Ba/Ca of stylasterid coral skeletons records dissolved seawater barium concentrations

James Kershaw*, Joseph A. Stewart, Ivo Strawson, Maria Luiza de Carvalho Ferreira, Laura F. Robinson, Katharine R. Hendry, Ana Samperiz, Andrea Burke, James W.B. Rae, Rusty D. Day, Peter J. Etnoyer, Branwen Williams, Vreni Häussermann

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

4 Citations (Scopus)


The concentration of dissolved barium in seawater ([Ba]SW) is influenced by both primary productivity and ocean circulation patterns. Reconstructing past subsurface [Ba]SW can therefore provide important information on processes which regulate global climate. Previous Ba/Ca measurements of scleractinian and bamboo deep-sea coral skeletons exhibit linear relationships with [Ba]SW, acting as archives for past Ba cycling. However, skeletal Ba/Ca ratios of the Stylasteridae – a group of widely distributed, azooxanthellate, hydrozoan coral – have not been previously studied. Here, we present Ba/Ca ratios of modern stylasterid (aragonitic, calcitic and mixed mineralogy) and azooxanthellate scleractinian skeletons, paired with published proximal hydrographic data. We find that [Ba]SW and sample mineralogy are the primary controls on stylasterid Ba/Ca, while seawater temperature exerts a weak secondary control. [Ba]SW also exerts a strong control on azooxanthellate scleractinian Ba/Ca. However, Ba-incorporation into scleractinian skeletons varies between locations and across depth gradients, and we find a more sensitive relationship between scleractinian Ba/Ca and [Ba]SW than previously reported. Paired Sr/Ca measurements suggest that this variability in scleractinian Ba/Ca may result from the influence of varying degrees of Rayleigh fractionation during calcification. We find that these processes exert a smaller influence on Ba-incorporation into stylasterid coral skeletons, a result consistent with other aspects of their skeletal geochemistry. Stylasterid Ba/Ca ratios are therefore a powerful, novel archive of past changes in [Ba]SW, particularly when measured in combination with temperature sensitive tracers such as Li/Mg or Sr/Ca. Indeed, with robust [Ba]SW and temperature proxies now established, stylasterids have the potential to be an important new archive for palaeoceanographic studies.
Original languageEnglish
Article number121355
JournalChemical Geology
Early online date1 Feb 2023
Publication statusPublished - 5 Apr 2023

Bibliographical note

Funding Information:
Funding for this work was provided by a NERC GW4+ Doctoral Training Partnership (NE/S007504/1) studentship awarded to J.K., an Antarctic Bursary awarded to J.A.S, and NERC grants awarded to L.F.R. ( NE/S001743/1 ; NE/R005117/1 ; NE/N003861/1; NE/X00127X/1 ). Cruise DY081 was funded by European Research Council starting grant ICY-LAB (Grant Agreement 678371 ).

Publisher Copyright:
© 2023 The Authors


  • Ba/Ca
  • Barium
  • Scleractinia
  • Stylasteridae
  • Coral


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