A new method for measuring soluble cellular organic content and a membraneproperty, T-m, of planktonic algae

A new method of releasing cellular soluble organic matter from microalgae i s reported. This method, which could be used to help characterize the produ ction and taxonomic composition of a phytoplankton bloom, was developed in the laboratory to determine the transition temperature, T-m, for planktonic algae. The T-m of these algae is defined as the temperature at which half the cellular soluble carbon is found extracellularly under standard conditi ons, by analogy with the definition of T-m in bacteriology. Values of T-m i n the range of 23-46 . 5 degrees C are reported for six species of Bacillar iophyceae (diatoms) and two species of Prymnesiophyceae. Species-specific T -m values are highly reproducible and are regarded as an intrinsic property of the species and its physiological races. Possible field uses of the met hod are discussed.