Impacts of Coral Growth on Geochemistry: Lessons From the Galápagos Islands

Emma V. Reed, Diane M. Thompson, Julia E. Cole, Janice M. Lough, Neal E. Cantin, Anson H. Cheung, Alexander Tudhope, Lael Vetter, Gloria Jimenez, R. Lawrence Edwards

Research output: Contribution to journalArticlepeer-review

Abstract

Coral geochemical climate reconstructions can extend our knowledge of global climate variability and trends over time scales longer than those of instrumental data. However, such reconstructions can be biased by coral growth and skeletal architecture, such as growth troughs, off-axis corallite orientation, and changing growth direction. This study quantifies the impact of skeletal architecture and growth on geochemistry using measurements of coral skeletal density, extension rate, and calcification rate, and uses these metrics to improve paleoclimate reconstructions. We present paired geochemistry-density records at Wolf Island, Galápagos, from three Porites lobata corals: two new paired density and geochemistry records from one fossil coral, and new density data from two previously published modern geochemistry records. We categorize each sampling transect used in this record by the quality of its orientation with respect to skeletal architecture. We observe relationships between geochemistry and density that are not detected using extension or calcification rate alone. These density-geochemistry relationships likely reflect both the response of coral growth to environmental conditions and the nonclimatic impact of skeletal architecture on geochemistry in suboptimal sampling transects. Correlations of density with Sr/Ca, Ba/Ca, and Mg/Ca are consistent with the Rayleigh fractionation model of trace element incorporation into coral skeletons. Removing transects with suboptimal skeletal architecture increases mean reconstructed SST closer to instrumental mean SST, and lowers errors of reconstruction by up to 20%. These results demonstrate the usefulness of coral density data for assessing skeletal architecture and growth when generating coral paleoclimate records.

Original languageEnglish (US)
Article numbere2020PA004051
JournalPaleoceanography and Paleoclimatology
Volume36
Issue number4
DOIs
StatePublished - Apr 2021

Bibliographical note

Funding Information:
We gratefully acknowledge the Gal?pagos National Park and Charles Darwin Research Station, especially Galo Quezada and Sonia Cisneros, for facilitating our 2010 coral collection; Colin Chilcott, Meriwether Wilson, Roberto Pepolas, Diego Ruiz, Jenifer Suarez, and the captain and crew of the Queen Mabel for field support; Stephan Hlohowskyj, Sydnie Lemieux, Keeley Lyons-Letts, Constance Shaver, and Maria Snyder for assisting with geochemical data collection; and Grace Frank and Eric Matson for facilitating densitometry analyses. This work was funded by the National Science Foundation Grants 1401326/1829613 and 0957881 to J. E. Cole, UK Natural Environment Research Council Grant NE/H009957 to A. Tudhope, and an NSF Graduate Research Fellowship and the Australia-Americas PhD Research Internship Program to E. V. Reed.

Funding Information:
We gratefully acknowledge the Galápagos National Park and Charles Darwin Research Station, especially Galo Quezada and Sonia Cisneros, for facilitating our 2010 coral collection; Colin Chilcott, Meriwether Wilson, Roberto Pepolas, Diego Ruiz, Jenifer Suarez, and the captain and crew of the Queen Mabel for field support; Stephan Hlohowskyj, Sydnie Lemieux, Keeley Lyons‐Letts, Constance Shaver, and Maria Snyder for assisting with geochemical data collection; and Grace Frank and Eric Matson for facilitating densitometry analyses. This work was funded by the National Science Foundation Grants 1401326/1829613 and 0957881 to J. E. Cole, UK Natural Environment Research Council Grant NE/H009957 to A. Tudhope, and an NSF Graduate Research Fellowship and the Australia‐Americas PhD Research Internship Program to E. V. Reed.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

Keywords

  • Coral density
  • coral geochemistry
  • coral growth
  • eastern Pacific

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