75">An error term of ±2 IDEC units corresponding to the within-slide variability (replicability) should accompany all reported IDEC scores.
A deviation of ±3 points from the audit's IDEC scores should be considered as an acceptable difference. Considering the above-mentioned estimated error term of ±2 associated with all IDEC scores, an overall deviation of 7 would still be satisfactory.
Samples showing low diversity (Hill's N2 ≤5) should automatically be submitted for QA/QC.
A Bray–Curtis (analyst vs audit) similarity of ≥60% should also be included as a QA/QC criterion, and should increase to ≥70% for poorly diversified assemblages (Hill's N2 ≤5).
A diatom valve density of ≤15 per field of view should be targeted in order to reduce variability at the enumeration step.
The results of this study illustrate how a relatively simple and straightforward approach to QA/QC can greatly strengthen the reliability of ecological inferences from an index based on a group of organisms with a high taxonomical diversity. It also highlights the importance of regular communication between analysts in order to maintain a high degree of concordance within taxonomical identification.