Climatic and hydrologic variability in the East China Sea during the last 7000years based on oxygen isotope records of the submarine cavernicolous micro-bivalve Carditella iejimensis

Abstract

a b s t r a c tThe micro-bivalve Carditella iejimensis inhabits the sediment surface within submarine caves at Ie Island, Okinawa, Japan. A comparison of the δ 18 O values (δ 18 O aragonite ) of empty and living shells indicates that the shell is formed over several seasons, and that the main cause of mortality is low water temperature. According to this hypothesis, it is likely that the shells with heaviest δ 18 O aragonite values (− 0.4‰) among the recent dataset formed under or close to the lower limit of growth temperature for the species. Assuming an unchanging temperature tolerance of the species during the Holocene, samples with δ 18 O aragonite values heavier than − 0.4‰ indicate unusually low temperatures and enrichment of δ 18 O of sea water (δ 18 O seawater ). The δ 18 O aragonite record of C. iejimensis from sediment cores recovered from Daidokutsu cave shows no clear long-term trend in sea surface temperature or δ 18 O seawater in the East China Sea during the past 7000 years, and indicates anomalously cool and dry events (enrichment in δ 18 O seawater ) at around 6300 and 5550 cal. years BP. These events may have been related to changes in the activity of the East Asian monsoon, related in turn to weakening solar activity. In contrast, these anomalies appear to be obscured during the last 1000 years, including a weak Asian summer monsoon event during the Little Ice Age, thereby indicating that the mode of the East China Sea climatic and hydrologic response to decadal-to centennial-scale variability in the intensity of East Asian monsoon has varied over the past 7000 years.

Possible Cavern-Forming Activity at Millennial Time Scales and its Impact on Variations in Submarine Cave Environments and Habitat Availability, Okinawa, Japan

“…years BP was related to an intensification of the winter monsoon, although they reported no changes in temperatures or salinities during the past 2700 years. Yamamoto et al (2010) Kitamura et al (2013) confirmed that no changes have occurred in either sea-surface temperatures or salinities during the past 7000 years. These results are consistent with the findings of previous studies in the East China Sea (Jian et al, 2000;Ijiri et al, 2005;Sun et al, 2005;Lin et al, 2006;Kubota et al, 2010).…”

“…1a), are among the northernmost sites at which P. taniguchii has been found. According to Yamamoto et al (2010), seasonal changes in water temperature in Daidokutsu Cave range from 29 uC in August-September to 21 uC in February. Data from the Japan Oceanographic Data Center (2007) show that, at water depths of 20 m, similar to those of the study area, water temperatures range from 28.2 6 0.6 uC in September to 22.0 6 0.9 uC in February, which indicates that P. taniguchii can survive at temperature of 21 uC during the winter season.…”

“…For example, oxygen-isotopic compositions of coralline sponges and micro-bivalves from submarine caves have been studied as proxies for palaeotemperature (Böhm et al, 2000;Haase-Schramm et al, 2003;Yamamoto et al, 2008Yamamoto et al, , 2009bYamamoto et al, , 2010Kitamura et al, 2013). In addition, the history of sea level changes has been examined using both speleothems and changes in faunal assemblages preserved in cave sediments (Dorale et al, 2010;Tuccimei et al, 2010;van Hengstum and Scott, 2011, 2012, van Hengstum et al, 2011.…”

Evidence of Recent Warming in the Okinawa Region, Subtropical Northwestern Pacific, from an Oxygen Isotope Record of a Cave-Dwelling Marine Micro-Bivalve

“…However, there are no records of Holocene SSTs for the Okinawa Islands based on coral proxies, because well preserved fossil corals (in situ occurrences and no diagenetic alternation) have not been found. Kitamura et al (2007) and Yamamoto et al (2008Yamamoto et al ( , 2010 analyzed δ 18 O values of empty (dead) whole shells (δ 18 O shell ) of the marine cave-dwelling microbivalve Carditella iejimensis ( Figure 1c) collected from cored sediments in the submarine cave Daidokutsu (meaning 'large cave' in Japanese) at 29-m water depth off Okinawa Island (26°43′N, 127°44′E) (Figure 1c, d). Carditella iejimensis shells are less than 3.5 mm in height and length, and the species inhabits the sediment surface.…”

Positive precipitation–evaporation budget from AD 460 to 1090 in the Saloum Delta (Senegal) indicated by mollusk oxygen isotopes

“…Mollusk shells have been shown to be faithful environmental archives (Goodwin et al, 2001;Carré et al, 2005;Schöne et al, 2005;Lazareth et al, 2006;Yamamoto et al, 2010;Batenburg et al, 2011;Carré et al, 2012a;Sadler et al, 2012).…”