The responses of benthic foraminifera to paleoceanographic changes during the last glacial maximum, deglaciation, and the Holocene in the northwestern Pacific

Abstract

Based on the changes in the species composition, abundance, and species richness of benthic foraminiferal assemblages in sediments of the northwestern Pacific, we reconstructed the paleoenvironment (paleoproductivity and near-bottom water ventilation) during the period of 8000–19000 calendar years ago (ka). A moderate seasonal productivity of the surface water, a relatively high oxygen content of the near-bottom water, and the influence of sea ice occurred during the Last Glacial Maximum in the studied area. An increased primary production and suboxic conditions in the near-bottom water were typical of the cold Heinrich 1 event (17.5–14.7 ka). A further increase in surface-water productivity and a decrease in oxygen content of the near-bottom and pore waters have been reconstructed for the second half of the Bølling/Allerød interstadial (14.7–12.8 ka) and the Pre-Boreal (11.8–9.2 ka). Surface water productivity decreased and oxygen saturation of the near-bottom water increased during the Younger Dryas (12.8–11.8 ka). In the Middle Holocene, the total decrease in productivity led to an increased oxygen content of the near-bottom and pore waters.