Potential for cross-contamination of diatom DNA samples when using toothbrushes

The use of toothbrushes and similar devices for sampling diatoms from hard surfaces is a well-established approach. Toothbrushes are routinely cleaned reused when analysis by light microscopy. This paper looks at the scale contamination encountered this technique used to sample metabarcoding analyses, as well be expected if stream, rather than distilled water, wash stones. Although some attributable was detected, read numbers were low had no effect on index calculation or ecological status estimates. However, primary focus study thoroughly document diversity in sample, then even small level may unacceptable more stringent measures required.