TY - JOUR
T1 - Quantitative analysis of intraspecific variations in the carbon and oxygen isotope compositions of the modern cool-temperate brachiopod Terebratulina crossei
AU - Takayanagi, Hideko
AU - Asami, Ryuji
AU - Otake, Tsuguo
AU - Abe, Osamu
AU - Miyajima, Toshihiro
AU - Kitagawa, Hiroyuki
AU - Iryu, Yasufumi
N1 - Funding Information:
We are most grateful to K. Yamamoto for providing samples of T. crossei and seawater from Otsuchi Bay, and for his continuous encouragement. We gratefully acknowledge M. Kurosawa, K. Morita, and M. Hirano for their assistance with field works, and M. Takagi and Y. Yokosawa for providing oceanographic records for Otsuchi Bay. We also thank K. Endo and M. Saito for their useful information on the modern brachiopods from Otsuchi Bay. Deep appreciation is expressed to Y. Tsuji and E. Shimbo for their assistance with the stable isotope measurements. We also thank J. Nemoto for taking photographs. This research was financially supported, in part, by a research fellowship from the Japan Society for the Promotion of Science (to H.T.) and a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science ( 21340152 and 26302008 to Y.I.). We would like to express our condolences to the people of Otsuchi, who suffered from the catastrophic effects of the earthquake and its associated tsunami on 11 March 2011. The manuscript was significantly improved by the comments and suggestions of Y. Rosenthal and two anonymous reviewers.
Publisher Copyright:
© 2015 Elsevier Ltd.
Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2015/12/1
Y1 - 2015/12/1
N2 - This study unravels intraspecific variations in the carbon isotope (δ13C) and oxygen isotope (δ18O) compositions of shells of the modern cool-temperate brachiopod Terebratulina crossei collected at a water depth of 70m in Otsuchi Bay, northeastern Honshu, Japan. Brachiopod shells have been used as proxies of the δ13C values of dissolved inorganic carbon (DIC) (δ13CDIC) and seawater temperature/δ18O (δ18OSW) values to reconstruct the evolution of Phanerozoic oceans. To identify more reliable shell portions as the proxies, we conducted a rigorous time-series comparison of δ13C and δ18O values between the brachiopod shells and calcite precipitated in isotopic equilibrium with ambient seawater (equilibrium calcite) (δ13CEC and δ18OEC values, respectively). Samples were collected from the outer and inner surfaces of the secondary shell layer along the maximum growth axis (ontogenetic-series and inner-series samples, respectively). The ontogenetic-series δ13C values, which showed regular annual and irregular non-annual cycles, partly fell in but were mostly less than the range of the δ13CEC values. The δ13C cycles were often associated with one or two minor negative peaks. The peaks were likely resulted from an increased incorporation of respiration-derived 12C due to elevated metabolic activity during spawning. The ontogenetic-series δ18O values showed distinct seasonal variations and were mostly within the range of δ18OEC values. The amplitude of the δ18O profiles was relatively large during the younger fast-growth stage, and decreased during the senescent slow-growth stage. The inner-series δ13C and δ18O values of individual shells varied within narrow ranges. The inner-series δ13C values were close to the minimum δ13CEC values. The inner-series δ18O values were in the upper range of the δ18OEC values. Kinetic isotope fractionation effects were evident, but its degree varied among different shells. We identified the shell portions reliably recording past ocean environments. The best estimates of annual average δ13CDIC values were obtained from ontogenetic-series δ13C values near the anterior shell edge and from inner-series δ13C values; those of the annual average seawater temperature were obtained from ontogenetic-series δ18O values from the entire transect and from the fast-growth stage.
AB - This study unravels intraspecific variations in the carbon isotope (δ13C) and oxygen isotope (δ18O) compositions of shells of the modern cool-temperate brachiopod Terebratulina crossei collected at a water depth of 70m in Otsuchi Bay, northeastern Honshu, Japan. Brachiopod shells have been used as proxies of the δ13C values of dissolved inorganic carbon (DIC) (δ13CDIC) and seawater temperature/δ18O (δ18OSW) values to reconstruct the evolution of Phanerozoic oceans. To identify more reliable shell portions as the proxies, we conducted a rigorous time-series comparison of δ13C and δ18O values between the brachiopod shells and calcite precipitated in isotopic equilibrium with ambient seawater (equilibrium calcite) (δ13CEC and δ18OEC values, respectively). Samples were collected from the outer and inner surfaces of the secondary shell layer along the maximum growth axis (ontogenetic-series and inner-series samples, respectively). The ontogenetic-series δ13C values, which showed regular annual and irregular non-annual cycles, partly fell in but were mostly less than the range of the δ13CEC values. The δ13C cycles were often associated with one or two minor negative peaks. The peaks were likely resulted from an increased incorporation of respiration-derived 12C due to elevated metabolic activity during spawning. The ontogenetic-series δ18O values showed distinct seasonal variations and were mostly within the range of δ18OEC values. The amplitude of the δ18O profiles was relatively large during the younger fast-growth stage, and decreased during the senescent slow-growth stage. The inner-series δ13C and δ18O values of individual shells varied within narrow ranges. The inner-series δ13C values were close to the minimum δ13CEC values. The inner-series δ18O values were in the upper range of the δ18OEC values. Kinetic isotope fractionation effects were evident, but its degree varied among different shells. We identified the shell portions reliably recording past ocean environments. The best estimates of annual average δ13CDIC values were obtained from ontogenetic-series δ13C values near the anterior shell edge and from inner-series δ13C values; those of the annual average seawater temperature were obtained from ontogenetic-series δ18O values from the entire transect and from the fast-growth stage.
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U2 - 10.1016/j.gca.2015.08.006
DO - 10.1016/j.gca.2015.08.006
M3 - Article
AN - SCOPUS:84943773399
VL - 170
SP - 301
EP - 320
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
ER -