A 9-year time-series of planktonic foraminifer fluxes and environmental change in the Bering sea and the central subarctic Pacific Ocean, 1990–1999

A 9-year study of planktonic foraminifer fluxes was conducted in the Bering Sea (Station AB) and in the central subarctic Pacific (Station SA). Results clearly reflected variations of the water mass characteristics in the upper layers. The 9-year means of total foraminifer fluxes were the same (1400 shells m⁻² d⁻¹) at both stations. However, total foraminifer flux at Station AB tended to show its primary maximum during fall (October–December) and its secondary maximum in spring (April–June), whereas the primary maximum appeared in spring and the secondary maximum in fall at Station SA. Seasonal variation was more apparent at hemipelagic Station AB than at pelagic Station SA. Planktonic foraminifers found at both stations were of six species: Neogloboquadrina pachyderma, Globigerina umbilicata, Globigerinita glutinata, Globigerina quinqueloba, Globorotalia wilesi, and Orbulina universa. The foraminifer assemblages at the two stations reflected the temperature difference in the surface waters. The variable %G. umbilicata tended to be high in the warm surface waters during the summers. The temporal and geographical variation of %G. quinqueloba indicated that this taxon prefers regions with relatively low diatom fluxes. A notable appearance of O. universa occurred in 1997 at Station SA. During this period, other measured biogenic particle fluxes, such as those of diatoms, were low. This unusual 1997 event may be a reflection of global climatic change that happened to be observed in the central subarctic Pacific Ocean.