The Sea of Japan is a marginal sea, semi-enclosed by the Eurasian Continent, Korean Peninsula, Japanese archipelago, and connected to the Pacific Ocean and adjacent seas by three shallow straits (water depths < 130 m). Marginal seas are ideal natural laboratories to study biotic responses to large-scale environmental changes as they are typically sensitive to glacial-interglacial and stadial-interstadial climatic cycles. However, only limited number of studies covers time periods beyond 1 to 2 glacial-interglacial cycles. Here we present a 700,000-year record of benthic biotic response to past oceanographic changes in the southern Sea of Japan, covering the past seven glacial-interglacial cycles, based on ostracode assemblages at the IODP Site U1427. The results indicate that the long-term oxygen variability has been a major control of deep marginal sea biota. Five local extirpation events were recognized as barren zones during glacial maxima (i.e., sea-level minima) immediately before terminations I, II, IV, V, and VII in MISs 2, 6, 10, 12, and 16, which are probably caused by bottom-water oxygen depletion. The results of multivariate analyses indicated clear faunal cyclicity influenced by glacial-interglacial scale oxygen variability with the succession from opportunistic species dominance through tolerant infauna dominance to barren zone during the deoxygenation processes and the opposite succession during the recovery processes. The Sea of Japan ostracode abundance and faunal composition showed distinct difference between the post- and pre-MBE (Mid-Brunhes Event at around 400-350 ka) periods, indicating the MBE as a major disturbance event of deep-sea, especially marginal-sea ecosystems. The MBE shortened the duration of the extirpation events, fostered dominance of warmer-water species, and amplified the glacial-interglacial faunal cyclicity. Our long-term biotic response study clearly indicates that deep marginal sea ecosystems are dynamic and vulnerable to climate changes.

Supplement to: Huang, Huai-Hsuan May; Yasuhara, Moriaki; Iwatani, Hokuto; Alvarez Zarikian, Carlos A; Bassetti, Maria Angela; Sagawa, Takuya (2018): Benthic Biotic Response to Climate Changes Over the Last 700,000 Years in a Deep Marginal Sea: Impacts of Deoxygenation and the Mid‐Brunhes Event. Paleoceanography and Paleoclimatology, 33(7), 766-777