A comparative study of the diurnal carbon fixation patterns of nannoplankton and net plankton

Autoradiographs of nannoplankton show high photosynthetic fixation rates relative to net plankton during early daylight hours. However, net plankton contribute increasingly to community fixation during the afternoon and early evening. During darkness nannoplankton show losses of fixed 14 C greatly exceeding those from net plankton. This lack of uniformity in [ 14 C]CO 2 fixation and losses will affect the short term daylight 14 C measurements routinely used to assess long term trends in eutrophication.