Note on the variability of heterotrophic activity measurements by the 14C method in sea water

Twenty five measurements in triplicate of heterotrophic activity in sea water showed good reproducibility. The mean coefficient of variation was 6.2%, which is lower than the coefficient of variation obtained with a similar method for primary production measurements. This result indirectly confirms that most heterotrophic activity can be attributed to a great number of small cells, i.e., bacteria which, if not free-swimming, are fixed to particles of smaller size than the average phytoplankton. The good reproducibility obtained also suggests that there was no extraneous contamination despite non-sterile working conditions.