Paper in press: Iodine incorporation into deep-sea corals

I’m excited to report publication of a new study led by Lorena Sun investigating the incorporation of iodine into deep-sea scleractinian and bamboo corals. The paper is published in a Special Issue of Frontiers in Marine Sciences titled The Marine Iodine Cycle, Past, Present and Future.

Oxygen is vital for marine life, and understanding how its levels have changed over time is important, particularly given ongoing deoxygenation trends in the oceans. Iodine has recently emerged as a sensitive indicator of the oxygen content of seawater, specifically through its speciation between iodate–iodide, which shares similarities with the redox potential of dioxygen–water. Further, only iodate, the primary inorganic oxidized form of iodine, is incorporated into calcium carbonate. This raises the possibility that the iodine content of various sediments may hold clues to past oxygen levels, although the exact sediments that would reveal this information remain to be determined.

In Sun et al., we investigated the incorporation of iodine into deep-sea scleractinian and bamboo corals. Deep-sea corals are valuable recorders of seawater chemistry because they inhabit intermediate ocean depths where few other sediment records are available. They can also be accurately dated using radiometric techniques. Our findings revealed that iodine incorporation into scleractinian deep-sea corals is generally proportional to the ambient iodate concentrations that is, in turn, related to oxygen levels. However, when oxygen levels drop below 160 µmol/kg, the iodine content in scleractinian coral skeletons decreases significantly. This change in iodine content might be linked to changes in the coral’s biological functions below this oxygen threshold. Regardless, the existence of this threshold suggests that the iodine content of deep-sea corals can provide insights into past seawater oxygen levels, offering the potential to shed new light on climatic events in Earth’s history.

To learn more, check out the study here.

Full citation: Sun Y.-J., Robinson L.F., Parkinson I.J., Stewart J.A., Lu W., Hardisty D.S., Liu Q., Kershaw J., LaVigne M. and Horner T.J. (2023). Iodine-to-calcium ratios in deep- sea scleractinian and bamboo corals. Frontiers in Marine Sciences, 10, 1264380, doi:10.3389/fmars.2023.1264380.