Effects of planktonic copepods on transparent exopolymeric particles (TEP)abundance and size spectra

Diatoms exude considerable quantities of polymers, mainly polysaccharides, that play an important role in the process of sestonic particle aggregation in the sea. We investigated the impact of copepods on transparent exopolym eric particles (TEP) generated by the diatom Thalassiosira weissflogii. Gra zing experiments with C-14-labelled algae exudates demonstrated that copepo ds typical of the Baltic Sea were not active filtering TEP. Control experim ents showed that 'uptake' of radioactivity could be ascribed to passive upt ake, such as adsorption of radioactively-labelled particles to the body sur face. Furthermore, we tested the effect of copepods on TEP size spectra. Th e abundance and size distribution of TEP (from 1.4 to 180 mum of Equivalent Spherical Diameter) were analysed in a 4 h incubation experiment. In the p resence of copepods, the proportion of larger TEP war higher An increase in total volume of TEP in jars containing copepods (similar to2 x 10(7) mum m l(-1)) compared with control jars without copepods (similar to0.5 x 10(7) m um(3) ml(-1)) a also observed. Thee process of aggregation of TEP demonstra ted in this work, whereby copepods increase downward particle flux without consuming carbon, can have far-reaching consequences for carbon fluxes alon g the water column and for copepods feeding dynamics.