Aggregation processes in the benthic boundary layer at the Celtic Sea continental margin

Small particle scavenging rates in the benthic boundary layer (BBL) are cal culated for the interaction between measured large particles and single par ticles at five stations (204, 667, 1445, 2285, 3660 m) at the Celtic Sea co ntinental margin. In summer particle scavenging of small particles less tha n or equal to 10 mu m at the study site takes place under typical how condi tions of u* > 0.2 cm s(-1). Scavenging of 10 mu m particles can take place only at high particle concentrations, which result from sediment erosion. I t is expected that the BBL aggregates found in the Celtic Sea at the mid- a nd lower-slope areas originate in sediment resuspension events. During thes e times of enhanced flow conditions, aggregates are formed and compacted by shear, which accounts for the fact that they do not disaggregate when they enter the viscous sublayer. Total clearance of bottom nepheloid layers occ urs only during times of transport of large aggregates > 1000 mu m after th e arrival of phytodetrital aggregates on the sea Boor with number concentra tions > 200 dm(-3) and flow conditions with u(*) > 1 cm s(-1). (C) 2000 Els evier Science Ltd. All rights reserved.