Development of particulate and dissolved carbohydrates in parallel enclosure experiments with monocultures of Thalassiosira rotula

Abstract

Three large outdoor tanks (3 to 4 m super(3), 4 to 5 m deep) were filled with filtered North Sea water (0.2 mu m plate filters) and inoculated with monocultures of Thalassiosira rotula). Under nearly natural conditions the diatoms showed partial good synchronization of cell division during exponential growth. Concentrations of particulate and dissolved carbohydrates increased slowly at this time. A rapid increase was measured at the beginning of the stationary phase when silicate and nitrogen-containing nutrients in the enclosures were exhausted and proteins and amino acids were synthesized at a lower rate. Particulate and dissolved carbohydrates reached maximum values of 25 mu mol Glc Eq (glucose equivalents) dm super(-3) and 18 mu mol Glc Eq dm super(-3) respectively, indicating that a relatively large portion of synthesized carbohydrates was released by the diatoms. For synthesis and release a day-night rhythm was found with maximum increase rates during daylight.