Document: GAB-3-74-17

Survival and reproduction in the presence of UV radiation: A matter of repair?

DEE, G.* ¹, C.E.WILLIAMSON ¹ and D.KARAPELOU ²

Lehigh University, Bethlehem, PA 18015, USA ¹
Cedar Crest College, Allentown, PA, USA ²

Abstract:
A reduction in stratospheric ozone and subsequent increase in the amount of ultraviolet radiation (UVR) reaching the earth has been documented over north and south temperate regions. Many laboratory studies have focused on the effects of UVR on organismal survival and reproduction. In order to extrapolate UV effects from the lab to nature, the assumption of reciprocity must be met. Reciprocity is only satisfied when the effect of a total radiation exposure (dose) is independent of the time over which the exposure occurred (dose rate). The ability of organisms to undergo repair in the presence of light is thought to be a confounding factor in studies where reciprocity fails. This laboratory study explicitly tests whether reciprocity holds in two freshwater invertebrates with differing proficiencies of repair: A Cladoceran (Daphnia) which has been shown to have high repair, and a rotifer (Asplanchna) which is thought to have little to no repair. We found significant repair and a failure of reciprocity when comparing survival at different dose rates for both species. However, in a higher dose experiment with Asplanchna, we found no significant repair, and reciprocity held. These experiments show that there is a link between repair and reciprocity when survival data are used. Conversely, the ability of both Daphnia and Asplanchna to produce offspring after being exposed to UVR did not vary with dose rate. Reciprocity held in all cases. The capability to directly extrapolate the effects of UVR in the lab to its effects in nature depends not only on an organism's repair processes, but also on whether data is gathered on the organism's survival or reproduction.

Keywords: UV radiation, reciprocity, photorepair, zooplankton, reproduction, survival

This abstract is being presented at: 9:30 AM in session:
Oral Session #54: Lake Ecology.