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Diatoms tell the truth about our environment

Description: The Phenom™ proves to be a valuable and cost-effective instrument for imaging and classification of diatoms at the Dutch Water Treatment & Control Laboratories.

Recommended Product: Phenom G2 Desktop Scanning Electron Microscope

Diatoms provide information on both the biological integrity of the ecosystem and those factors likely to be causing any observed changes. Researchers are rapidly developing new techniques for using diatoms to provide even more quantitative and accurate inferences of ecosystem condition, and diatoms are being included in a growing number of local and regional-scale monitoring programs. The Phenom™ proves to be a valuable and cost-effective instrument for imaging and classification of diatoms at the Dutch Water Treatment & Control Laboratories.

Diatoms as water quality indicators

Diatoms are single-cell algae which can be identified from the shape of their skeleton. Diatoms are divided into two groups based on overall symmetry of the cell walls; radially symmetrical forms are informally called “centric” diatoms while bilaterally symmetrical forms are referred to as “pennate” diatoms. One remarkable aspect of these organisms is that they have cell walls made of glass (silicon dioxide). The glass cell walls are perforated and ornamented with many holes, which are usually arranged in definite patterns. The nature of these perforations as well as their orientation and densities help in the identification of diatom species.

Diatoms have cell walls which are perforated and ornamented with many holes.
Diatoms have cell walls which are perforated and ornamented with many holes.

They live in all our lakes and rivers and are of interest to aquatic system managers as indicators of water quality – acidity, salinity, organic pollution load and pollutant types. There are more than 7000 species living in fresh and brackish water, population mix and species diversity reflecting environmental conditions. They supplement chemical analysis, covering too short a time span, with additional and some-times more reliable information. Their continually changing classification must be mastered since more than 400 new taxons are described each year.

Long term perspective

Although diatoms are widely distributed as a group, most species occur only in habitats with specific physical, chemical, and biological characteristics. Ecologists have long made practical use of this habitat specificity by collecting and analyzing individual species and community data to determine the quality or condition of aquatic habitats. Both long-term monitoring of specific lake and stream habitats and analysis of diatom remains (that become part of the sedimentary record of lakes) allow scientists to obtain a unique long-term historical perspective on these ecosystems. This perspective is especially valuable in assessing the long-term effects of human activities on aquatic and terrestrial ecosystems.

References

Charles, D.F., R.W. Battarbee, I. Renberg, H. Van Dam, and J.P. Smol. 1989. Paleoecological analysis of lake acidification trends in North America and Europe using diatoms and chrysophytes.
Pages 207-276 in S.A. Norton, S.E. Lindberg, and A.L. Page, eds. Acidic precipitation. Soils, aquatic processes, and lake acidification. Vol. 4. Springer-Verlag, New York.

Acknowledgement:

This application note has been created with the help from
Mr. B. Pex, Waterboard Roer & Overmaas, The Netherlands.

Detail of the cell wall of a diatom.
Detail of the cell wall of a diatom.
Diatoms in their natural aquatic habitat.
Diatoms in their natural aquatic habitat.



Diatoms tell the truth about our environment app note