Anthropogenic activities and changing climate patterns have attributed to increases in UV radiation (UVR) reaching Earth’s surface, and these changes are affecting aquatic ecosystems in various ways. Bdelloid rotifers are aquatic microinvertebrates that play a prominent part in aquatic food webs. These animals have well-known abilities that allow them to survive adverse conditions, including resistance to UVR. This characteristic may be particularly important for populations living in the dynamic, ephemeral waters of the North American desert southwest. Bdelloids from this area are typically exposed to episodes of prolonged drying and direct UVR exposure, and this may be especially true for those that undergo aeolian transport. In this study, we investigate UVR resistance by measuring UVR-induced mortality in order to determine any differences between those from locations experiencing different year-round UVR intensities and/or drought episodes. Bdelloids were cultured from three Chihuahuan Desert sources (a permanent man-made lake, rehydrated dust, and an ephemeral desert rock pool) and a natural lake in Wisconsin. Water was also collected for dissolved organic carbon (DOC) analyses in late summer 2015 and early winter 2016. Bdelloids were exposed to UVR in the laboratory under four UVR exposure treatments following three desiccation regimes; mortality was assessed after exposure.
Total DOC concentrations were significantly greater at the rock pool than at either of the two lakes (ANOVA, F=10.06, p<0.05; Tukey, p<0.05), with the rock pool’s winter concentrations being significantly greater than the summer concentrations for the Wisconsin lake and the concentrations for both seasons for the man-made lake (Tukey, p<0.05). Preliminary UV exposure results show a trend in mortality with response to desiccation time and exposure levels (GLM, p<0.001); there was no observed variation in mortality for the four populations. Differences in DOC concentration across the three locations tested may suggest different protection potentials against UVR. Seasonal DOC differences may also play an important factor in some habitats. Further exposure experiments will be undertaken to determine any relationship in mortality and bdelloid culture source. DOC concentrations will also be compared to mortality to identify a possible association. This study will provide insights into UVR resilience in bdelloids across different habitat types and will enhance our knowledge of the effects aquatic biota may face in the future.