Methods for assessing the impacts of ultraviolet-B radiation on aquatic invertebrates

A standard methodology for assessing the impacts of simulated solar ultraviolet-B radiation (UV-B) on aquatic invertebrates was established. A solar simulator was used to expose a variety of aquatic invertebrates to different levels of UV-B. The simulator was calibrated as close as possible to match local ambient solar radiation measured in and out of water with a scanning spectroradiometer. A series of repeated exposures were conducted to determine the effects of UV-B on two species of Ceriodaphnia. Survivorship of C. reticulata declined with increasing UV-B with 100% mortality occurring after four daily 5 hr exposures to a UV-B irradiance that was 14% of ambient sunlight (40.8/μW/cm²) and 70% mortality for C. dubia after seven days of an exposure to 5% of ambient (14.5μW/cm²). Significant reductions in fertility (#young/adult) was observed in both low and high light adapted individuals with low light individuals appearing to be more sensitive. This methodology allowed us to make comparisons to natural conditions in aquatic habitats and to make risk assessments for individual species.