Ecotoxicological Assessment of Surfactant Pollution Using Pyrocystis lunula Bioluminescence

Bioluminescence-based bioassays have emerged as sensitive tools for assessing the ecotoxicological effects of marine contaminants. Among marine microplankton, bioluminescent dinoflagellates offer ecologically relevant responses due to their position at the base of the food web and their sensitivity to membrane-active compounds. In this study, the toxic effects of the anionic surfactants linear alkylbenzene sulfonate (LAS) and sodium dodecyl sulfate (SDS), widely used in detergents and frequently detected in coastal waters, were evaluated using the bioluminescent dinoflagellate Pyrocystis lunula . Cultures in the stationary growth phase were exposed for 24 and 48 h to increasing concentrations of LAS (0.1–50.0 mg L⁻¹) and SDS (5–50.0 mg L⁻¹), following standardized ecotoxicological guidelines. Bioluminescence inhibition was quantified at the nocturnal emission peak using a Tecan Infinite® M200 Pro Luminometer, and complemented by cell density and viability assessments. LAS induced a clear concentration-dependent inhibition of bioluminescence, with an estimated IC₅₀ of 38.11 mg L⁻¹ after 24 h, while SDS exhibited higher toxicity, particularly at concentrations ≥ 25 mg L⁻¹. Combined exposure to LAS and SDS resulted in stronger inhibitory effects than single-compound treatments. Notably, bioluminescence proved more sensitive than cell density in detecting early sublethal effects, indicating disruptions in membrane integrity and metabolic activity prior to cell death. These results highlight the suitability of P. lunula bioluminescence as a rapid, cost-effective, and ecologically relevant tool for monitoring surfactant contamination in marine environments and supporting coastal water-quality assessment.