Sponge skeletons as an important sink of silicon in the global oceans

Article metrics


Silicon (Si) is a pivotal element in the biogeochemical and ecological functioning of the ocean. The marine Si cycle is thought to be in internal equilibrium, but the recent discovery of Si entries through groundwater and glacial melting have increased the known Si inputs relative to the outputs in the global oceans. Known outputs are due to the burying of diatom skeletons or their conversion into authigenic clay by reverse weathering. Here we show that non-phototrophic organisms, such as sponges and radiolarians, also facilitate significant Si burial through their siliceous skeletons. Microscopic examination and digestion of sediments revealed that most burial occurs through sponge skeletons, which, being unusually resistant to dissolution, had passed unnoticed in the biogeochemical inventories of sediments. The preservation of sponge spicules in sediments was 45.2 ± 27.4%, but only 6.8 ± 10.1% for radiolarian testa and 8% for diatom frustules. Sponges lead to a global burial flux of 1.71 ± 1.61 TmolSi yr−1 and only 0.09 ± 0.05 TmolSi yr−1 occurs through radiolarians. Collectively, these two non-phototrophically produced silicas increase the Si output of the ocean to 12.8 TmolSi yr−1, which accounts for a previously ignored sink that is necessary to adequately assess the global balance of the marine Si cycle.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Digestion kinetics of BSi and LSi pure materials.
Fig. 2: Diatom and sponge BSi skeletons during digestion in 1% sodium carbonate at 85 °C.
Fig. 3: Contributors of BSi in superficial sediments.

Data availability

The authors declare that all other data supporting the findings of this study are available within the article and its Supplementary Information. Further additional data are available at the institutional repository of the Spanish National Research Council (CSIC), http://hdl.handle.net/10261/184130.

The map layers that contain the ocean geomorphology features were downloaded from www.bluehabitats.com, except for coral reefs, which were obtained from the World Resource Institute (www.wri.org). The extension of radiolarian-rich sediments was calculated using the map layers available at the www.earthbyte.org/webdav/ftp/papers/Dutkiewicz_etal_seafloor_lithology/.


  1. 1.

    Nelson, D. M., Tréguer, P., Brzezinski, M. A., Leynaert, A. & Quéguiner, B. Production and dissolution of biogenic silica in the ocean: revised global estimates, comparison with regional data and relationship to biogenic sedimentation. Glob. Biogeochem. Cycles 9, 359–372 (1995).

  2. 2.

    Tréguer, P. & Pondaven, P. Silica control of carbon dioxide. Nature 406, 358–359 (2000).

  3. 3.

    Harriss, R. C. Biological buffering of oceanic silica. Nature 212, 275–276 (1966).

  4. 4.

    Calvert, S. E. Silica balance in the ocean and diagenesis. Nature 219, 919–920 (1968).

  5. 5.

    DeMaster, D. J. The supply and accumulation of silica in the marine environment. Geochim. Cosmochim. Acta 45, 1715–1732 (1981).

  6. 6.

    Tréguer, P. et al. The silica balance in the world ocean: a reestimate. Science 268, 375–379 (1995).

  7. 7.

    Laruelle, G. G. et al. Anthropogenic perturbations of the silicon cycle at the global scale: key role of the land-ocean transition. Glob. Biogeochem. Cycles 23, GB4031 (2009).

  8. 8.

    Tréguer, P. J., De La & Rocha, C. L. The world ocean silica cycle. Ann. Rev. Mar. Sci. 5, 477–501 (2013).

  9. 9.

    Frings, P. J., Clymans, W., Fontorbe, G., De La Rocha, C. & Conley, D. J. The continental Si cycle and its impact on the ocean Si isotope budget. Chem. Geol. 425, 12–36 (2017).

  10. 10.

    Hawkings, J. R. et al. Ice sheets as a missing source of silica to the polar oceans. Nat. Commun. 8, 14198 (2017).

  11. 11.

    Rahman, S., Aller, R. C. & Cochran, J. K. The missing silica sink: revisiting the marine sedimentary Si cycle using cosmogenic 32Si. Glob. Biogeochem. Cycles 31, 1559–1578 (2017).

  12. 12.

    Rahman, S., Tamborski, J. J., Charette, M. A. & Cochran, J. K. Dissolved silica in the subterranean estuary and the impact of submarine groundwater discharge on the global marine silica budget. Mar. Chem. 208, 29–42 (2019).

  13. 13.

    Tréguer, P. J. The Southern Ocean silica cycle. C. R. Geosci. 346, 279–286 (2014).

  14. 14.

    Maldonado, M. et al. Siliceous sponges as a silicon sink: an overlooked aspect of the benthopelagic coupling in the marine silicon cycle. Limnol. Oceanogr. 50, 799–809 (2005).

  15. 15.

    Maldonado, M., Navarro, L., Grasa, A., Gonzalez, A. & Vaquerizo, I. Silicon uptake by sponges: a twist to understanding nutrient cycling on continental margins. Sci. Rep. 1, 30 (2011).

  16. 16.

