Fractal dimension of marine particles/aggregates is determined from light-scattering data obtained from in situ measurements in various depths ranging from 10 to 800 m. Analysis of calculated fractal dimension data indicates a correlation of fractal dimension and depth for Drake Passage. The average fractal dimension changes from 2.9 +/- 0.1 beneath the surface to 2.0 +/- 0.1 at 800 m. This agrees with a decrease of turbulent energy dissipation rate with depth, indicating domination of shear coagulation for depths </= 400 m (D = 2.7 +/- 0.3) and coagulation due to a differential sedimentation at greater depths (D = 2.1 +/- 0.3). No correlation was found between depth and fractal dimension for the Peru upwelling area. The average fractal dimension 2.8 +/- 0.3 indicates that the shear coagulation is the dominant process throughout the water column in the upwelling area. Copyright 1998 Academic Press. Copyright 1998Academic Press