Overview
ISO 6341:2012 specifies an internationally recognized acute toxicity test to assess water quality by measuring the inhibition of mobility (immobilization) of the water flea Daphnia magna Straus. The method determines a 24 h or 48 h EC50 (effective concentration causing immobilization of 50% of test organisms) and is applicable to soluble substances, stable suspensions, industrial and sewage effluents, treated/untreated waste water, aqueous extracts/leachates, fresh waters, sediment eluates and pore waters.
Key topics and technical requirements
- Test organism: Neonate Daphnia magna (<24 h old), from healthy laboratory cultures or hatched ephippia; avoid first-brood progeny.
- Endpoint: Immobilization - inability to swim during 15 s after gentle agitation. Outcome reported as 24 h EC50 or 48 h EC50.
- Test structure: Preliminary range-finding test followed by a definitive test; optional limit test (commonly at 100 mg/L if soluble or stable).
- Environment & conditions: Temperature-controlled room or incubator at (20 ± 2) °C; tests in the dark or under 16 h light / 8 h dark photoperiod; testing atmosphere free from toxic vapours/dusts.
- Media & water quality: Use pure water and appropriate dilution/culturing water (recommendations include pH around 7.8 ± 0.5, hardness ~225 ± 50 mg/L as CaCO3, dissolved oxygen >7 mg/L). Annex A provides preparation of Elendt M4 medium.
- Controls & reference checks: Include control batches and sensitivity checks (reference substance recommended: potassium dichromate). Validity criteria and reporting requirements are specified for reliable interpretation.
- Apparatus & reagents: Standard laboratory glassware, dissolved oxygen meter, sieves, pipettes; reagents of analytical grade.
Applications
ISO 6341:2012 is used for:
- Routine ecotoxicological screening of industrial discharges and municipal effluents.
- Regulatory compliance testing for water quality and wastewater permits.
- Product and chemical safety assessment during development and registration.
- Sediment pore-water and leachate testing for environmental risk assessment.
- Research in aquatic toxicology and environmental monitoring programs.
Who should use this standard
- Environmental and commercial testing laboratories
- Regulatory agencies and water-quality assessors
- Wastewater treatment operators and consultants
- Chemical manufacturers and ecotoxicologists
Related standards
Normative references include:
ISO 6341:2012 provides a robust, reproducible acute bioassay protocol for assessing aquatic toxicity using Daphnia magna - a key tool in water quality monitoring, effluent control and ecological risk assessment.
Open preview (PDF)Water quality — Determination of the inhibition of the mobility of Daphnia magna Straus (Cladocera, Crustacea) — Acute toxicity test