GROWTH AND OSMOREGULATION OF CHAETOCEROS-MUELLERI IN RELATION TO SALINITY

The growth and osmoregulation of Chaetoceros muelleri Lemmermann (Baci llariophyceae) were investigated as a function of salinity. This centr ic diatom grew well over a wide range of salinity and required concent rations of NaCl above 10 mM for growth. Using gas chromatography-mass spectroscopy (GC-MS) analysis of cell extracts, we demonstrated that t he alga contains an isomer of cyclohexanetetrol. The level of this iso mer increased with increasing salinity. Levels of free amino acids als o increased with increasing salinity, and quantitative determination w ith an amino acid analyzer revealed that the level of glutamic acid in creased the most with increases in salinity. Levels of intracellular K + and Cl- also increased significantly with increases in salinity. Thu s, in C. muelleri, not only organic solutes such as the cyclohexanetet rol isomer and glutamic acid, but also inorganic solutes such as K+ an d Cl- contribute to osmoregulation.