SINKING PARTICLE FLUXES FROM THE EUPHOTIC ZONE OVER THE CONTINENTAL-SLOPE OF AN EASTERN BOUNDARY CURRENT REGION

We analyze data from sediment traps and current meters moored at two l ocations 100 km apart over the Vancouver Island continental slope duri ng the spring and summer of 1990. Time-series of sinking particle flux es, major biogenic components (biogenic silica, calcium carbonate, and particulate organic carbon and nitrogen), and stable isotopic composi tion (delta(13)C(organic) and delta(15)N(total)) were determined on sa mples obtained with sequential sediment traps moored at 200-250 m dept h. Associated water property data were obtained from CTD/Rosette profi les taken during trap service periods and from current meters position ed in the surface layer and near the sediment trap. These data indicat e that the two locations (a southern site J and a northern site NJ) we re hydrographically distinct during the investigation. At site J, we f ound evidence for frequent upwelling events and more variability in th e upper layer water properties. The main difference in the sinking flu xes of particles between the two sites was the occurrence of a one-wee k event at the end of May at J that contributed about one third of the total particle flux during the sampling period. Otherwise, the total flux collected during the study and the flux of major biogenic particl es were similar at both sites. Silica shells dominated the flux of par ticles, particularly during the spring and early summer period At both sites, particulate organic carbon rather than calcium carbonate was t he main contributor to particulate carbon fluxes. The delta(13)C(organ ic) showed marked variations during the sampling period at both sites likely due to variations in the growth rate of phytoplankton and in sp ecies composition. In comparison, variations in nitrate availability a ppear to dominate the changes in delta(15)N(total).