Sensitivities to surfactants in Desmodesmus subspicatus, Daphnia galeata, and Bosmina longirostris

Abstract

We performed algal growth inhibition test on Desmodesmus subspicatus using a cationic surfactant benzalkonium bromide (BZK-Br), and acute toxicity tests on two cladoceran species, Daphnia galeata and Bosmina longirostris, using BZK-Br and an anionic surfactant sodium octyl sulfate (SOS). The 72-h 50% effective concentration (EC₅₀) with 95% confidence interval (CI) of initial BZK-Br to D. subspicatus was 60.3 µg L⁻¹ with 46.4–74.2 µg L⁻¹. The 48-h EC₅₀s (with those CIs) of BZK-Br to D. galeata and B. longirostris, estimated from the geometric mean concentrations, were 40.9 (33.0–48.8) µg L⁻¹ and 80.1 (68.1–92.0) µg L⁻¹, respectively. Unlike BZK-Br, the 48-h EC₅₀s (with those CIs) of SOS to D. galeata (335.9 mg L⁻¹, 248.5–423.3 mg L⁻¹) and B. longirostris (280.0 mg L⁻¹, 211.1–348.9 mg L⁻¹) were comparable. The present results were discussed about the difference in EC₅₀s to similar compounds on standard test organisms. We also mentioned that BZK-Br and SOS concentrations can present below the EC₅₀s in surface water, whereas they can affect biological interactions by interfering with colony formation response in D. subspicatus even at environmentally relevant concentrations.