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Oceanography

Bacteria and silica cycling

Nature volume 397, pages 475–476 (1999)Cite this article

As a graduate student who enjoyed counting plankton under the microscope, I felt frustrated when confronted with an occasional sample that contained almost nothing except a few bacteria flitting or gliding about on the slide. The bacteria were apparently responsible for the barrenness of the slide, and had thrived because the sample had escaped its shot of preservative. Mysteriously, the silica shells of the diatoms had also vanished, although they were beautifully preserved in the treated samples. The observation contradicted the view that diatom shells are of no nutritional value and that their dissolution is controlled by physico-chemical and not biological factors.

Diatoms dominate phytoplankton blooms in the ocean, so the finding adds to our growing understanding of how planetary elemental cycles are geared to each other. In the emerging view, wind-blown dust from the continents increases ocean productivity by providing iron2, which is often a limiting element. In large areas of the open ocean — the high-nutrient, low-chlorophyll (HNLC) regions — iron deficiency constrains growth rates not only of phytoplankton2 but also of bacteria3. In some regions, silicic acid (dissolved silica) is in short supply relative to the major nutrients nitrate and phosphate4. For instance the N:P ratio across the Southern Ocean varies by less than 10% but the Si:N ratio ranges from 0.15 in the north to 3 in the south. Because diatom demand for Si:N is about 1, the discrepancy in dissolved nutrient ratios indicates that nitrogen is recycled more efficiently within the surface layer than silica. Hence the finding that microbial breakdown of protein also enhances silica dissolution1 has interesting implications, because until now diatoms have been thought to protect their surface by secreting mucus (carbohydrates).

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Figure 1: The case of the disappearing diatoms — an example of Bidle and Azam's experiments1.
Figure 2: Fortress Fragilariopsis kerguelensis, the shells of which dominate the diatom ooze under the Antarctic Circumpolar Current.

References

  1. Bidle, K. & Azam, F. Nature 397, 508–512 (1999).

    Article  ADS  CAS  Google Scholar 

  2. Falkowski, P. G., Barber, R. T. & Smetacek, V. Science 281, 200–206 (1998).

    Google Scholar 

  3. Pakulski, J. D.et al. Nature 383, 133–134 (1996).

    Article  ADS  CAS  Google Scholar 

  4. Dugdale, R. C., Wilkerson, F. P. & Minas, H. J. Deep-Sea Res. I 42, 697–719 (1995).

    Google Scholar 

  5. Treguer, P.et al. Science 268, 375–379 (1995).

    Google Scholar 

  6. Hutchins, D. A. & Bruland, K. W. Nature 393, 561–564 (1998).

    Article  ADS  CAS  Google Scholar 

  7. Takeda, S. Nature 393, 774–777 (1998).

    Article  ADS  CAS  Google Scholar 

  8. Verity, P. G. & Smetacek, V. Mar. Ecol. Prog. Ser. 130, 277–293 (1996).

    Google Scholar 

  9. Kröger, N. & Sumper, M. Protist 149, 213–219 (1998).

    Google Scholar 

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  1. the Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-27570, Bremerhaven, Germany

    Victor Smetacek

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  1. Victor Smetacek
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Smetacek, V. Bacteria and silica cycling. Nature 397, 475–476 (1999). https://doi.org/10.1038/17219

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