AGGREGATION OF A DIATOM BLOOM IN A MESOCOSM - THE ROLE OF TRANSPARENTEXOPOLYMER PARTICLES (TEP)

The role of TEP (Transparent Exopolymer Particles) in the flocculation of a diatom bloom was studied under controlled conditions in a mesoco sm. The concentration of TEP increased exponentially during growth, fl occulation and senescence of the bloom. Aggregation began dominating t he particle dynamics of TEP during the early growth phase of the bloom , several days prior to the appearance of large flocs and nutrient dep letion. TEP aggregated with themselves and with phytoplankton due to t he high stickiness of TEP, but phytoplankton was not observed to aggre grate with itself. The production of TEP, estimated from changes in co ncentration, did not increase after nutrients were depleted. The conce ntration of TEP was a linear function of chl alpha and particulate org anic carbon (POC), indicating that production of TEP was linked to gro wth rather than standing stocks of phytoplankton. The ratio between TE P and phytoplankton appeared to be one of the factors determining the onset of the flocculation of the bloom. The concentration of TEP may h ave been decreased by bacterial degradation. Bacterial degradation of TEP may explain the low TEP to chl alpha values, the decrease in stick iness of particles as the bloom progressed, and the retarded onset of flocculation.