Phytoplankton extracellular production and leakage with considerations on the polysaccharide accumulation.

It is well known that many diatoms release and accumulate copious amounts of extracellular polysaccharides. Dramatic differences between diatom species exist. Examples from Prymnesiophyceae and Prasinophyceae show that algae from these classes as well may produce large amounts of extracellular polysaccharides. Soluble cell content may be released as extracellular components as a result of leaky membranes caused by unfavourable light conditions, pH, salinity, temperature, nutrient status and attack by bacteria or virus. Cellular soluble compounds may differ markedly from extracellular compounds produced under normal photosynthetic conditions. Production of polysaccharides in the Adriatic Sea may be promoted by heavy phytoplankton growth over long time under nutrient limitation. Sinking and flotation seem important processes in making aggregates and massive gels.