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Published September 2025 | Version Supplemental material
Journal Article Open

Biogenic Si cycling along the Cocos Ridge: differences between in situ and ex situ extracted pore waters imply rapid rates of dissolved Si uptake upon core recovery

Creators

  • 1. ROR icon University of Southern California
  • 2. ROR icon University of Washington
  • 3. ROR icon Nanjing University
  • 4. ROR icon University of California, Santa Barbara
  • 5. ROR icon California Institute of Technology

Abstract

The cycling of silicon (Si) in marine sediments can have major impacts on global ocean nutrient dynamics and productivity. Si cycling in the sediment of the Cocos Ridge and overlying waters of the eastern equatorial Pacific was investigated using unique in situ and traditional ex situ pore water collection techniques as well as solid phase analysis, core incubation, and sediment trap collection. Si remineralization and burial fluxes show little variation between the four sites investigated, regardless of a ∼1600 m difference in water depth among stations. Dissolved Si concentrations in pore water from sediment depths >10 cm collected in situ were significantly and consistently higher than those collected ex situ implying a previously unrecognized sampling artifact associated with sediment core recovery and processing. The loss of dissolved Si in the ex situ pore waters is also associated with the fractionation of Si isotopes. In situ pore water δ30Si is lighter than ex situ pore water δ30Si at three of the four stations, though only significantly lighter at one. The preferential loss of light Si in ex situ pore waters is attributed to authigenic clay formation during core collection and transport from the cold, high pressure benthos to the ocean's surface. However, consistency between in situ and ex situ pore water Si gradients within 10 cm of the sediment water interface indicates remineralization fluxes previously determined using sediment core-derived pore waters remain accurate.

Copyright and License

© 2025 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Acknowledgement

This project would not have been possible without the crew and science party on board the R/V Sally Ride for cruise SR2113, whom we thank for their assistance in deploying and retrieving the instrumentation vital to this project. We thank Doug Hammond for the invaluable discussions and help he gave in interpreting the data. We also thank all the members of the Berelson Lab for their assistance in preparing the data for presentation. Seth Wieman and the USC machine shop are acknowledged for their work on the in situ sampler and we thank Holly Barnhart for her assistance with the fill water corrections. This work was funded by NSF grant OCE-1834475 to Will Berelson. We dedicate this work to our friend and colleague, Sijia Dong.

Conflict of Interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Research Support: Research support was provided by the National Science Foundation through grant OCE-1834475 to Will Berelson. There are no additional relationships, patents or activities to disclose.

Data Availability

In situ pore water data is stored in Cetiner et al. (2024).
Ex situ pore water data, Si isotope data, and solid phase data are stored in the following datasets in Mendeley Data:
Ex situ pore water: Quinan and Berelson (2025a).
Si isotope: Quinan et al. (2025).
Solid Phase: Quinan and Berelson (2025b).

Supplemental Material

Supplementary data 1 (DOCX)

Supplementary data 2 (DOCX)

Supplementary data 3 (DOCX)

 

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Additional details

Related works

Is supplemented by
Supplemental Material: https://ars.els-cdn.com/content/image/1-s2.0-S0967063725001128-mmc1.docx (URL)
Supplemental Material: https://ars.els-cdn.com/content/image/1-s2.0-S0967063725001128-mmc2.docx (URL)
Supplemental Material: https://ars.els-cdn.com/content/image/1-s2.0-S0967063725001128-mmc3.docx (URL)

Funding

National Science Foundation
OCE-1834475

Dates

Accepted
2025-07-01
Available
2025-07-04
Available online
Available
2025-07-10
Version of record

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Caltech groups
Division of Geological and Planetary Sciences (GPS)
Publication Status
Published