A rapid cleaning method for diatoms

Abstract

We describe here a protocol for cleaning diatoms when time is short and the amount of sample is very limited. Essentially, the method consists of drying material onto coverslips and cleaning it directly in situ using nitric acid (or hydrogen peroxide), which is evaporated to dryness. After washing twice or a few times with deionized water, the coverslips are ready for mounting in resin for light microscopy as usual, or attachment to stubs for scanning electron microscopy. Besides speed, the method has the advantage that it often preserves some frustules intact or leaves their different elements (and stages of valve formation) closely associated with each other. Examples where the method is especially advantageous are to clean small aliquots of cultures for identification or to act as vouchers, or to explore diversity of the most abundant species in natural material (e.g., periphyton). It is less suitable for counts in ecological or palaeoecological studies. We tabulate the many other cleaning methods to provide context for the new method described here.

Keywords:

• cleaning procedure
• diatoms
• digestion
• nitric acid cleaning
• peroxide cleaning
• preparation methods

Acknowledgements

We thank Nil Álvarez (IRTA technician) and Konstantinos Tsochas (Eurodyssey Programme trainee fellow at IRTA) for their help in testing the method; Ruth Hollands and Frieda Christie (RBGE) for technical assistance with SEM; and Paul Hamilton and two anonymous reviewers for very helpful comments. The authors also acknowledge support from the CERCA Programme/Generalitat de Catalunya. The Royal Botanic Garden Edinburgh is supported by the Scottish Government’s Rural and Environment Science and Analytical Services Division.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Rosa Trobajo http://orcid.org/0000-0001-9498-3797

David G. Mann http://orcid.org/0000-0003-0522-6802