Macroinvertebrate bioindicators are used in evaluating the biological quality of water. Traditionally, the biological material of the samples is preserved using formaldehyde, which is both a carcinogen and a sensitiser.

An alternative method

An alternative method published by the Direction Regionale de l’Environnement (DREN) Lorraine-France uses less hazardous means. It consists in elutriating the samples and separating a floating part concentrated in invertebrates which is preserved in ethanol and a sedimented part (sand, stones) that is frozen on the spot. Samples that are too small to elutriate are preserved entirely in ethanol, those that cannot be elutriated (sludge) are entirely frozen.