Deep-sea biotic response to oxygen variability and Pleistocene global changes: paleoecological and macroevolutionary dynamics in a marginal sea

Abstract

The Sea of Japan is a marginal sea, connecting to adjacent seas by four shallow straits (water depths <130 m). Marginal seas are ideal for studying biotic responses to large-scale environmental changes as they often are sensitive to glacial-interglacial and stadial-interstadial climatic cycles as well as longer scale changes. However, only a limited number of studies cover time periods beyond the last two glacial-interglacial cycles. Here we present a two million year record of benthic biotic response to paleoceanographic changes in the southern Sea of Japan, based on ostracode assemblages at the Integrated Ocean Drilling Program (IODP) Site U1426 and U1427. Results show that (1) orbital-scale faunal variability have been influenced by eustatic sea level fluctuations and oxygen variability, and (2) faunal composition showed distinct difference between the post-MBE and pre-MBE (Mid-Brunhes Event) periods. Long-term oxygen variability in the bottom water has been the major control impacting the marginal-sea biota. The MBE was a major disturbance event in deep-sea ecosystems, as several studies have recently reported major faunal events during the Mid-Pleistocene in various oceans and seas. Benthic ecosystems in marginal seas are sensitive and vulnerable to both short-term and long-term climatic changes.