Abstract: A toxicity testing assay wherein a test sample is prepared with electrochromic dye and a living organism of the cladoceran order or other test organisms, and the sample is irradiated with alternately blue and yellow light to excite fluorescence. The successive groups of fluorescent emissions are then viewed at 90.degree. by a photomultiplier which develops equivalent alternate count outputs, and the count output is amplified and processed to develop data indicating (1) membrane potential of cells of the living organisms and (2) the total dye fluorescence which provides indication of deleterious effects to the organisms.

Abstract: A toxicity testing assay wherein a test sample is prepared with electrochromic dye such as Di-4-ANEPPS and a living organism of the cladoceran order, Daphnia Spp. or other test organisms, and the sample is irradiated with alternately blue and yellow light to excite fluorescence. The successive groups of fluorescent emissions are then viewed at 90.degree. by a photomultiplier which develops equivalent alternate count outputs, and the count output is amplified and processed to develop data indicating (1) membrane potential of cells of the living organisms and (2) the total dye fluorescence, which combined effects provides indication of deleterious effects to the organisms.