Extracellular release of carbon by marine phytoplankton; a physiological approach1

TLDR

Extracellular release is a normal function of healthy cells, closely linked to photosynthetic rate, and constitutes a minor component (≤5 µg C L⁻¹ h⁻¹) of coastal primary productivity, with the supply rate of carbon to the intracellular pool potentially governing its relative release rate. The production of soluble, 14 C‑labeled organic material from H¹⁴CO₃⁻ by cultures and natural populations of marine phytoplankton has been examined with particular attention to experimental technique. Time‑course studies and cell‑fractionations show that newly synthesized 14 C is distributed among cell polymers and the extracellular medium from a rapidly labeled, soluble intracellular pool, and that extracellular 14 C during transient light shock preferentially originates from rapidly mobilized polysaccharides rather than cell lysis.

Abstract

The production of soluble, 14 C‐labeled organic material from H 14 CO 3 − 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 µ g C · liter −1 h −1 ) of total primary productivity in coastal waters. Time‐course studies and chemical cell‐fractionations indicate that newly synthesized organic 14 C 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 14 C appearing during transient light shock may preferentially arise from rapidly mobilized polysaccharide and is not simply the result of cell lysis.