Interactive effects of xenobiotic, abiotic and biotic stressors on Daphnia pulex--results from a multiple stressor experiment with a fractional multifactorial design.

Pollutant effects on aquatic key species are confounded by multiple abiotic and biotic stressors. To better discriminate and understand the intrinsic and environmental correlates of changing aquatic ecosystems, we untangle in present study how the effects of a low-dosed fungicide on daphnids (via different exposure routes) becomes modified by increasing temperature and the presence of a predator. Using a fractional multifactorial test design, the individual growth, reproduction and population growth rate of Daphnia pulex were investigated under exposure to the fungicide pyrimethanil at an environmental relevant concentration--either directly (via the water phase), indirectly (via food), dually (via water and food) or for multiple generations (fungicide treated source population)--at three temperatures and in presence/absence of the predator kairomones of Chaoborus flavicans. Our results clearly illustrate that multiple stress factors can modify the response of an aquatic key species to pollutants. The environmentally relevant exposure of the contaminant via food or the medium is of same importance. Nevertheless, temperature and the presence of a predator are the dominant factors controlling the reproduction of D. pulex. We conclude that sublethal pyrimethanil pollution can disturb the zooplankton community at suboptimal temperature conditions, but the effects will become masked by low temperatures or if chaoborid larvae are present.

Life stage-specific effects of the fungicide pyrimethanil and temperature on the snail Physella acuta (Draparnaud, 1805) disclose the pitfalls for the aquatic risk assessment under global climate change.

It can be suggested that the combined stress of pesticide pollution and suboptimal temperature influences the sensitivity of life stages of aquatic invertebrates differently. The embryo, juvenile, half- and full-life-cycle toxicity tests performed with the snail Physella acuta at different concentrations (0.06-0.5 or 1.0 mg L(-1)) of the model fungicide pyrimethanil at 15, 20 and 25 °C revealed, that pyrimethanil caused concentration-dependent effects at all test temperatures. Interestingly, the ecotoxicity of pyrimethanil was higher at lower (suboptimal) temperature for embryo hatching and F(1) reproduction, but its ecotoxicity for juvenile growth and F(0) reproduction increased with increasing temperature. The life-stage specific temperature-dependent ecotoxicity of pyrimethanil and the high fungicide susceptibility of the invasive snail clearly demonstrate the complexity of pesticide-temperature interactions and the challenge to draw conclusions for the risk of pesticides under the impact of global climate change.

Aquatic ecotoxicity of the fungicide pyrimethanil: effect profile under optimal and thermal stress conditions.

The aquatic ecotoxic profile of the fungicide pyrimethanil and its acute and chronic thermal dependence in two aquatic invertebrates Chironomus riparius and Daphnia magna were investigated. The ecotoxicity of pyrimethanil at optimal thermal conditions did not depend on the trophic level, but was species-specific. The acute pyrimethanil-toxicity on C. riparius increased with higher temperature. The chronic response of Daphnia magna to the NOEC of the fungicide was examined in a multigenerational experiment under three near-natural temperature regimes. A pyrimethanil-induced increase of total mortality was buffered by the strongly related increase of the general reproductive capacity, while population growth was stronger influenced by temperature than by the fungicide. At a LOEC, however, a second generation could not be established with D. magna at all thermal regimes. This clearly shows that thermal and multigenerational effects should be considered when appraising the ecotoxicity of pesticides and assessing their future risk for the environment.

Simulated climate change conditions unveil the toxic potential of the fungicide pyrimethanil on the midge Chironomus riparius: a multigeneration experiment.

Although it has been suggested that temperature increase may alter the toxic potential of environmental pollutants, few studies have investigated the potential risk of chemical stressors for wildlife under Global Climate Change (GCC) impact. We applied a bifactorial multigeneration study in order to test if GCC conditions alter the effects of low pesticide concentrations on life history and genetic diversity of the aquatic model organism Chironomus riparius. Experimental populations of the species were chronically exposed to a low concentration of the fungicide pyrimethanil (half of the no-observed-adverse-effect concentration: NOAEC/2) under two dynamic present-day temperature simulations (11.0-22.7°C; 14.0-25.2°C) and one future scenario (16.5-28.1°C). During the 140-day multigeneration study, survival, emergence, reproduction, population growth, and genetic diversity of C. riparius were analyzed. Our results reveal that high temperature and pyrimethanil act synergistically on the midge C. riparius. In simulated present-day scenarios, a NOAEC/2 of pyrimethanil as derived from a life-cycle toxicity test provoked only slight-to-moderate beneficial or adverse effects on C. riparius. In contrast, exposure to a NOAEC/2 concentration of pyrimethanil at a thermal situation likely for a summer under GCC conditions uncovered adverse effects on mortality and population growth rate. In addition, genetic diversity was considerably reduced by pyrimethanil in the future scenario, but only slightly under current climatic conditions. Our multigeneration study under near-natural (climatic) conditions indicates that not only the impact of climate change, but also low concentrations of pesticides may pose a reasonable risk for aquatic insects in future.

Acute and chronic toxicity of benzotriazoles to aquatic organisms.

PURPOSE: Resulting from their intensive use as corrosion inhibitors in aircraft deicing and anti-icing fluids (ADAF) and for silver protection in dishwasher detergents benzotriazoles (BTs) are widespread in European surface waters. The current study aimed on an ecotoxicological characterization of 1H-benzotriazole (1H-BT) and 5-methyl-1H-benzotriazole (5MBT). METHODS: Acute and chronic OECD guideline tests were conducted with primary producers (Desmodesmus subspicatus, Lemna minor) and two daphnia species (Daphnia magna, Daphnia galeata) to characterize the hazard of these chemicals. Additionally, the estrogenic activity of both BTs was analyzed in vitro using a recombinant yeast estrogen screen (YES). RESULTS: Both BTs revealed significant effects in acute and chronic experiments, but exhibited no estrogenic activity in the YES. The algal growth test displayed an inhibited cell number increase with effect concentration (EC) values of EC(10) 1.18 and 2.86 mg l(-1) for 1H-BT and 5MBT, respectively. In the Lemna test, EC(10) values were 3.94 mg l(-1) (1H-BT) and 2.11 mg l(-1) (5MBT). D. magna was also affected with EC(50) (48 h) values of 107 mg l(-1) for 1H-BT and 51.6 mg l(-1) for 5MBT. D. galeata was more sensitive with an EC(50) (48 h) of 14.7 mg 1H-BT l(-1) and 8.13 mg 5MBT l(-1). In the 21-day reproduction tests with D. magna, the EC(10) for 5MBT was 5.93 mg l(-1) while 1H-BT showed no adverse effects. D. galeata turned out to be more sensitive in the chronic study with EC(10) values of 0.97 mg l(-1) for 1H-BT and 0.40 mg l(-1) for 5 MBT. CONCLUSION: Because BTs are regularly found in the aquatic environment at lower µg l(-1) concentrations reflecting their persistence and poor elimination during wastewater treatment processes, a preliminary risk assessment was conducted. There is little indication that BTs pose a risk for aquatic ecosystems at current exposure levels during most of the year. However, it cannot be excluded that in winter with a higher usage of ADAFs environmental concentrations may well exceed the level that is considered safe for aquatic organisms.