SEASONAL SIZE SPECTRA OF TRANSPARENT EXOPOLYMERIC PARTICLES (TEP) IN A COASTAL SEA AND COMPARISON WITH THOSE PREDICTED USING COAGULATION THEORY

The abundance and size distribution of transparent exopolymeric partic les (TEP) were monitored in the Kattegat (Denmark) during 1 yr. TEP nu mber concentration ranged from 0.5 x 10(5) to 3.8 x 10(5) ml(-1) and t he volume concentration between 3 and 310 ppm. TEP volume concentratio n peaked during the spring bloom and again during the summer period. T he observed accumulation of TEP during summer is consistent with the r ecent observation that dissolved organic matter (DOM) concentration ha s a similar seasonal distribution and suggests that TEP are formed fro m DOM. The supposed mode of formation of TEP (coagulation of colloidal organic particles) was tested by comparing the observed TEP size spec tra with those predicted by means of a coagulation model. The model us ed was a steady-state version of a particle coagulation model extended to include interactions between TEP and non-TEP particles. The spectr a generated by the model were fitted to the observed TEP size spectra. The spectra predicted from the model fitted the observations relative ly well, suggesting that the model provides a good description of the kinetics of TEP coagulation and that coagulation of colloids is an imp ortant mode of TEP formation. The best fits of the simulated steady-st ate TEP spectra to the observed ones were used to estimate TEP turnove r rates. Seasonal estimates of TEP turnover rates, calculated assuming a sticking coefficient of 0.6 for TEP-TEP interactions and 0.3 for in teractions between TEP and non-TEP particles, ranged between 0.1 and 0 .9 d(-1). TEP turnover rate appeared to be most sensitive to interacti ons between TEP and non-TEP particles. Relative TEP carbon fluxes were compared with historical primary production estimates and showed almo st identical seasonal patterns. According to TEP concentration, turnov er times and estimates of carbon content, TEP carbon accumulation may represent an important fraction of the primary production and, thus, T EP and their colloidal precursors may represent a significant pathway for dissolved organic carbon in the ocean.