Productivity changes in the Bering Sea during the late Quaternary

Changes in biological productivity of the Bering Sea have been evaluated for the late Quaternary based on biogenic opal, calcium carbonate, and microfossils in two piston cores. Biological productivity increased during Marine Isotope Stage (MIS) 1 after the last glaciation. During the last deglaciation, two pronounced peaks of calcium carbonate content were observed at ca. 2400 m water depth, which can be explained by the “CaCO3 compensation hypothesis” and coccolithophore blooms. Simultaneous with the CaCO3 peaks, oxygen-poor deep water was apparently distributed in the Aleutian Basin based on benthic foraminiferal assemblages. The low-O2 events seem to be related to deep-water circulation and/or elevated productivity in the northwest Pacific. After the CaCO3 peak events, biogenic opal contents and diatoms increased gradually, associated with enhanced vertical mixing with an inflow of the Alaskan Stream through the eastern Aleutian Arc passes.