Combined Effects of Ultraviolet-B Radiation and Food Shortage on the Sensitivity of the Antarctic Amphipod Paramoera Walkeri to Copper

Abstract

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 whether exposure to UV-B changes sensitivity to toxicants. This question is addressed in a laboratory study using the common shoreline Antarctic amphipod Paramoera walkeri and exposure to environmentally realistic levels of copper, UV-B radiation, and food shortage. Exposure to copper for 21 d in the absence of any additional stressors (food present, no UV-B) showed a lowest observable effective concentration (LOEC) of greater than 100 microg Cu/L. Exposure to copper and UV-B in combination, with no shortage of food, resulted in a LOEC of 45 microg Cu/L. When exposed to copper and UV-B, with shortage of food, a LOEC of 3 microg Cu/L was recorded. Hence, the combination of environmental stress from exposure to UV-B radiation and shortage of food increases the sensitivity of P. walkeri to copper more than 30-fold. Increased metabolic energy requirements for defense mechanisms in response to toxicants and UV-B are discussed as possible explanations. It is concluded that consideration of environmental stressors in combination with toxicants increases the accuracy of ecological risk assessments of toxicants and should be part of the process for developing guidelines for ecologically acceptable concentrations of contaminants in the environment.

Increased sensitivity of the macroinvertebrate Paramorea walkeri to heavy-metal contamination in the presence of solar UV radiation in Antarctic shoreline waters

“…Interactive effects of UV-B and copper in the green alga Chlorella vulgaris result in a synergistic inhibition of photosynthetic activity, nutrient (except NH 4 + ) uptake, and enzyme activities (Rai & Rai 1997). Exposure to UV-B increases the sensitivity of a macroinvertebrate species (the amphipod Paramorea walkeri) to copper, and the resulting lowest-observedeffect concentration was > 30-fold increased in the presence of UV (Liess et al 2001). The results of the present study are thus in line with the information provided in the cited laboratory studies.…”

“…Indeed, UV-activation of polycyclic aromatic hydrocarbons (PAHs) and other contaminants has been reported recently (Nikkilä et al 1999), but UV would not be expected to affect the chemical form of heavy metals in a way that could have major effects on their toxicity. There is no information on combined effects of UV and heavy metals on aquatic animals apart from our recent study performed under laboratory conditions, which revealed an increased sensitivity of Paramorea walkeri to copper (Liess et al 2001). The relevance of those findings to the field conditions described here was tested in an outdoor test system.…”

“…For example, the sensitivity of aquatic organisms to contaminants such as heavy metals can be increased in the presence of ultraviolet (UV) radiation. This was shown in laboratory studies using a variety of organisms such as algae, rotifers and invertebrates (Rai & Rai 1997, Preston et al 1999, Liess et al 2001.…”

“…The possibility is suggested by a study showing that exposure to UV-B in the laboratory increases sensitivity of amphipods to copper (Liess et al 2001). The current investigation is based on a case study which involves (1) the characterization of contamination with heavy metals due to runoff from an old waste disposal site and of their ecological impacts, and (2) the response of organisms exposed to the combined parameters -solar UV radiation and heavy metals released in the field -using in situ bioassay, an outdoor test system and a field survey.…”

Toxic Effects of Contaminants in Polar Marine Environments

“…The combined effects of copper and other stressors, such as UV-B radiation and food shortage, increased the sensitivity of a common epontic-in-thewinter and shoreline-in-the-summer amphipods in the laboratory (39). Under natural conditions, these Fourteen-day exposures were needed to provide toxicity data comparable to 4-day exposures with temperate organisms.…”