ABUNDANCE, SIZE DISTRIBUTION AND BACTERIAL-COLONIZATION OF TRANSPARENT EXOPOLYMERIC PARTICLES (TEP) DURING SPRING IN THE KATTEGAT

The abundance, size distribution and bacterial colonization of transpa rent exopolymeric particles (TEP) were monitored in the Kattegat (Denm ark) at weekly intervals throughout the spring (February-May) encompas sing the spring diatom bloom. These recently discovered particles are believed to be formed from colloidal organic material exuded by phytop lankton and bacteria, and may have significant implications for pelagi c flux processes. During this study, the number concentration of TEP ( >1 mu m) ranged from 3 x 10(3) to 6 x 10(4) ml(-1) and the volume conc entration between 0.3 and 9.0 p.p.m.; they were most abundant in the s urface waters subsequent to the spring phytoplankton bloom. The range of TEP (encased) volume concentration was similar to that of the phyto plankton, although at times TEP volume concentration exceeded that of the phytoplankton by two orders of magnitude. The TEP size distributio n followed a power law, with the abundance of particles scaling with p article diameter((B+1)). The seasonal average estimate of beta (2.3) w as not significantly different from three, consistent with TEP being f ormed by shear coagulation from smaller particles. However, date-speci fic estimates of beta differed significantly from three, probably beca use TEP are fractal. All TEP were colonized by bacteria, and bacteria were both attached to the surface of and embedded in TEP. Yet the numb er of attached bacteria per TEP was related neither to the surface are a nor the volume, but rather scaled with TEP size raised to an exponen t of similar to 1.5. We argue that this is consistent with TEP being f ractal. Between 0.5 and 20% of the total bacterial population were att ached to TEP. Crude estimates of TEP carbon concentrations combined wi th considerations of turnover times suggest that TEP and their colloid al precursors may represent a hitherto understudied but potentially si gnificant pathway for dissolved organic carbon in the ocean.