Abstract
ABSTRACTUltraviolet (UV) radiation has multiple consequences to freshwater organisms. Some zooplanktons use photoenzymatic repair (PER), which is a process that utilizes ultraviolet-A and visible light (photorepair radiation, PRR) to repair ultraviolet-B-induced DNA damage. Some zooplanktons also repair damage via nucleotide excision repair (NER), which is a radiation-independent enzymatic process. Our objective was to determine the effects of UV radiation, including the use of PER and NER on the cladocerans Diaphanosoma birgei, Scapholeberis mucronata, and Moina spp. Based on studies with Daphnia, we hypothesized that the use of PER and NER varies with temperature and across species. The three taxa were exposed to UV-B radiation followed by photorepair radiation (+PRR) or no photorepair radiation (−PRR). The occurrences of PER and NER were determined indirectly by monitoring the survival and reproduction after exposure. Experiments were performed at 10, 15, 20, 25, and 30 °C. S. mucronata and Moina spp. use PER effectively at all temperatures, whereas D. birgei uses PER less effectively and only at warmer temperatures. S. mucronata and Moina spp. use NER more effectively at colder temperatures, while D. birgei uses little to no NER. These findings have implications on how these organisms may adapt to changing UV and thermal conditions.
Highlights
Climate change continues to be a threat to aquatic ecosystems throughout the world, resulting in increased water surface temperatures and enhanced thermal stratification (H€ader et al 2015)
During the UV-B and PRR exposure at 10 C, none of the D. birgei in any of the treatments (+PRR, ¡PRR, and dark control) survived. We found that both S. mucronata and Moina appear to use photoenzymatic repair (PER) effectively at a wide range of temperatures (10–30 C), whereas D. birgei appears to have more limited use of PER and only at warmer temperatures (20–30 C)
Temperature is more important for UV-exposed S. mucronata and Moina
Summary
Climate change continues to be a threat to aquatic ecosystems throughout the world, resulting in increased water surface temperatures and enhanced thermal stratification (H€ader et al 2015). The effects of ultraviolet (UV) radiation on aquatic organisms in the context of climate change may be beneficial or detrimental, depending on the complex interactions between multiple environmental factors (Williamson et al 2014). These factors include stratospheric ozone, which influences ambient UV; chromophoric dissolved organic matter, which influences underwater UV transparency; and temperature, which can influence organisms’ response to UV (Williamson et al 2014). Some species of freshwater zooplanktons have adaptions that allow them to better withstand UV-B radiation, including photoenzymatic repair (PER), a mechanism in which visible.
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