Development of particulate and dissolved carbohydrates in parallel enclosure experiments with monocultures of Thalassiosira rotula
Marine Ecology Progress Series
Three large outdoor tanks (3 to 4 m3, 4 to 5 m deep) were filled with filtered North Sea water (0.2 pm plate filters) and ~noculated with monocultures of Thalassiosira rotula. Under nearly natural conditions the diatoms showed partial good synchronization of cell division dunng 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 shcate and nitrogencontaining
... gencontaining 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 pm01 Glc Eq (glucose equivalents) dm and 18 pm01 Glc Eq dm-= respectively, indicating that a relatively large portion of synthesized carbohydrates was released by the diatoms. For synthesis and release a daynight rhythm was found with maximum increase rates during daylight. Carbohydrates were exuded intermittently and in the main by healthy cells. Maximum rates of 2.6 pm01 Glc Eq dm-3 h -' were measured, corresponding to 1.3 pm01 Glc Eq cell-' h -' . The carbohydrates were taken up as fast as they were released, probably by heterotrophic bacteria.