Algal sedimentation: the cause of a diatom — blue-green succession

SummaryThe in situ carbon fixation of individual phytoplankton species in a small Quebec lake was quantitatively determined through the application of track autoradiography. The results enabled the calculation of daily growth rates of the individual species. The decline of the summer diatom population (Tabellaria fenestrata) appears to be the result of a high sinking rate rather than a low production rate. In contrast the blue-green algal population (Anabaena planctonica) continues to increase despite a lower growth rate, and becomes dominant in the community, apparently due to a lower sinking rate.