Comparison of bioassessment results and costs between preserved and unpreserved macroinvertebrate samples from streams

Abstract

The choice to use or not use a preservative before sorting macroinvertebrate samples (i.e., dead specimens vs. living specimens) is based on studies not solely focused on the effects of preservation. Using identical sample processing protocols, we compared preserved and unpreserved samples for the following parameters: (1) the number of taxa and individuals for each major macroinvertebrate group, (2) ecological quality classes calculated with a multimetric index developed for the assessment of small Dutch lowland streams, and (3) costs of sample processing. We collected macroinvertebrate samples from three lowland streams in the Netherlands. At each site, we collected six replicate samples, of which three samples were preserved and three were not. Significantly different numbers of Ephemeroptera individuals and Hydracarina taxa and individuals were collected from preserved samples compared to unpreserved samples. In assessments based on these individual metrics, standardiza- tion of sample processing will be required. In streams with Ephemeroptera, the preservation of samples is necessary to optimize the number of Ephemeroptera individuals collected. In streams that contain Hydracarina, the preservation of samples will result in an underestimation of the number of Hydracarina taxa and individuals present. In only one instance there was a difference in ecological quality between preserved and unpreserved samples, indicating that assessing small Dutch lowland streams does not require standardization of sample preservation as part of the sample processing protocol. We detected no significant differences in sample processing costs between preserved and unpreserved samples.

NoMBSI: a new, Non-lethal Method for Benthos Sampling and Identification for use in biological monitoring of flowing waters: preliminary results

“…Moreover, the incorrectness of taxa recognition seems a largely random process susceptible to the influence of individual experience with this type of image analysis. Then again, some of the incorrectly identified animals could be present in NC samples, only to be damaged and/or go missing during sorting in the laboratory with a view to preservation and storage (e.g., Keizer-Vlek et al, 2011). Still, some differences in taxonomic composition between identifiers can be neglected for degradation assessment purposes due to the fact that the particular quality classes are usually described as a range of values and not a single value (e.g., Bis & Mikulec, 2013).…”