Extracellular carbohydrates released by the marine diatoms Cylindrotheca closterium, Skeletonema costatum and Thalassiosira pseudonana: effect of P-depletion and growth status

A laboratory study was performed on the extracellular production of carbohydrates by the marine diatoms Cylindrotheca closterium, Thalassiosira pseudonana and Skeletonema costatum. The investigation was aimed at elucidating the role of Pstarvation and growth status on abundance and chemical characteristics of the released non-attached polysaccharides. Inorganic phosphorus depletion determined an increase of total polysaccharides in all species examined compared to nutrient-replete (complete f/2) conditions. The highest abundance of polysaccharides per unit cell was found in T. pseudonana (28.4 Amol C 106 cells), followed by C. closterium (2.56 Amol C 106 cells) and S. costatum (1.18 Amol C 106 cells). Maximum production rates were found at the transition between exponential and stationary growth phase.