Sinking particle fluxes from the euphotic zone over the continental slope of an eastern boundary current region

Authors: M.A. Pena; K.L. Denman; J.R. Forbes; S.E. Calvert; R.E. Thomson

Source: Journal of Marine Research, Volume 54, Number 6, 1 November 1996 , pp. 1097-1122(26)

Publisher: Sears Foundation for Marine Research

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Abstract:

We analyze data from sediment traps and current meters moored at two locations 100 km apart over the Vancouver Island continental slope during the spring and summer of 1990. Time-series of sinking particle fluxes, major biogenic components (biogenic silica, calcium carbonate, and particulate organic carbon and nitrogen), and stable isotopic composition ( dgr

¹³C_organic and dgr

¹⁵N_total) were determined on samples obtained with sequential sediment traps moored at 200–250 m depth. Associated water property data were obtained from CTD/Rosette profiles taken during trap service periods and from current meters positioned in the surface layer and near the sediment trap. These data indicate that the two locations (a southern site J and a northern site NJ) were hydrographically distinct during the investigation. At site J, we found evidence for frequent upwelling events and more variability in the upper layer water properties. The main difference in the sinking fluxes of particles between the two sites was the occurrence of a one-week 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 particles were similar at both sites. Silica shells dominated the flux of particles, particularly during the spring and early summer period. At both sites, particulate organic carbon rather than calcium carbonate was the main contributor to particulate carbon fluxes. The dgr

¹³C_organic showed marked variations during the sampling period at both sites likely due to variations in the growth rate of phytoplankton and in species composition. In comparison, variations in nitrate availability appear to dominate the changes in dgr