Development of a semi-static algal growth inhibition test method

SETAC YES 2025 -- The OECD 201 Algal Growth Inhibition test guideline was developed as a static test design. However, a semi-static algal inhibition test would be more suitable for unstable chemicals of interest (COI). In ecotoxicology testing of unstable COI, a semi-static test approach is commonly taken [e.g., Daphnia sp., Acute Immobilisation Test (OECD 202)] to maintain test concentrations. A semi-static test could mitigate declining measured concentrations of COI due to degradation and the potential toxicity of breakdown products observed in static tests (Stuart et al. 2003). The current work investigated the potential of developing a semi-static test design capable of producing accurate and reproducible data; in addition to assessing the impact of a semi-static design in relation to the OECD 201 validity criteria.