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Biogenic silica (BSi) is the equivalent to the terms Opal , Biogenic opal, and amorphous opaline silica. BSi is essential to many plants and animals. Chemically, BSi is hydrated Silica (SiO2•''n''H2O).

Diatom s in both fresh and salt water extract silica from the water to use as a component of their cell walls. Likewise, some Holoplankton ic Protozoa ( Radiolaria ), some Sponge s, and some plants (leaf Phytolith s) use silicon as a structural material. Silicon is known to be required by chicks and rats for growth and skeletal development. Silicon is in human Connective Tissue s, Bone s, Teeth , Skin , Eye s, Gland s and Organs . It is a major constituent of Collagen which helps keep our skin Elastic , and it helps Calcium in maintaining bone strength.

BSi is silica that originates from the production out of Dissolved Silica . BSi can either be accumulated "directly" in Marine Sediment s (via export) or be transferred back into dissolved silica in the water column.

Increasingly, and Nutrient Cycling (De La Rocha, 2006; Leng and Barker, 2006). This is a particularly valuable approach considering the role of Diatom s in global carbon cycling. In addition, isotope analyses from BSi are useful for tracing past climate changes in regions such as in the Southern Ocean , where few biogenic Carbonate s are preserved.


BSI PRODUCTION

The mean daily BSi rate strongly depends on the region:
  • Coastal Upwelling : 46 mmol m-2 d-1

  • Sub- Arctic Pacific]]: 18 mmol m-2 d-1

  • Southern Ocean: 3–38 mmol m-2 d-1

  • mid-ocean Gyre s: 0.2–1.6 mmol m-2 d-1


Likewise, the integrated annual BSi production strongly depends on the region:
  • Coastal upwelling: 3 . 1012 mol yr-1

  • Subarctic Pacific: 8 . 1012 mol yr-1

  • Southern Ocean: 17–37 . 1012 mol yr-1

  • mid-ocean gyres: 26 . 1012 mol yr-1


BSi production is controlled by:
  • Dissolved Silica availability, however, half saturation constant ''Kµ'' for silicon-limited growth is lower than ''Ks'' for silicon Uptake .

  • Light availability: There is no direct light requirement; silicon uptake at 2x depth of Photosynthesis ; silicon uptake continues at night but cells must be actively growing.

  • Micronutrient availability.



BSI DISSOLUTION

BSi dissolution is controlled by:



BSI PRESERVATION

BSi preservation is measured by:

BSi preservation is controlled by:
  • Sedimentation rate;

  • Porewater dissolved silica concentration: saturation at 1.100 µmol/L;

  • Surface coatings: dissolved Al modifies solubility of deposited biogenic silica particles, dissolved silica can also Precipitate with Al as Clay or Al-Si coatings.



REFERENCES

  • Brzezinski, M. A. (1985). “The Si:C:N ratio of marine diatoms: Interspecific variability and the effect of some environmental variables.” ''Journal of Phycology'' 21(3): 347-357.

  • De La Rocha, C.L. (2006). "Opal based proxies of paleoenvironmental conditions." ''Global Biogeochemical Cycles'' 20. doi:10.1029/2005GB002664.

  • Dugdale, R. C. and F. P. Wilkerson (1998). “Silicate regulation of new production in the equatorial Pacific upwelling.” ''Nature'' 391(6664): 270.

  • Dugdale, R. C., F. P. Wilkerson, et al. (1995). “The role of the silicate pump in driving new production.” ''Deep-Sea Research'' I 42(5): 697-719.

  • Leng, M.J. and Barker, P.A. (2006). "A review of the oxygen isotope composition of lacustrine diatom silica for palaeoclimate reconstruction." ''Earth Science Reviews'' 75:5-27.

  • Ragueneau, O., P. Treguer, et al. (2000). “A review of the Si cycle in the modern ocean: recent progress and missing gaps in the application of biogenic opal as a paleoproductivity proxy.” ''Global and Planetary Change'' 26: 317-365.

  • Takeda, S. (1998). “Influence of iron availability on nutrient consumption ratio of diatoms in oceanic waters.” ''Nature'' 393: 774-777.

  • Werner, D. (1977). ''The Biology of Diatoms.'' Berkeley and Los Angeles, University of California Press.