Effects of zooplankton grazing on colony formation in algae: A review
浮游动物诱发藻类群体的形成

In order to understand the mechanisms of bloom formation in cyanobacteria (blue-green algae), we reviewed the literature on inducing effects of grazing pressure of zooplankton on colony formation in algae. These published studies demonstrated that effect of colony-inducing compounds released by herbivorous zooplankton is a key factor in colony formation of algae. The inducing chemicals are not the functional constituents of the organisms involved but the result of the interaction between species. Probably two different mechanisms are involved in the colony formation. One mechanism such as in Scenedesmus spp., is that colonies are formed when daughter cells of a recently divided cell fail to separate during reproduction, the other is that colonies are formed through adhesion of already existing single cells, such as in Microcystis aeruginosa. Because a high proportion of colonies could significantly reduce the grazing rate of zooplankton, algal colony formation may be interpreted as an induced defense strategy against grazing to pare down mortality due to animal grazing. If colony formation in cyanobacteria is induced by the grazing pressure in eutrophic waters then visible blooms will occur when colonies accumulate to certain magnitudes under favorable hydrometeorological conditions. It is therefore important to conduct research on the early stage of colony formation in cyanobacteria induced by grazing pressure of herbivorous zooplankton to understand the bloom formation and to provide insights into the adaptive mechanisms of inducing defense against grazing in algae as one of the complex interactions among organisms in aquatic ecosystems.