Finally, higher light levels and above all of increased temperature were previously thought to be responsible for the resumption of the matabolic activity of the benthic cells in spring, resulting in an active lightening of the cells allowing them to migrate back into the water column. The fact that none of these parameters influenced the recruitment of Microcystis in our study tends to negate the possibility that active processes are involved in Microcystis recruitment . On the other hand, if Microcystis benthic recruitment were a simple response to passive resuspension mechanisms, we would not have observed any differences between populations of different ages, or any recruitment without sediment mixing. Thus from this study, it appears that the recruitment process is greatly enhanced by passive resuspension of sediment, but that it also relies on an unidentified metabolic process. Microcystis benthic recruitment may, therefore, result from a combination of both active and passive processes, rather than of only one of them, as previously suggested.