The increase in penetration of ultraviolet radiation has been reported currently over southern South America. It would affect the photoprotective responses in biotic elements of freshwater ecosystems. An experiment was designed using pigmented adult individuals of the species Daphnia dadayana (Paggi 1999), Boeckella antiqua (Menu-Marque & Balseiro 2000), and Parabroteas sarsi (Mrazek 1901),. characteristic for shallow fishless ponds from South American plains (located between 41 and 53 degrees S latitude). The artificial ultraviolet radiation was involved in the experiment, with two levels of dissolved organic carbon (DOC), which would exert a protective effect against ultraviolet radiation. The results of this experiment showed that under conditions of low DOC concentrations, D. dadayana recorded a higher mortality,,while under low DOC concentrations, B. antiqua and R sarsi were not affected by ultraviolet radiation. Daphnids would be less tolerant to the exposure to ultraviolet radiation than pigmented calanoid copepods.