TY - JOUR
T1 - Evaluation of geochemical records as a paleoenvironmental proxy in the hypercalcified demosponge Astrosclera willeyana
AU - Asami, Ryuji
AU - Kinjo, Akira
AU - Ohshiro, Daiki
AU - Naruse, Tohru
AU - Mizuyama, Masaru
AU - Uemura, Ryu
AU - Shinjo, Ryuichi
AU - Ise, Yuji
AU - Fujita, Yoshihisa
AU - Sakamaki, Takashi
N1 - Funding Information:
We are grateful to a chief editor (Prof. H. Kawahata) and two anonymous reviewers for their helpful and valuable suggestions and comments on the manuscript. We also thank M. Kondo (Okinawa Institute of Science and Underwater Technology) for help with field surveys and Dr. H. Fujimura, M. Chinen, and Y. Akamine (University of the Ryukyus) for help with experiments.
Funding Information:
This research was supported by the Japan Society for the Promotion of Science KAKENHI (Grant-in-Aid for Scientific Research) Grant numbers 26550012, 26707028, and 18K18522 to RA and 15H01729 to RU, and the NEXT Program Grant Number GR083 to TS. Acknowledgements
Publisher Copyright:
© 2020, The Author(s).
PY - 2020/12/1
Y1 - 2020/12/1
N2 - The geochemistry of the calcium carbonates of marine organisms is an excellent proxy for reconstruction of the paleoceanographic history. However, previous studies of hypercalcified demosponges (sclerosponges) are considerably fewer than those of corals, foraminifers, and bivalves. Here, we investigated stable oxygen (δ18O) and carbon (δ13C) isotopes and minor and trace element (Mg, Sr, Ba, Pb, and U) to Ca ratios of 36 living sclerosponges (Astrosclera willeyana) collected from Kume Island in the Ryukyu Islands, southwestern Japan, to evaluate the utility of geochemistry as a paleoenvironmental proxy. The δ18O, δ13C, and Sr/Ca deviations of the coevally precipitated skeleton were extremely small and almost constant at all skeletal portions, strongly suggesting that within-skeletal variations in the chemical components are negligibly small for non-symbiotic sclerosponges. Mean δ18O, δ13C, and Sr/Ca values (N = 36), falling within a quite narrow range, showed no significant evidence for intraspecific (inter-specimen) variations in the sclerosponges. The sclerosponges δ18O and δ13C were consistent with those of the aragonites precipitated in isotopic equilibrium with seawater at the growth site. The sclerosponge Sr/Ca was close to that of inorganically precipitated aragonite, and the estimated partition coefficient of 1.1 (almost unity) is identical to previously reported values for different species (Ceratoporella nicholsoni). Consequently, these results suggest that A. willeyana sclerosponge, having little vital effects on the geochemistry, is a robust indicator of paleocean environments (seawater δ18O, temperature, and dissolved inorganic carbon δ13C). Further, our evaluation study documents that sclerosponges living in deeper ocean environments can support the reconstruction of spatial and vertical paleoceanographic changes in conjunction with coral proxy records. The sclerosponge U/Ca showed little within-skeletal and intraspecific variations, but the heterogeneity and individual difference of the Mg/Ca, Ba/Ca, and Pb/Ca were relatively large, the reasons of which still remain unresolved. [Figure not available: see fulltext.]
AB - The geochemistry of the calcium carbonates of marine organisms is an excellent proxy for reconstruction of the paleoceanographic history. However, previous studies of hypercalcified demosponges (sclerosponges) are considerably fewer than those of corals, foraminifers, and bivalves. Here, we investigated stable oxygen (δ18O) and carbon (δ13C) isotopes and minor and trace element (Mg, Sr, Ba, Pb, and U) to Ca ratios of 36 living sclerosponges (Astrosclera willeyana) collected from Kume Island in the Ryukyu Islands, southwestern Japan, to evaluate the utility of geochemistry as a paleoenvironmental proxy. The δ18O, δ13C, and Sr/Ca deviations of the coevally precipitated skeleton were extremely small and almost constant at all skeletal portions, strongly suggesting that within-skeletal variations in the chemical components are negligibly small for non-symbiotic sclerosponges. Mean δ18O, δ13C, and Sr/Ca values (N = 36), falling within a quite narrow range, showed no significant evidence for intraspecific (inter-specimen) variations in the sclerosponges. The sclerosponges δ18O and δ13C were consistent with those of the aragonites precipitated in isotopic equilibrium with seawater at the growth site. The sclerosponge Sr/Ca was close to that of inorganically precipitated aragonite, and the estimated partition coefficient of 1.1 (almost unity) is identical to previously reported values for different species (Ceratoporella nicholsoni). Consequently, these results suggest that A. willeyana sclerosponge, having little vital effects on the geochemistry, is a robust indicator of paleocean environments (seawater δ18O, temperature, and dissolved inorganic carbon δ13C). Further, our evaluation study documents that sclerosponges living in deeper ocean environments can support the reconstruction of spatial and vertical paleoceanographic changes in conjunction with coral proxy records. The sclerosponge U/Ca showed little within-skeletal and intraspecific variations, but the heterogeneity and individual difference of the Mg/Ca, Ba/Ca, and Pb/Ca were relatively large, the reasons of which still remain unresolved. [Figure not available: see fulltext.]
KW - Astrosclera willeyana
KW - Isotope equilibrium
KW - Minor and trace elements
KW - Oxygen and carbon isotopic composition
KW - Paleoenvironmental proxy
KW - Sclerosponge
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U2 - 10.1186/s40645-020-00329-z
DO - 10.1186/s40645-020-00329-z
M3 - Article
AN - SCOPUS:85084428728
VL - 7
JO - Progress in Earth and Planetary Science
JF - Progress in Earth and Planetary Science
SN - 2197-4284
IS - 1
M1 - 15
ER -
