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Abstract Foraminifera are unicellular organisms that inhabit the oceans. They play an important role in the global carbon cycle and record valuable paleoclimate information through the uptake of trace elements such as strontium into their calcitic shells. Understanding how foraminifera control their internal fluid composition to make calcite is important for predicting their response to ocean acidification and for reliably interpreting the chemical and isotopic compositions of their shells. Here, we model foraminiferal calcification and strontium partitioning in the benthic foraminiferaCibicides wuellerstorfiandCibicidoides mundulusbased on insights from inorganic calcite experiments. The numerical model reconciles inter-ocean and taxonomic differences in benthic foraminifer strontium partitioning relationships and enables us to reconstruct the composition of the calcifying fluid. We find that strontium partitioning and mineral growth rates of foraminiferal calcite are not strongly affected by changes in external seawater pH (within 7.8–8.1) and dissolved inorganic carbon (DIC, within 2100–2300 μmol/kg) due to a regulated calcite saturation state at the site of shell formation.
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This content will become publicly available on December 1, 2026
Planktonic foraminifera regulate calcification according to ocean density
Abstract Planktonic foraminifera are key contributors to the oceanic carbon cycle. In pelagic environments, carbonate production by planktonic biomineralizers regulates ocean-atmosphere carbon dioxide exchange and exports surface carbon to the deep ocean. Here we compare shell traits of three planktonic foraminifera species from the central Atlantic with a suite of environmental parameters to discern the factors underlying their variations. Our analysis revealed that calcification in foraminifera is associated with seawater density and depends on species habitat depth, whereas foraminifera bulk shell densities may serve as a seawater density proxy, regardless of species. We observe that their shell weights increased with habitat depth, enabling the living cells to adjust their overall density to match that of the surrounding liquid. This suggests that calcification in nonmotile organisms has a buoyancy regulatory function and will respond to the anthropogenically driven reductions in ocean density (oceanic rarefication), with potential consequences for the carbon cycle.
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- Award ID(s):
- 2305234
- PAR ID:
- 10649638
- Publisher / Repository:
- Nature
- Date Published:
- Journal Name:
- Communications Earth & Environment
- Volume:
- 6
- Issue:
- 1
- ISSN:
- 2662-4435
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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