MUCOUS AGGREGATES UNDER NATURAL AND LABORATORY CONDITIONS - A REVIEW

During the years 1991 and 1999 several experiments were carried out in order to study the phenomenon of mucous aggregates in the Northern Adriatic Sea. Samples of surface and bottom sea water were treated in different ways, according to the various experiments, and then placed in 10 or 20-1 tanks. The tanks were stored in thermostatic cells at a temperature of 20 degrees C and a 16:8 h light:darkness period. After 8-10 days the formation of mucous filaments occurred. The genus Nitzschia was essential for the formation of mucous filaments, under the conditions of light and temperature applied during the experiments. Appropriate concentrations of phytoplankton and nutrients seemed to be very important also. It was possible to observe a sequence of species in the formation of mucilaginous filaments. There was a transition from species belonging to centric diatoms toward pennate diatoms. The centric diatoms (genus Chaetoceros) formed the first small aggregates which later, with the colonisation of the genus Nitzschia, developed into real filaments.