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.