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Environmental variations and toxicological responses

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... The most striking result of the present study was the statistically significant increase in variation of population response parameters of selected taxa in the treatment mesocosms compared to the controls ( Table 2, Fig. 2). On the one hand, variation in species responses has always been a big issue in ecotoxicology and species tests [51][52][53], as it hinders the statistical evaluation of true effects from background noise with regard to mean values. On the other hand, there is increasing evidence that interreplicate variation of population development parameters as a result of genotype plasticity of individuals, can be an indicative endpoint for chemical pollution [54]. ...
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Background Several large-scale studies revealed impacts and risks for aquatic communities of small rural lakes and streams due to pesticides in agricultural landscapes. It appears that pesticide risk assessment based on single products does not offer sufficient protection for non-target organisms, which are exposed repeatedly to pesticide mixtures in the environment. Therefore, a comprehensive stream mesocosm study was conducted in order to investigate the potential effects of a realistic spraying sequence for conventional orchard farmed apples on a stream community using pesticides at their regulatory acceptable concentrations (RACs). Eight 74-m-long stream mesocosms were established with water, sand, sediment, macrophytes, plankton and benthic macroinvertebrates. In total, nine fungicidal, four herbicidal and four insecticidal pesticides were applied in four of the eight stream mesocosms on 19 spraying event days in the period from April to July while the remaining four stream mesocosms served as controls. The community composition, the abundance of benthos, periphyton and macrophytes, the emergence of insects, physico-chemical water parameters, and drift measurements of aquatic invertebrates were measured. Results The pesticide spraying sequence induced significant effects on invertebrates, periphyton, and macrophytes as well as on the water ion composition especially in the second half of the experiment. It was not possible to relate the observed effects on the community to specific pesticides applied at certain time points and their associated toxic pressure using the toxic unit approach. The most striking result was the statistically significant increase in variation of population response parameters of some taxa in the treated mesocosms compared to the controls. This inter-individual variation can be seen as a general disturbance measure for the ecosystem. Conclusions The pesticide spraying sequence simulated by using RAC values had notable effects on the aquatic stream community in the conducted mesocosm study. The results indicate that the current risk assessment for pesticides may not ensure a sufficient level of protection to the field communities facing multiple pesticide entries due to spraying sequences and other combined stress. Hence, there is still room for improvement regarding the prospective risk assessment of pesticides to further reduce negative effects on the environment.
... For example pollution has become a global issue with increasing pollution of the open ocean (Jackson, 2010). Nikinmaa and Tjeerdema (2013) recently suggested that changes in UV-R could affect the responses of sea surface organisms to pollutants and modify the structure of potential toxicants, an area worthy of further investigation. ...
... They are generally considered through the angle of confounders that could mask the effect of contaminant and lead to false evaluation of population and ecosystem health. They could be abiotic factors of natural (temperature, salinity…) or anthropogenic origin (contamination, but also pH, organic matter…) or biotic factors such species interaction, food availability, parasitism (Beketov and Liess, 2008;Beketov et al., 2011;Knillmann et al., 2013;Minguez et al., 2012;Nikinmaa and Tjeerdema, 2013). ...
... Understanding and predicting the effects of contaminants in environmental systems experiencing multiple stresses is a central question in ecotoxicology (Artigas et al., 2012). Contaminant bioavailability and effects could change with the variations of different environmental factors (Nikinmaa and Tjeerdema, 2013). Three different cases can be considered when an environmental factor acts in combination with contaminants (Fischer et al., 2013): (i) the organisms are well adapted to environmental conditions, which do not represent a stress for the organism and there is no interference with contaminant toxicity; (ii) the changes in environmental factors induce alterations in the organism physiology, thus the acclimation to the new condition confers tolerance to specific contaminant; (iii) the environmental conditions represent a stress to the organism, and when contaminants and the environmental factors interfere, antagonistic, synergistic or additive effects can be observed. ...
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Toxicological responses of an organism are disturbances of function. This as a starting point we review and discuss issues that we consider important in applying functional genomics to aquatic toxicology. Functional genomics includes all the steps in gene expression pathway. Thus, ultimately the goal is to relate genome information to protein activity. In ecotoxicogenomics the toxicological responses must further be combined with responses to natural environmental changes. We focus on fish, but also consider commonly used invertebrates, mainly Daphnia. We first go through the toxicologically important features of genomes of aquatic animals, and then review the reference gene approach to quantify transcript amount. Thereafter we emphasize the need to relate the mRNA and protein levels, and protein activity of individual genes. Finally we discuss how functional genomic investigations may be important in resolving current environmental problems and give our views of valuable future research topics.
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