Abstract
A rapid method for measuring, simultaneously, the asexual reproduction rates of hundreds of phytoplankton cultures is described. This method is based on the dairy measurement of in vivo chlorophyll fluorescence read directly in the culture tubes. Hundreds of these culture tubes, containing specially prepared culture medium, can be maintained in identical environments in specially designed constant environment devices. The method is capable of measuring the acclimated reproduction rates of phytoplankton cultures with an error of 3–4% (coefficient of variation). Complete acclimation, crucial to the detection of small genetic differences between clones, takes one to three weeks, thus necessitating long-term experiments. Studies using the methods described indicate that, in a constant environment, coccolithophores and dinoflagellates reproduce at constant rates, but diatoms do not.