TY - JOUR
T1 - Intraspecific variations in carbon-isotope and oxygen-isotope compositions of a brachiopod Basiliola lucida collected off Okinawa-jima, southwestern Japan
AU - Takayanagi, Hideko
AU - Asami, Ryuji
AU - Abe, Osamu
AU - Miyajima, Toshihiro
AU - Kitagawa, Hiroyuki
AU - Sasaki, Keiichi
AU - Iryu, Yasufumi
N1 - Funding Information:
We are most grateful to K. Arai and T. Itaki (AIST/GSJ) for providing specimens of B. lucida collected during the GH09 cruise of the R/V Daini Hakurei-maru. Special thanks are due to K. Endo (Graduate School of Science, University of Tokyo) for taxonomic identification of brachiopod specimens and for providing useful information on modern brachiopods in Japan. Deep appreciation is expressed to Y. Tsuji, K. Ariyoshi, and E. Shinbo (JOGMEC/TRC) for their assistance with the δ 18 O SW measurements. This research was financially supported, in part, by a research fellowship from the Japan Society for the Promotion of Science (to H.T.), a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (21340152 to Y.I.), and the Rising Star Program for Subtropical Island Sciences, University of the Ryukyus (to R.A.). The manuscript was significantly improved by the comments and suggestions of Y. Rosenthal and two anonymous reviewers.
PY - 2013/8/5
Y1 - 2013/8/5
N2 - This study presents intraspecific variations in carbon-isotope (δ13C) and oxygen-isotope (δ18O) compositions of nine specimens of a subtropical brachiopod, Basiliola lucida, collected west of Okinawa-jima, Ryukyu Islands, southwestern Japan. The δ13C values of samples collected along the maximum growth axis (ontogenetic samples) from two modern and seven older (pre-1945 cal AD) shells show no seasonal changes. The modern shells, which were collected from comparable depths, have similar δ13C values that fall within the range of calcite precipitated in isotopic equilibrium with ambient seawater (equilibrium calcite) (δ13CEC values), and their mean δ13C values are ~1.1-1.6‰ less than those from the older shells. This decrease in δ13C values is similar in magnitude to the decreases in atmospheric CO2 and the oceanic dissolved inorganic carbon at the sea surface in recent years (13C Suess effect), suggesting that the effect can even be detected at water depths of 200-300m in the subtropical northwestern Pacific Ocean. The δ18O values fluctuate within a narrow range (0.26-0.41‰) with no seasonal changes, and they exhibit small (0.14-0.51‰) offsets from those of equilibrium calcite (δ18OEC values). A statistically significant negative linear relationship is established between seawater temperature and mean δ18O values of the nine shells, but the slope (-0.31‰/°C) is steeper than those of equilibrium calcite (-0.23‰/°C) and other calcareous organisms (-0.15‰ to ?0.26‰/°C). The cross-plots of the δ13C and δ18O values suggest that the degree of the vital effect varies among individuals in this species. The δ13C and δ18O values of B. lucida are potentially useful for reconstructing the δ13C and δ18O evolution of ancient oceans, because both values show small intraspecific variations, the former is identical to the δ13CEC values, and the latter shows small within-shell variations and small, nearly constant offsets from the δ18OEC values.
AB - This study presents intraspecific variations in carbon-isotope (δ13C) and oxygen-isotope (δ18O) compositions of nine specimens of a subtropical brachiopod, Basiliola lucida, collected west of Okinawa-jima, Ryukyu Islands, southwestern Japan. The δ13C values of samples collected along the maximum growth axis (ontogenetic samples) from two modern and seven older (pre-1945 cal AD) shells show no seasonal changes. The modern shells, which were collected from comparable depths, have similar δ13C values that fall within the range of calcite precipitated in isotopic equilibrium with ambient seawater (equilibrium calcite) (δ13CEC values), and their mean δ13C values are ~1.1-1.6‰ less than those from the older shells. This decrease in δ13C values is similar in magnitude to the decreases in atmospheric CO2 and the oceanic dissolved inorganic carbon at the sea surface in recent years (13C Suess effect), suggesting that the effect can even be detected at water depths of 200-300m in the subtropical northwestern Pacific Ocean. The δ18O values fluctuate within a narrow range (0.26-0.41‰) with no seasonal changes, and they exhibit small (0.14-0.51‰) offsets from those of equilibrium calcite (δ18OEC values). A statistically significant negative linear relationship is established between seawater temperature and mean δ18O values of the nine shells, but the slope (-0.31‰/°C) is steeper than those of equilibrium calcite (-0.23‰/°C) and other calcareous organisms (-0.15‰ to ?0.26‰/°C). The cross-plots of the δ13C and δ18O values suggest that the degree of the vital effect varies among individuals in this species. The δ13C and δ18O values of B. lucida are potentially useful for reconstructing the δ13C and δ18O evolution of ancient oceans, because both values show small intraspecific variations, the former is identical to the δ13CEC values, and the latter shows small within-shell variations and small, nearly constant offsets from the δ18OEC values.
UR - http://www.scopus.com/inward/record.url?scp=84877904240&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84877904240&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2013.03.026
DO - 10.1016/j.gca.2013.03.026
M3 - Article
AN - SCOPUS:84877904240
SN - 0016-7037
VL - 115
SP - 115
EP - 136
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
ER -