Planktonic foraminifera iodine&thinsp;∕&thinsp;calcium ratio: is it a proxy for dissolved oxygen in the ocean?

Guarinos, Vincent; Tachikawa, Kazuyo; Garcia, Marta; Siani, Giuseppe; Revel, Marie; Schulz, Hartmut; Sierro, Francisco; Chalk, Thomas

doi:10.5194/bg-23-5477-2026

Articles | Volume 23, issue 15

https://doi.org/10.5194/bg-23-5477-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-23-5477-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 23, issue 15

Research article

|

10 Aug 2026

Research article |

| 10 Aug 2026

Planktonic foraminifera iodine ∕ calcium ratio: is it a proxy for dissolved oxygen in the ocean?

Vincent Guarinos, Kazuyo Tachikawa, Marta Garcia, Giuseppe Siani, Marie Revel, Hartmut Schulz, Francisco Sierro, and Thomas Chalk

Supplement

https://doi.org/10.5194/bg-23-5477-2026-supplement

Data sets

Dataset: Guarinos et al., 2026 article "Planktonic foraminifera Iodine/Calcium ratio: is it a proxy for dissolved oxygen in the ocean?" V. Guarinos et al. https://doi.org/10.5281/zenodo.18390413

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Short summary

Direct observations indicate a decline in ocean oxygen concentration. The complexity of surface oxygen variability is linked to physical and biochemical parameters. To investigate past oxygen variability, foraminiferal I/Ca proxy must be calibrated. Here, we determine the drivers of the proxy using a database of modern samples. From our results, oxygen is the principal driver of the I/Ca proxy. We highlight its complex behaviour, while reinforcing its use for palaeoceanographic reconstructions.