Mesophotic foraminiferal-algal nodules play a role in the Red Sea carbonate budget

Valentina Alice Bracchi*, Sam J. Purkis, Fabio Marchese, Megan K.B. Nolan, Tullia Isotta Terraneo, Silvia Vimercati, Giovanni Chimienti, Mattie Rodrigue, Ameer Eweida, Francesca Benzoni

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


During two scientific expeditions between 2020 and 2022, direct surveys led to the discovery of free-living mesophotic foraminiferal-algal nodules along the coast of the NEOM region (northern Saudi Arabian Red Sea) where they form an unexpected benthic ecosystem in mesophotic water depths on the continental shelf. Being mostly spheroidal, the nodules are transported en masse down slope, into the deep water of the basin, where they stop accreting. Radiometric dating informs that these nodules can be more than two thousand years old and that they collectively contribute up to 66 g m−2 year−1 to the mesophotic benthic carbonate budget and account for at least 980 megatons of calcium carbonate, a substantial contribution considering the depauperate production of carbonate by other means in this light-limited environment. Our findings advance the knowledge of mesophotic biodiversity and carbonate production, and provide data that will inform conservation policies in the Saudi Arabian Red Sea.

Original languageEnglish (US)
Article number288
JournalCommunications Earth and Environment
Issue number1
StatePublished - Dec 2023

Bibliographical note

Funding Information:
This research was undertaken in accordance with the policies and procedures of the King Abdullah University of Science and Technology (KAUST). Permission relevant for KAUST to undertake the research was obtained from the applicable governmental agencies in the Kingdom of Saudi Arabia. We would like to thank OceanX and the crew of OceanXplorer for their operational and logistical support for the duration of the expedition. In particular, we would like to acknowledge the ROV and submersible teams for data acquisition and sample collection, and the OceanXplorer crew for support of scientific operations on board. This work was supported by KAUST (FCC/1/1973-50-01, FCC/1/1973-49-01), and baseline research funds to F. Benzoni). G. Chimienti was supported by the Italian Ministry of Education, University and Research (PON 2014–2020, Grant AIM 1807508-1, Linea 1). Maps throughout this paper were created using ArcGIS® software by Esri. ArcGIS® and ArcMap™ are the intellectual property of Esri and are used herein under license. Copyright © Esri. All rights reserved. For more information about Esri® software, please visit .

Publisher Copyright:
© 2023, Springer Nature Limited.

ASJC Scopus subject areas

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)


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