BACTERIOPLANKTON PRODUCTION DETERMINED BY DNA-SYNTHESIS, PROTEIN-SYNTHESIS, AND FREQUENCY OF DIVIDING CELLS TUAMOTU ATOLL LAGOONS AND SURROUNDING OCEAN

This study compares three independent methods used for estimating bact erioplankton production in waters from the lagoon (mesotrophic) and th e surrounding ocean (oligotrophic) of two atolls from the Tuamotu arch ipelago (French Polynesia). Thymidine and leucine incorporation were c alibrated in dilution cultures and gave consistent results when the fi rst was calibrated against cell multiplication and the second against protein synthesis. This study demonstrates that determining conversion factors strongly depends on the selected calculation method (modified derivative, integrative, and cumulative). These different estimates a re reconciled when the very low proportion of active cells is accounte d for.Frequency of dividing-divided cells (FDDC) calibrated using the same dilution cultures led to unrealistically high estimates of bacter ial production. However, highly significant correlations between FDDC and either thymidine- or leucine-specific incorporation per cell were found in lagoon waters in situ. These correlations became more positiv e when oceanic data were added. This suggests that the FDDC method is also potentially valid to determine bacterioplankton growth rates afte r cross calibration with thymidine or leucine methods. If recommended precautions are observed, the three methods tested in the present stud y would give reliable production estimates.