Dynamik der Feinfraktion im Oberflächenhorizont permeabler Schelfsedimente.

This thesis presents new findings on the dynamics of fine-grained organic material in permeable shelf sediments, founded on in situ experiments and a one-year field study in an intertidal sandflat. The main results of these investigations are:. In shallow shelf regions, advective exchange of solutes and particles between the bottom water and permeable sandy sediments can be a fast and efficient transport process. Within 13 h, tracer particles (1-30 µm) were carried ca. 5 cm into coarse-grained (500-1000 µm) sediment. The net rate of bottom water "filtration" by this sediment averaged 14 l m-2 hol-1. The depth distributions of natural and artificial partieles depended on sediment permeability and particle size. Thus, the corresponding results of earlier laboratory studies are confirmed in a natural marine environment. The depth distributions of fine-grained ( < 70 µm) material and pore water characteristics in natural sandy sediment indicated hydrodynamic influence down to 4-8 cm below the sediment surface. Worst case estimates of biodiffusion coefficients at the sudy site imply only minor macrofaunal contribution to particle transport.