and disappearance of water blooms. The cyclic appearance and disappearance of water blooms is mainly driven by the spatial aggregation and dispersion of Microcystis by wind waves (Wu and Kong, 2009;Zhu et al, 2014). Consequently, this process is assumed in numerical simulations of blooms.…”

“…In a laboratory study, Nakamura et al (1993) found that the measured floating velocity of Microcystis is proportional to colony size. Wu and Kong (2009) investigated Microcystis blooms in Lake Taihu, a large freshwater lake in the Yangtze Delta of Jiangsu Province, China. They found that large Microcystis colonies (>120 µm) can overcome wind-wave disturbance and thus accumulate at the water surface, whereas small colonies (<36 µm) tend to mix with the turbulence.…”

Cyanobacterial Toxins of the Laurentian Great Lakes, their Toxicological Effects, and Numerical Limits in Drinking Water

“…In some cases, these colonies may coalesce into free-floating mats or "scums" on the surface of the lake with a bright blue or bluegreen appearance due to the presence of C-phycocyanin, their major light harvesting pigment ( Figure 1). Colony size affects cyanobacterial vertical movement, and aids in diffusion of nutrients and signaling molecules between cells [68,69]. Large colony size resists predation by zooplankton (unlike other non-colonial algae) and filter feeding organisms including Dreissenids (e.g.…”

Using a laser particle analyzer to demonstrate relationships between wind strength andMicrocystiscolony size distribution in Lake Taihu, China

“…Large colony formation plays an important role in the occurrence of Microcystis blooms (Yamamoto et al 2011) because large colonies have higher speeds of vertical migration than smaller ones (Nakamura et al 1993) and this leads to accumulation near the water surface, thereby forming blooms (Wu & Kong 2009). …”