Changes in morphology and swimming dynamics of plankton by exposure to toxic chemicals are studied using a novel a new paradigm of image acquisition and computer vision system. Single cell ciliate Stentor coeruleus enclosed in a drop of water provide a means to automatically deposit many individual samples on a at surface. Chemicals of interest are automatically added to each drop while the dynamical and morphological changes are captured with an optical microscope. With computer vision techniques, we analyze the motion trajectory of each plankton sample, along with its shape information, quantifying the sub-lethal impact of chemicals on plankton health. The system enables large screening of hundreds of chemicals of environmental interest which may make their way into water habitats.