Seasonal flux patterns of planktic foraminifera in the Peru–Chile current

Seasonal changes in the flux of planktic foraminifera were studied in the highly productive Peru–Chile Current (30°S; 73°10′W), using material collected by time series sediment traps 100 nm off the Chilean coast near Coquimbo. Field work was carried out during the El Niño event of 1991/1992 (6 months) and under normal conditions in 1993/1994 (1 year). The seasonal cycle 1993/1994 was marked by high fluxes of planktic foraminifera between August and January (southern winter to summer) and low fluxes during the rest of the year (southern summer to winter). High foraminifera fluxes coincided with increased coastal upwelling, as indicated by stable oxygen isotope data of the planktic foraminifera species Globigerina bulloides and Neogloboquadrina pachyderma (dex.). The isotope data also point to a stratified water column without upwelling in early 1994 concomitant with low fluxes of foraminifera. Variations of the faunal composition were mainly due to specific hydrographic conditions such as severe upwelling events or passing oceanographic fronts. During the El Niño event of 1991/1992, foraminiferal fluxes were only slightly lower, and the faunal composition reflected the somewhat warmer sea surface temperatures under condition. However, there were only small differences between the flux pattern of 1991/1992 and 1993/1994. The foraminiferal fluxes in the Peru–Chile Current are among the highest of the main upwelling areas in the Eastern Pacific. Interestingly, even during El Niño conditions, the Peru–Chile Current is characterized by a high production of foraminifera.