Thesis Title

The Effects of Ultraviolet-B Radiation on Aquatic Invertebrates

Date of Graduation

Spring 1996

Degree

Master of Science in Biology

Department

Biology

Committee Chair

John Havel

Subject Categories

Biology

Abstract

There is strong evidence that decreases in stratospheric ozone have led to increased ultraviolet-B radiation at the surface of the Earth. However, surprisingly little is known about the effects of UV-B radiation on aquatic ecosystems. The purpose of this study was to assess the sensitivity of aquatic invertebrates to UV-B radiation. Solar simulators were used to expose five species of aquatic invertebrates to enhance levels of UV-B radiation. The simulators were calibrated to match local ambient solar radiation. UV-B measurements in a eutrophic pond revealed that 90% of the irradiance was extinguished at approximately 30 cm depth. The irradiance at the upper 5-20 centimeters was comparable to levels used in the simulators. Median lethal dose (LD₅₀) values were determined for the cladocerans Ceriodaphnia reticulata, Scapholeberis kingii, and Daphnia magna, the ostracod Cyprinotus incongruens, and the amphipod Hyalella azteca. Among the species, 96-h LD₅₀ estimates were quite variable, ranging from 4.2 to 84.0 μW/cm². These estimates indicated S. kingii to be highly sensitive, H. azteca, C. reticulata, and D. magna moderately sensitive, whereas the ostracod C. incongruens was very tolerant to UV radiation. A survey of the distribution of S. kingii in Missouri ponds indicated that lightly pigmented individuals were restricted to turbid habitats, a finding consistent with the observation that light morphs could be induced at low light levels in culture. The sensitivity of both morphs to UV-B radiation was surprisingly similar. Overall, this study suggests that, in shallow ponds without physical refuges, UV-B radiation would have the strongest effects upon cladocerans and amphipods occuring in the water column, whereas ostracods would be better protected.

Copyright

© Robin D Hurtubise

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