An assessment of the influence of recruitment from the sediment on the development of planktonic populations of cyanobacteria in a temperate mesotrophic lake

1. A number of planktonic cyanobacteria species form resting stages that su rvive in the sediments of lakes. The significance of this life history stra tegy to the ecology of new planktonic populations was investigated in Esthw aite Water, a mesotrophic lake in the English Lake District. 2. A simple trapping technique was used to quantify vertical movements of f ive species of buoyant gas-vacuolate cyanobacteria from close to the sedime nts, along a depth transect. 3. 'Recruitment' from the sediments was found to be widespread amongst the cyanobacteria species associated with the summer phytoplankton community. 4. Estimates of the vertical upward fluxes of cyanobacteria based upon trap catches could not account for observed increases in the planktonic populat ions suggesting that 'recruitment' was not a significant source of biomass. 5. Vertical upward movements of Anabaena solitaria were recorded prior to t his species becoming established in the plankton suggesting that benthic po pulations might be a source of cells for initial pelagic growth of populati ons of this species. 6. Low numbers of vegetative filaments of Anabaena flos-aquae, Aphanizomeno n flos-aquae and Oscillatoria agardhii were observed in the plankton throug h the winter. These small overwintering populations appeared to be the prim ary source of inocula for the large summer populations of these species.