    Maldonado, M., Riesgo, A., Bucci, A. & Rützler, K. Revisiting silicon budgets at a tropical continental shelf: silica standing stocks in sponges surpass those in diatoms. Limnol. Oceanogr. 55, 2001–2010 (2010).

  17. 17.

    Maldonado, M., Ribes, M. & Van Duyl, F. C. Nutrient fluxes through sponges: biology, budgets, and ecological implications. Adv. Mar. Biol. 62, 114–182 (2012).

  18. 18.

    Chu, J. W. F., Maldonado, M., Yahel, G. & Leys, S. P. Glass sponge reefs as a silicon sink. Mar. Ecol. Prog. Ser. 441, 1–14 (2011).

  19. 19.

    Jochum, K. P. et al. Whole-ocean changes in silica and Ge/Si ratios during the Last Deglacial deduced from long-lived giant glass sponges. Geophys. Res. Lett. 44, 11,555–511,564 (2017).

  20. 20.

    Jochum, K. P., Wang, X., Vennemann, T. W., Sinha, B. & Müller, W. E. G. Siliceous deep-sea sponge Monorhaphis chuni: a potential paleoclimate archive in ancient animals. Chem. Geol. 300–301, 143–151 (2012).

  21. 21.

    Hurd, D. C. Interactions of biogenic opal, sediment and seawater in the Central Equatorial Pacific. Geochim. Cosmochim. Acta 37, 2257–2282 (1973).

  22. 22.

    Mortlock, R. A. & Froelich, P. N. A simple method for the rapid determination of biogenic opal in pelagic marine sediments. Deep -Sea Res. I 36, 1415–1426 (1989).

  23. 23.

    Eggimann, D. W., Manheim, F. T. & Betzer, P. R. Dissolution and analysis of amorphous silica in marine sediments. J. Sediment Petrol. 50, 215–225 (1980).

  24. 24.

    Kamatani, A. & Oku, O. Measuring biogenic silica in marine sediments. Mar. Chem. 68, 219–229 (2000).

  25. 25.

    Paasche, E. Silicon and the ecology of marine plankton diatoms. II Silicate-uptake kinetics in five diatom species. Mar. Biol. 19, 262–269 (1973).

  26. 26.

    Müller, P. J. & Schneider, R. An automated leaching method for the determination of opal in sediments and particulate matter. Deep-Sea Res I 40, 425–444 (1993).

  27. 27.

    Conley, D. J. An interlaboratory comparison for the measurements of biogenic silica in sediments. Mar. Chem. 63, 39–48 (1998).

  28. 28.

    Ragueneau, O. et al. A new method for the measurement of biogenic silica in suspended matter of coastal waters: using Si:Al ratios to correct for the mineral interference. Cont. Shelf Res 25, 697–710 (2005).

  29. 29.

    Heinze C. in The Silicon Cycle: Human Perturbations and Impacts on Aquatic Systems (eds Ittekkot, V., Unger, D., Humborg, C. & An, N. T.) 229–244 (SCOPE Series Vol. 66, Island Press, 2006).

  30. 30.

    Murillo, F. J., Kenchington, E., Lawson, J. M., Li, G. & Piper, D. J. W. Ancient deep-sea sponge grounds on the Flemish Cap and Grand Bank, northwest Atlantic. Mar. Biol. 163, 1–11 (2016).

  31. 31.

    Maldonado M., et al. in Marine Animal Forests: The Ecology of Benthic Biodiversity Hotspots (eds Rossi, S., Bramanti, L., Gori, A. & Orejas, C.) 145–183 (Springer International, 2017).

  32. 32.

    Dayton, P. K. Observations of growth, dispersal and population dynamics of some sponges in McMurdo Sound, Antarctica. Colloq. Int. Cent. Natl Rech. Sci. 291, 271–282 (1979).

  33. 33.

    Gutt, J., Böhmer, A. & Dimmler, W. Antarctic sponge spicule mats shape macrobenthic diversity and act as a silicon trap. Mar. Ecol. Prog. Ser. 480, 57–71 (2013).

  34. 34.

    Barthel, D. & Gutt, J. Sponge associations in the eastern Weddell Sea. Antarct. Sci. 4, 137–150 (1992).

  35. 35.

    Lisitzin A. P. in The Micropaleontology of Oceans (eds Funnell, B. M. & Riedel W. R.) 173–195 (Cambridge Univ. Press, 1971).

  36. 36.

    Dutkiewicz, A., Müller, R. D., O’Callaghan, S. & Jónasson, H. Census of seafloor sediments in the world’s ocean. Geology 43, 795–798 (2016).

  37. 37.

    Boltovskoy, D., Kling, S. A., Takahashi, K. & Bjørklund, K. World atlas of distribution of recent Polycystina (Radiolaria). Palaeontol. Electron. 13, 1–230 (2010).

  38. 38.

    Van Cappellen, P. & Qiu, L. Biogenic silica dissolution in sediments of the Southern Ocean. I. Solubility. Deep-Sea Res II 44, 1109–1128 (1997).

