Abstract

Seasonal and interannual changes in the flux of planktic foraminifers were studied in the Humboldt Current System off Coquimbo, Chile (30°S; 73°15?W), using material collected by time series sediment traps located at 2300 m water depth and 100 nautical miles from the coast. The almost continuous record spans 6 years (1993-1998) with a temporal resolution of 6-13 days. The seasonal flux pattern of planktic foraminifers was marked by high fluxes during austral late winter-early summer (August-January) and low fluxes during the fall-early winter period (March-July). Five species contributed ?90% of the total flux of planktic foraminifers: Globigerina bulloides, Neogloboquadrina incompta, N. pachyderma, N. dutertrei, and Globigerinella calida. Stable oxygen isotope variability in foraminifer shells appears to be driven by seasonal changes in surface seawater temperature; isotope data of G. bulloides and N. incompta (>212 and 150-212 ?m size classes) suggest that water-column stratification dominates during the low-flux period and mixing during the high-flux period. The strong 1997-1998 El Niño event had only a limited impact on the planktic foraminifer flux. The most significant El Niño-related signal was a remarkable increase in the flux and abundance of species that, under normal conditions, only accounted for <10% of the total planktic foraminiferal assemblage. © 2004 Elsevier Ltd. All rights reserved.