A Bioluminescent Bacterial Toxicity Assay for Tropical Marine Environments

Bioassays using bioluminescent bacteria offer a cost-effective and efficient alternative to standard toxicity assays for assessing contaminant risks in the environment, with applications in water quality assessments and effluent screening spanning decades. However, most bacterial bioassays utilize Aliivibrio fischeri in a low-throughput format under temperate conditions, limiting their suitability for tropical marine environments. Furthermore, conventional A. fischeri assays rely on short exposure periods (e.g., 5, 15, 30 min) and luminescence as the sole toxicity endpoint, reducing their applicability for deriving water quality guideline values. This study aimed to develop a high-throughput, and cost-effective assay using the tropical bioluminescent bacterium Vibrio azureus (Lum-31), incorporating toxicity endpoints suitable for both acute and chronic contaminant assessment in tropical marine conditions. Using copper and zinc as reference toxicants, we demonstrated the repeatability of the acute luminescence assay at 15 and 30 min, with increased sensitivity compared to A. fischeri assays. In addition, integrating an ecologically relevant endpoint (specific growth rate) and a chronic exposure period (> 24 h) enabled comparisons of V. azureus sensitivity with other taxa in sensitivity distributions for copper and zinc species. This approach enhances the ecological relevance of the assay and improves its applicability for future ecological risk assessments in tropical marine environments.