Photosynthate partitioning in cultured marine phytoplankton: metabolic patterns in a marine diatom under constant and variable light intensities

Abstract

Exponential phase cultures of the marine diatom Chaetoceros simplex (clone Bbsm) were cultured at 20 degree C and 636 mu E m super(-2) s super(-1) to determine the rates at which photosynthesis and partitioning of carbon were altered in response to short-term fluctuations in light intensity. Carbon-specific uptake rates equalled cell specific growth rates for a minimum of 3 h at high light intensity (636 mu E m super(-2) s super(-1)). Low molecular weight (LMW) compounds were linearly labelled for up to 4 h under constant high light and accounted for nearly 70% of total super(14)C fixed. Under low light intensity (30 mu E m super(-2) s super(-1)), the proportion of super(14)C decreased in the LMW, chloroform-soluble and TCA-soluble fractions, but increased in particulate materials relative to that occurring at high light.