Extracellular release of carbon by marine phytoplankton; a physiological approach1

Abstract

The production of soluble, 14C‐labeled organic material from H14CO3− by cultures and natural populations of marine phytoplankton has been examined with particular attention to experimental technique. Extracellular release is a normal function of healthy cells, is closely related to photosynthetic rate, and is a minor component (up to 5 µg C · liter−1 h−1) of total primary productivity in coastal waters. Time‐course studies and chemical cell‐fractionations indicate that newly synthesized organic 14C is distributed among various cell polymers and the extracellular medium from a rapidly labeled, soluble intracellular pool of small molecules. The rate of supply of carbon to this pool may determine the relative rate of release. Extracellular 14C appearing during transient light shock may preferentially arise from rapidly mobilized polysaccharide and is not simply the result of cell lysis.