Development of a Rapid, Inexpensive Bioassay for Screening Contaminant Bioavailability in Sediment Using mRNA Profiling

PURPOSE: This technical note describes how the stress responses of common bioassay organisms can be used to identify toxic contaminants and their bioavailability in sediment. The freshwater non-biting midge, Chironomus tentans, responds to contaminant exposure by making proteins to detoxify chemicals or repair damage, in addition to other responses. Midges make new proteins by transcription, or copying, of genes into messenger RNA (mRNA) that are used to make many copies of a protein. A snapshot of what the midge is sensing and how it is responding can be found by looking at the mRNAs that are being made (mRNA profiling). Short exposures to common sediment contaminants result in patterns of mRNA profiles that indicate the class and type of the bioavailable chemical. Short analysis time and very high sample throughput enable this approach to be used as a means to rapidly screen large numbers of sediment samples for exposure and/or toxicity. These analyses are faster and cheaper than traditional priority pollutant analysis with the added potential of identifying bioavailable contaminants by the effect they cause in a bioassay organism. BACKGROUND: Decisions on the identification, assessment, and management of contaminated dredged material are frequently limited by information on how much risk the material poses.