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1 April 2021 Carbon and Oxygen Isotope Records of Tridacna squamosa Shells from two Different Latitudes in the Ryukyu Islands
Satoshi Kodama, Hideko Takayanagi, Kosuke Yoshii, Thuy Thi Nhu Ha, Ryuji Asami, Osamu Abe, Yasufumi Iryu
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Abstract

We report carbon (δ13C) and oxygen (δ18O) isotope records of two modern giant clam (Tridacna squamosa) shells from two sites (Ishigaki-jima and Okinoerabu-jima) at different latitudes in the Ryukyu Islands, Japan. The δ13C profiles of samples from the inner shell layer on cross-sections along the maximum growth axis display no ontogenetic trends or seasonal variations. This finding suggests that the calcification site is likely to be unaffected by CO2 uptake and release resulting from the metabolic activity of the molluscan host and algal symbionts. The δ18O profiles show distinct seasonal cycles. After accounting for the influence of seawater δ18O, the time-series variations are consistent with variations in sea surface temperature, and the temperature dependency of oxygen isotope fractionation is nearly identical to previously published δ18O–temperature relationships for biogenic and synthetic aragonite. We conclude that δ18O records from pristine fossils of this species will enable accurate paleoenvironmental reconstructions at high temporal resolution.

© by the Palaeontological Society of Japan
Satoshi Kodama, Hideko Takayanagi, Kosuke Yoshii, Thuy Thi Nhu Ha, Ryuji Asami, Osamu Abe, and Yasufumi Iryu "Carbon and Oxygen Isotope Records of Tridacna squamosa Shells from two Different Latitudes in the Ryukyu Islands," Paleontological Research 25(2), 79-92, (1 April 2021). https://doi.org/10.2517/2020PR003
Received: 9 April 2019; Accepted: 21 February 2020; Published: 1 April 2021
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KEYWORDS
carbon isotope
isotopic equilibrium
oxygen isotope
Ryukyu Islands
Tridacna squamosa
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