Attenuation of light influences the size of Microcystis colonies

Colony formation provides excellent advantages for the dominance of Microcystis. However, studies on micro-environments during the process of colony formation are rare, especially regarding intra-colony light usage. This study analyzed the attenuation of light intensity in Microcystis colonies, where most objects followed Lambert- Beer law (I = I-0 10(-1256x10-3bc)). Intra-colony light limited the maximum thickness of the colony (B-Max = 4.3 x 10(5) c(-1)) and thus affected colony size. Field data showed that the colony size for M. ichthyoblabe was small and limited to approximately 300 mu m, while larger colonies were mainly formed by M. aeruginosa and M. wesenbergii respectively. These results imply that the strategies used by morphospecies to allow colonies to tolerate intra-colony light limitation might be different; M. aeruginosa benefited from a reticular growth pattern, and M. wesenbergii colonies were large (500 mu m), obtaining a large thickness by lowering cell concentration. The results obtained in this work suggest that M. aeruginosa and M. wesenbergii had more advantages regarding intra-colony light usage, colony size level and bloom formation ability in summer and autumn.