Responses of the ecological characteristics and antioxidant enzyme activities in Rotaria rotatoria to UV-B radiation

UV-B radiation is an increasing threat to aquatic organisms and also a potential driving force for zooplankton population dynamics. To explore the ecological effects of UVR on rotifers and the responses of antioxidant system against UVR, the acute lethal effects, the life history strategies, population growth, and antioxidant enzyme activities were assessed in the Bdelloid Rotaria rotatoria after exposure to UV-B radiation. The results indicated that the persistence of tolerance in rotifer to stress was playing a more vital role than the radiation dose in survival. The larger the culture volume, the weaker the lethal effect. Rotifers prolonged their first reproductive time and shortened their reproductive period and longevity with the increasing of radiation dose, and the fecundity was significant inhibited by UV-B radiation. These responses can be taken as energy trade-off to retard their mortality. The population density of the rotifers increased at the lowest dose of radiation and then descended with the increasing of UVR dose, and this pattern was also corroborated by detecting the content of SOD and CAT, which suggested that hormesis also applies to R. rotatoria under UV-B radiation stress. The enzyme SOD has higher level of content and more sensitive to low UVR than CAT.