  39. 39.

    DeMaster, D. J. The accumulation and cycling of biogenic silica in the Southern Ocean: revisiting the marine silica budget. Deep-Sea Res II 49, 3155–3167 (2002).

  40. 40.

    Ragueneau, O. et al. Biodeposition by an invasive suspension feeder impacts the biogeochemical cycle of Si in a coastal ecosystem (Bay of Brest, France). Biogeochemistry 75, 19–41 (2005).

  41. 41.

    Harris, P. T., Macmillan-Lawler, M., Rupp, J. & Baker, E. K. Geomorphology of the oceans. Mar. Geol. 352, 4–24 (2014).

  42. 42.

    Bett, B. J. & Rice, A. L. The influence of hexactinellid sponge spicules on the patchy distribution of macrobenthos in the Porcupine Seabight (bathyal NE Atlantic). Ophelia 36, 217–226 (1992).

  43. 43.

    Laguionie-Marchais, C., Kuhnz, L. A., Huffard, C. L., Ruhl, H. A. & Smith, K. L. Jr Spatial and temporal variation in sponge spicule patches at Station M, northeast Pacific. Mar. Biol. 162, 617–624 (2015).

  44. 44.

    Howell, K.-L., Piechaud, N., Downie, A.-L. & Kenny, A. The distribution of deep-sea sponge aggregations in the North Atlantic and implications for their effective spatial management. Deep-Sea Res I 115, 309–320 (2016).

  45. 45.

    Sospedra, J. et al. Identifying the main sources of silicate in coastal waters of the Southern Gulf of Valencia (Western Mediterranean Sea). Oceanologia 60, 52–64 (2018).

  46. 46.

    Ehlert, C. et al. Transformation of silicon in a sandy beach ecosystem: insights from stable silicon isotopes from fresh and saline groundwaters. Chem. Geol. 440, 207–218 (2016).

  47. 47.

    Lecher, A. Groundwater discharge in the Arctic: a review of studies and implications for biogeochemistry. Hydrology 4, 41 (2017).

  48. 48.

    DeMaster D. J. in Marine Particles: Analysis and Characterization (eds Hurd, D. C. & Spenser, D. W.) 363–367 (Geophysical Monographs Vol. 63, American Geophysical Union, 1991).

  49. 49.

    Sandford, F. Physical and chemical analysis of the siliceous skeletons in six sponges of two groups (Demospongiae and Hexactinellida). Microsc. Res. Tech. 62, 336–355 (2003).

  50. 50.

    Hurd D. C. in Silicon Geochemistry and Biochemistry (ed. Aston, S. R.) 187–244 (Academic, 1983).

  51. 51.

    DeMaster D. J. in Sediments, Diagenesis, and Sedimentary Rocks (ed. Mackenzie, F. T.) 97–98 (Treatise on Geochemistry, Vol. 7, Elsevier, 2003).

Download references


We thank the British Ocean Sediment Core Research Facility (BOSCORF-NOC) for providing access to cores 1, 12, 14 and 16. We also thank E. Kenchington, C. Campbell, K. Jarrett and J. Murillo (BIO) for making the data and sediment of cores 2 and 4 available. A. Ehrhold (IFREMER) is thanked for core 3, M. A. Mateo (CEAB) for core 7 and T. Whiteway (Australian Geosciences) for core 15. R. Ventosa and M. Abad are thanked for helping with the DSi autoanalyser determinations, B. Dursunkaya for helping with the digestion experiments and P. Talberg and L. Cross for providing strains of the Thalassiossira diatom. J. Krause is especially thanked for comments and insight on the manuscript. This study, which spanned five years, benefitted from funding by two grants of the Spanish MINECO (CTM2012-37787 and CTM2015-67221-R). Financial support by the European Union’s Horizon 2020 research and innovation program to the SponGES project (grant agreement 679849) is acknowledged.

Author information

M.M. designed the study and experiments. Sediment and BSi digestions were conducted by M.M., M.L.A., C.S., M.G.-P. and C.G. Sediment cores were collected by G.E. Light microscopy determination of the BSi was conducted by M.L.A., C.S., M.G.-P. and C.G. under supervision of M.M. SEM and energy dispersive X-ray spectrometry analyses were conducted by M.M. and C.S. Data analyses were conducted by M.M. and M.L.A. and ArcGis mapping by M.G.-P. M.M. wrote the manuscript, with invaluable inputs made by M.L.A. and the rest of co-authors at different stages of the process.

Correspondence to Manuel Maldonado.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary information

Supplementary data tables 1–4, Supplementary figs 1–5, Supplementary dicussion, Supplementary methods and Supplementary references.

Supplementary data table 1

Supplementary Methods data (Table 1).

Supplementary data table 2

Supplementary Methods data (Table 2).

Supplementary data 1

Supplementary data for burial depth and Si preservation.

Supplementary data 2

Supplementary data for deposition rate and sponge and radiolarian burial rate.

Supplementary data 3

Supplementary data for global ocean Si burial and preservation.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark