33 Boron in diatoms

• Published in: Journal of Phycology
• Main Authors: Deyhle, A., Hodge, V., Lewin, R. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2003
• Subjects: Iceland
• Online Access: http://dx.doi.org/10.1111/j.0022-3646.2003.03906001_33.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.0022-3646.2003.03906001_33.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.0022-3646.2003.03906001_33.x

Lewin, J. C. (1965) showed that boron is required for the growth of Cylindrotheca fusiformis , and, presumably, other diatoms too. It may be involved in cellular metabolism, as in higher plants, or incorporated by accident or design into the siliceous skeletons (frustules), since B 2 O 3 has been proven to replace SiO 2 (e.g. in siliceous rocks). Thus the frustules may contain or bear at their surface a proportion of borosilica, which might reduce their solubility in water. (Incidentally, boron has also been implicated in human bone formation and stability (Newnham, 1994). Deyhle (2002), who determined the content of B in calcareous skeletons of marine foraminifera and compared the isotopic ratios of 11 B /10 B with that in the environmental sea water, found the B content to be generally less than 10 ppm We sought comparable values for diatom frustules, washed and bleached to remove salts and organic matter, if possible without leaching away any of the B that could be present. We studied fossil diatomite from Lompoc, California; diatomaceous ooze from Myvatn, Iceland; natural plankton diatoms harvested from the sea; and pure cultures of marine and freshwater diatoms grown in the laboratory. By contrast with foraminiferan calcite, our data indicated that diatom frustules contain up to 1,600 ppm of boron, with a more marked enrichment of the lighter isotope. Rough calculations indicate that the B 2 O 3 , even if concentrated at the frustule surface, might be enough to reduce the solubility of the frustules. Our B‐isotope enrichment data range between +3.9 to −0.2‰, indicating that diatoms preferentially incorporate the light 10 B . Such values can provide indications to physico‐chemical conditions under which the skeletons were deposited (cf. Lewin, E. et al. 2000) Data will be presented.