Assessment of Chemical Mixtures and Groundwater Effects on Daphnia magna Transcriptomics

摘要

Small organisms can be used as biomonitoring tools to assess chemicals in the environment Chemical stressors are especially hard to assess and monitor when present as complex mixtures. Here, fifteen polymerase chain reaction assays targeting Daphnia mogia genes were calibrated to responses elicited in D. magna exposed for 24 h to fire different doses each of the munitions constituents 2,4,6-trinitrotoluene, 2,4-dmitro-toluene, 2,6-dinitrotoluene, trinitrobenzene, dinitrobenzene, or l,34-trinitro-13,5-triazacydoheiane. A piecewise-linear model for log-fold expression changes m gene assays was used to predict response to munttions mixtures and contaminated groundwater under the assumption that chemical effects were additive. The correlations of model predictions with actual expression changes ranged from 0.12 to 0.78 wifli an average of 0,5. To better understand possible mixture effects, gene expression changes from all treatments were compared using high-density microarrays. Whereas mixtures and groundwater exposures had genes and gene (unctions in common with single chemical exposures, unique functions were also affected, which was consistent with the nonadditivity of chemical effects in these mixtures. These results suggest that, while gene behavior in response to chemical exposure can be partially predicted based on chemical exposure, estimation of the composition of mixtures from chemical responses is difficult without further understanding of gene behavior in mixtures. Future work will need to examine additive and nonadditive mixture effects using a much greater range of different chemical classes in order to clarify the behavior and predictability of complex mixtures.