Chlorophyll Turnover in Skeletonema costatum, a Marine Plankton Diatom

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Abstract
[3H]- and .delta.-[14C]aminolevulinic acids were incorporated into the chlorophylls of S. costatum, a marine plankton diatom. In the stationary phase of growth, the tetrapyrrole-based pigments reached steady-state labeling after 10 h. Under conditions of exponential cell division and chlorophyll accumulation, 3H was rapidly lost from the labeled chlorophylls and was replaced with 14C derived from .delta.-[4-14C]aminolevulinic acid. The kinetics of isotope dilution suggests recycling of tetrapyrrole precursors and/or 2 pigment pools, containing both chlorophyll a and chlorophyllide c, one which turns over rapidly (10 h) and another which turns over more slowly (100 h). Calculation of turnover times varied from 3-10 h for chlorophyll a and from 7-26 h for chlorophyllide c. The data suggest the dynamics of chlorophyll metabolism in S. costatum and explain the diatom''s ability to undergo light-shade adaptation within a generation time.