Inhibition of Daphnia pulex swimming behavior by volatile petroleum products: Optical monitoring in a novel sealed chamber.

Since volatile organic chemicals (VOCs) evaporate at room temperatures, concentration-response studies are challenging in conventional assay systems, and new methods are needed to evaluate the effects of exposure that minimize VOC loss. In this study, the effects of three VOCs, benzene, toluene, and ethylbenzene on Daphnia pulex swimming behavior were evaluated. A novel bioassay system consisting of a sealed single-well cylindrical stainless-steel chamber with a glass bottom and top permit infrared light transmission and recording of movement with a digital camera. Exposure to increasing concentrations of toluene, benzene and ethylbenzene in water media significantly affected swimming behavior by decreasing swimming distance and increasing turning behavior. This novel assay system enables the study of VOCs at consistent exposure levels, and an upgraded multi-well version will increase throughput to test VOC mixtures for potential interactions among constituents that affect behavioral and transcriptomic responses.