Genomic methods simultaneously report both specific and holistic assessments of biological systems an ideal property when assessing the potential impact of chemicals on ecosystems and the environment. To date, however, genomics infrastructures have not been developed for one of the most commonly used and accepted environmental toxicity monitoring organisms Ceriodaphnia dubia. In this Phase II proposal, we expand on our Phase I work by sequencing a large number of C. dubia cDNAs using high-throughput sequencing. After sequence assembly and annotation, we will print a 4x70,000-element oligonucleotide microarray representing at least 10,000 distinct genes. This array will be used to perform toxicity tests on four reference toxins with different chemical properties. Each of the chemicals tested will be assayed at three different concentrations. We will define expression signatures for each of the toxins and attempt to correlate expression results with known toxicity mechanisms. In addition, we will perform one 7-day exposure at a low concentration of a toxin known to have chronic effects and note how the expression profile changes over time. Finally, we will assemble a highly annotated Ceriodaphnia database that has been integrated into a bioinformatics infrastructure that will allow easy interpretation and sharing of hybridization data.This project aims to develop DNA microarrays for the identification and understanding of environmental toxicity in the one of the key organisms used for testing environmental toxicity the water flea Ceriodaphnia dubia. DNA microarrays are a uniquely powerful method of identifying and characterizing environmental toxicity due to their ability to combine many specific tests to achieve a global understanding of toxic effects. High throughput DNA sequencing and NimbleGen based array synthesis will be used to produce fully annotated and commercial ready microarrays for use both in academic and commercial settings. In addition to commercially available Ceriodaphnia microarrays, Eon Corporation will facilitate use of these arrays through contracted performance of microarray based tests, and distribution of an expression analysis database that incorporates identification, function, and expression information for each element/gene. Technologies for environmental toxicity testing have fallen 15 years behind those now commonly used in pharmaceutical toxicity testing. Without new technologies for identifying and characterizing environmental toxins, the increasing variety and quantity of chemicals released into the environment will mount untold environmental and human health tolls.