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.

Traits and stress: keys to identify community effects of low levels of toxicants in test systems

“…For example, in test systems, abiotic stressors such as high temperature (Fisher and Wadleigh 1985; Song et al 1997; Lydy et al 1999) and a deficiency of food (Pieters et al 2005) were found to increase the sensitivity of macroinvertebrates to insecticides by a factor of from 2 to 10. UV radiation in conjunction with food deficiency increased sensitivity to copper by a factor of more than 30 (Liess et al 2001). In addition, biotic stressors such as competition (Liess 2002; Beketov and Liess 2005) and predation pressure (Schulz and Dabrowski 2001; Beketov and Liess 2006) increased vulnerability to toxicants.…”

“…Inversely, the occurrence of traits of species in a given habitat can be used to infer environmental characteristics. To identify the effects of agricultural pesticides on field communities this approach was first developed by Liess and co-workers (Liess et al 2001) and later elaborated within the Species At Risk concept (SPEAR) (Liess and von der Ohe 2005). The SPEAR bioindicator system was validated to identify non-point pesticide contamination (Schäfer et al 2007) and point sources of toxicants originating from treatment plants (Ashauer, in revision).…”

“…Hence, to determine the quantitative link between exposure and effect it is necessary to consider additional stress factors. Such factors include a wide range of stressors that increase the rate of mortality due to toxicants (factor of increase in brackets): exalted temperature (10) (Song et al 1997), food limitation (2) (Pieters et al 2005), exalted salinity (10) (Wildgust and Jones 1998), low oxygen (2) (Van der Geest et al 2002), UV radiation (30) (Liess et al 2001), competition (10) (Liess 2002), predation (8) (Beketov and Liess 2006), and the requirement of food acquisition (10) (Mommaerts et al 2010). …”

Predicting the synergy of multiple stress effects

“…Since then, increasing evidence has suggested that the impacts of multiple stressors of different types may synergistically exceed the effects of individual stressors, as has been demonstrated for a range of organisms 8 . Examples include (i) wild bee populations and honey bee colonies, which have declined in response to the combined effects of pesticides and environmental stressors, such as parasites 9 , reduced floral abundance or weather 8 10 ; (ii) marine crustaceans, which have exhibited an increased sensitivity to the combination of copper and ultraviolet radiation 11 ; (iii) amphibians, which have been negatively affected by the interaction between agrochemicals and parasites 12 ; and (iv) human populations, for which heat stress exacerbates the toxicity of many air pollutants, insecticides, and other toxic chemicals 13 .…”

The pros and cons of ecological risk assessment based on data from different levels of biological organization

“…These “context dependencies” result in a range of sensitivities for a given species across a range of conditions that could include intra- or inter-specific competitors, predators, food availability, temperature, pH, disease, etc. In fact, abiotic stressors can increase toxicant sensitivity up to 30 fold in some population and community test systems (Liess and Beketov 2011, Liess et al 2001). Importantly, responses over a gradient or combination of different contexts are infrequently monotonic or linear and are frequently difficult to predict.…”