Iodine-to-calcium ratios in deep-sea scleractinian and bamboo corals

• Published in: Frontiers in Marine Science
• Main Authors: Sun, Yun-Ju, Robinson, Laura F, Parkinson, Ian J, Stewart, Joseph A, Lu, Wanyi, Hardisty, Dalton S, Liu, Qian, Kershaw, James, LaVigne, Michèle, Horner, Tristan J
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Earth Sciences > Oceanography; Seawater oxygen1; Iodine2; Deep-sea coral3; Scleractinian coral4; Bamboo coral5; Deep sea; Corals; Seawater; Biogeochemistry; Biological control; Deep water; Geochemistry; Hypoxia; Oxygenation; Archives; Mineralogy; Iodates; Oceans; Museums; Foraminifera; Radiometric dating; Carbonates; Calcium; Iodine; Biogeochemical cycles; Marine invertebrates; Oxidation; Oxygen; Archives & records; Biogeochemical cycle; Southern Ocean; Pacific; North Atlantic
• Online Access: https://hdl.handle.net/1983/1bac35c3-4b3d-4e69-919f-fb3022ce4fd4; https://research-information.bris.ac.uk/en/publications/1bac35c3-4b3d-4e69-919f-fb3022ce4fd4; https://doi.org/10.3389/fmars.2023.1264380; https://bris.idm.oclc.org/login?url=https://www.proquest.com/scholarly-journals/iodine-calcium-ratios-deep-sea-scleractinian/docview/2886738384/se-2?accountid=9730; https://media.proquest.com/media/hms/PFT/1/oxIAW?_a=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%3D%3D&_s=3TTSC4bXE4FtjrhIe38nKF3UZKU%3D; https://bris.on.worldcat.org/atoztitles/link?sid=ProQ:&issn=&volume=&issue=&title=Frontiers+in+Marine+Science&spage=&date=2023-11-07&atitle=Iodine-to-calcium+ratios+in+deep-sea+scleractinian+and+bamboo+corals&au=Sun,+Yun-Ju%3BRobinson,+Laura+F%3BParkinson,+Ian+J%3BStewart,+Joseph+A%3BLu,+Wanyi%3BHardisty,+Dalton+S%3BLiu,+Qian%3BKershaw,+James%3BLaVigne,+Mich%C3%A8le%3BHorner,+Tristan+J&id=doi:10.3389%2Ffmars.2023.1264380

The distribution of dissolved iodine in seawater is sensitive to multiple biogeochemical cycles, including those of nitrogen and oxygen. The iodine-to-calcium ratio (I/Ca) of marine carbonates, such as bulk carbonate or foraminifera, has emerged as a potential proxy for changes in past seawater oxygenation. However, the utility of the I/Ca proxy in deep-sea corals, natural archives of seawater chemistry with wide spatial coverage and radiometric dating potential, remains unexplored. Here, we present the first I/Ca data obtained from modern deep-sea corals, specifically scleractinian and bamboo corals, collected from the Atlantic, Eastern Pacific, and Southern Oceans, encompassing a wide range of seawater oxygen concentrations (10–280 μmol/kg). In contrast to thermodynamic predictions, we observe higher I/Ca ratios in aragonitic corals (scleractinian) compared to calcitic corals (bamboo). This observation suggests a strong biological control during iodate incorporation into deep-sea coral skeletons. For the majority of scleractinian corals, I/Ca exhibits a covariation with local seawater iodate concentrations, which is closely related to seawater oxygen content. Scleractinian corals also exhibit notably lower I/Ca below a seawater oxygen threshold of approximately 160 μmol/kg. In contrast, no significant differences in I/Ca are found among bamboo corals across the range of oxygen concentrations encountered (15–240 μmol/kg). In the North Atlantic, several hydrographic factors, such as temperature and/or salinity, may additionally affect coral I/Ca. Our results highlight the potential of I/Ca ratios in deep-sea scleractinian corals to serve as an indicator of past seawater iodate concentrations, providing valuable insights into historical seawater oxygen levels.