Holocene shell geochemical and paleoecological records of a submarine cave in Okinawa, Japan

Abstract

Submarine cave is a cryptic system that was believed to be immune to external climate change. However, our study in a submarine cave in Okinawa has found that the benthic cave ecosystem could be affected by intensified East Asian Winter Monsoon, based on the synchronicity of species diversity of ostracods, foraminifers and bivalves and the paleoclimatic record outside the cave. To further investigate the relationship between cave ecosystem responses to climate change, here we use in situ ostracod (genus: Loxoconcha) shell isotopic ratios such as Sr/Ca and Mg/Ca to reconstruct the past climate (e.g. temperature, salinity) of the submarine cave Daidokutsu, and compare the geochemical records with paleoecological records of Okinawa Daidokutsu Cave in the past 7000 years. We will also present our inter-model comparison between different paleoclimate proxies (e.g. δ18O of bivalves) used in the study of Daidokutsu Cave, so as to identify suitable proxies for benthic environmental reconstruction.