ISO 10253:2016

Overview

ISO 10253:2016 specifies a standardized laboratory method for assessing the inhibition of growth of two unicellular marine algae - Skeletonema sp. and Phaeodactylum tricornutum - by substances and mixtures present in sea water or environmental water samples (for example, effluents and elutriates). The test quantifies algal toxicity by measuring reductions in specific growth rate over a typical incubation period of 72 ± 2 hours, with cell-density measurements at least every 24 ± 2 hours. The method is intended for substances that are readily water‑soluble and not rapidly removed from the test medium.

Key topics and technical requirements

• Test organisms: Unialgal (non-axenic) strains of Skeletonema sp. or Phaeodactylum tricornutum recommended by recognized culture collections.
• Principle and endpoint: Inhibition is expressed as a reduction in specific growth rate relative to controls; effective concentrations (EC(r)) represent concentrations producing an x% reduction.
• Test medium: Uses filtered natural or synthetic sea water (approx. salinity 33 g/kg). Synthetic sea water composition and nutrient stock solutions are specified to ensure reproducible growth conditions.
• Procedures:
  • Prepare growth medium, pre-culture and inoculum.
  • Establish dilution series and stock solutions of test substances.
  • Incubate test and control batches for 72 ± 2 h under controlled illumination and temperature.
  • Measure cell density (particle counter, microscope counting chamber, or validated indirect methods like fluorimetry/spectrophotometry).
• Quality and validity: Includes validity criteria, requirements for equipment (inert materials, avoid copper), sterility/filtration of media, and data interpretation (growth curves, % inhibition calculations).
• Scope limits: Best suited to readily soluble compounds; for poorly soluble, volatile, metal compounds or complex matrices, follow modifications in related standards.

Applications and users

ISO 10253:2016 is used for:

• Algal toxicity testing and ecotoxicological hazard assessment of chemicals and mixtures.
• Environmental monitoring of marine effluents, coastal discharges and sediment elutriates.
• Regulatory testing, product safety dossiers, and compliance verification by environmental laboratories. Primary users include environmental and analytical laboratories, ecotoxicologists, wastewater treatment operators, chemical manufacturers, and regulatory authorities conducting marine bioassays.

Related standards

• ISO 14442 - guidelines for algal tests with poorly soluble materials, volatiles, metals and waste water.
• ISO 5667‑16 - guidance on sampling for biotesting of water samples.
• ISO/TC 147 (Water quality) provides the technical committee context.

Keywords: ISO 10253:2016, water quality, marine algal growth inhibition test, Skeletonema sp., Phaeodactylum tricornutum, algal toxicity testing, ECx, test medium, effluent testing, environmental monitoring.