Combined effects of ultraviolet-B radiation and food shortage on the sensitivity of the Antarctic amphipod Paramoera walkeri to copper

Investigations on the combined effects of ultraviolet (UV)-B radiation and anthropogenic toxicants have focused primarily on the chemical interactions between UV-B and organic compounds. Only a few studies have examined wheth er exposure to UV-B changes sensitivity to toxicants. This question is addr essed in a laboratory study using the common shoreline Antarctic amphipod P aramoera walkeri and exposure to environmentally realistic levels of copper , UV-B radiation, and food shortage. Exposure to copper for 21 d in the abs ence of any additional stressors (food present, no UV-B) showed a lowest ob servable effective concentration (LOEC) of greater than 100 mug Cu/L. Expos ure to copper and UV-B in combination, with no shortage of food, resulted i n a LOEC of 45 mug Cu/L. When exposed to copper and UV-B, with shortage of food, a LOEC of 3 mug Cu/L was recorded. Hence, the combination of environm ental stress from exposure to UV-B radiation and shortage of food increases the sensitivity of P. walkeri to copper more than 30-fold. Increased metab olic energy requirements for defense mechanisms in response to toxicants an d UVB are discussed as possible explanations. It is concluded that consider ation of environmental stressors in combination with toxicants increases th e accuracy of ecological risk assessments of toxicants and should be part o f the process for developing guidelines for ecologically acceptable concent rations of contaminants in the environment.