Bracchi et al. 2023

scientific article | Commun. Earth Environ.

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

Bracchi VA, Purkis SJ, Marchese F, Nolan MKB, Terraneo TI, Vimercati S, Chimienti G, Rodrigue M, Eweida A, Benzoni F


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.

Depth range
12- 705 m

Mesophotic “mentions”
36 x (total of 4891 words)

* Presents original data
* Focused on 'mesophotic' depth range
* Focused on 'mesophotic coral ecosystem'

Management and Conservation

Algae (Macro, Turf and Crustose Coralline)
Overall benthic (groups)
Protists (non-Symbiodiniaceae)

Saudi Arabia - Red Sea

In-situ instrumentation
Manned Submersible
Remotely Operated Vehicle (ROV)
Sonar / Multibeam
Surface-deployed sensors and samplers

Author profiles