Importance of large colony formation in bloom-forming cyanobacteria to dominate in eutrophic ponds

Abstract

-The distribution of bloom-forming cyanobacteria in eutrophic to hypereutrophic ponds was studied in northern Taiwan in 2009. Eighty-four ponds were sampled in mid-summer, and the relationship between colony size and relative abundance of each cyanobacterial species was analyzed. Anabaena crassa and Cylindrospermopsis raciborskii were the dominant species in terms of frequency of appearance. The colony size of An. crassa increased significantly with its relative abundance. The relative abundance of C. raciborskii was usually below 10%, and its filament length was not correlated with its relative abundance. The colonies of Microcystis aeruginosa normally consisted of several tens of cells. However, when M. aeruginosa exclusively dominated the plankton community, the average number of cells in a colony reached several hundreds. The mean filament length of Planktothricoides raciborskii significantly increased with its relative abundance. The correlations between colony size and relative abundance of the ten cyanobacterial species were significantly positive for three species, insignificantly positive for five species and insignificantly negative for two species. Given the various ecological advantages of large colonies, the results of this study may suggest that the formation of large colonies of some cyanobacterial species is important to their dominance and/or bloom formation.

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

“…Nakamura et al (1993) calculated the floating velocity of Microcystis colonies and found that it was 30 and 300 lmÁs -1 for colonies of 100 and 400 lm, respectively. Thus it can be concluded that large colonies are capable of resisting disturbance of windinduced waves and float to the surface, which has been supported by previously conducted field studies (Wu and Kong 2009;Yamamoto et al 2011). In lakes and reservoirs, the disturbance caused by wind-induced waves promotes uniform distribution of particles (Wu et al 2013).…”

“…Large colony formation has been reported to be important to bloom formation (Yamamoto et al 2011), possibly because large colonies have the benefits of faster floating and settling velocities (Nakamura et al 1993;Wu and Kong 2009) when the specific gravity of different sized colonies is similar. Thus, large colonies can float up to the water surface and then form a bloom, but small colonies cannot resist disturbance by wind-induced waves, resulting in their uniform vertical distribution.…”

Green algal over cyanobacterial dominance promoted with nitrogen and phosphorus additions in a mesocosm study at Lake Taihu, China

“…4 Variations of cyanobacteria (a1, b1, c1) and green algae (a2, b2, c2) proportion (bio volume) in buckets added N (a), P (b), and N plus P (c). Controls were the same in all treatments Scheffer et al 1997;Wu and Kong 2009;Yamamoto et al 2011). Large colonial algae also favor buoyancy and stimulate the development of beneficial bacterial associations (Munoz and Guieysse 2006;Reynolds et al 1987).…”

“…Colonial or filamentous cyanobacterial dominance in eutrophic lakes may be attributed to their lower loss rate relative to other phytoplankton groups (Agusti et al 1990; Knoechel and Kalff 1975). Large colonial cyanobacteria with sheaths and mucilage can prevent cells being grazed by zooplankton grazing, viral or bacterial attack, desiccation, and other potential negative environmental factors, which play an important role in the competitive advantage over other phytoplankton taxa (Cyr and Curtis 1999;Kearns and Hunter 2001;Wu and Kong 2009;Yamamoto et al 2011).…”

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). …”