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Development of high throughput assays in four species relevant to ecological hazard assessment
Citation:
Flynn, K., M. Le, K. Bush, M. Morshead, AND J. Hoang. Development of high throughput assays in four species relevant to ecological hazard assessment. U.S. Environmental Protection Agency, Washington, DC, EPA/600/X-23/344, 2022.
Impact/Purpose:
Efforts to evaluate ecological risks of chemicals could benefit from increased throughput in ecological toxicity testing. For instance, by modifying standard protocols and methods to allow such tests to be conducted in smaller volumes on multi-well plates. Thus, high throughput bioassays will be developed for ecologically relevant and taxonomically diverse species (fathead minnow, Daphnia magna, insect larvae, and algae) to provide data that is anchored to phenotypic responses that are directly applicable to standard aquatic toxicology endpoints (e.g., growth, survival, and reproduction). The operating procedures to conduct the high throughput bioassays and a description of the various measurements will be developed. In addition, these measurements will be linked to transcriptomic datasets that are produced from organisms from the same exposures.
Description:
Standardized aquatic toxicity test guidelines provide defensible data for use in ecological risk assessments. However, constraints imposed by these assay designs limit the number of tests that can be conducted and inefficiently consume test chemical. To increase throughput and improve the efficiency of aquatic toxicity testing, assays using 96-well microplates and four commonly tested species (Pimephales promelas, Daphnia magna, Chironomus dilutus, and Raphidocelis subcapitata) were developed by modifying previously published protocols to fit both specific species and microplate requirements. Water quality parameters and baseline (i.e., control) survival for these assay designs met the acceptance criteria for US Environmental Protection Agency test guidelines. Using the developed four assays, 27 chemicals across a wide range of chemical classes were tested and survival datacollected. Toxicity estimates (i.e., LC50s or EC50s) from these assays were compared to published data from more traditional test designs. Based upon an intraclass correlation coefficient of 0.61, data from these assays showed good agreement with published data. These results offer compelling evidence for the technical validity of our assay designs, and further support effort toward high-throughput ecological toxicity testing. In addition, these assays will be used as the foundation for collection of high-content datasets for the purpose of first tier ecological hazard screening.