Antioxidant Defences in Planktonic Crustaceans Exposed to Different Underwater Light Irradiances in Andean Lakes

In freshwater environments direct biological effect of ultraviolet radiation (UVR) result from absorption of specific wavelengths by macromolecules and alteration of biochemical processes. Indirect effects are related to UVR interaction with water and dissolved organic carbon to form chemically reactive species (ROS: reactive oxygen species). Zooplankton photoprotection includes mycosporine-like amino acids, pigments, production of quenching agents and antioxidant enzymes. The relative importance of each mechanism would depend on the organisms. In this study, we determined the antioxidant enzyme activities Catalase (CAT) and Glutathione-S-transferase (GST) in the copepod Boeckella gracilipes and the cladoceran Ceriodaphnia dubia in three Andean lakes of the North-Patagonia region. There were differences in antioxidant enzymes expression between copepods and cladocerans. CAT was significantly higher in C. dubia than in B. gracilipes whereas GST was similar in both species. The comparison of B. gracilipes enzyme activity in the three lakes showed also differences in GST but not in CAT. DOC decreases the exposure by absorption of UVR but simultaneously acts as photosensitizer producing ROS and their successive toxic products in the surface waters. We discuss that comparisons among lakes of different DOC should be considered carefully because lake physico-chemicals parameters, as well as food web structure, will difficult any predictions on the net effect of DOC.