Addressing inaccuracies in predicting ecological risk of pesticide : influence of environmental factors and long-term detriment at sublethal concentrations

Russo, Renato; Ließ, Matthias Erwin Fritz (Thesis advisor); Hollert, Henner (Thesis advisor)

Aachen : RWTH Aachen University (2021, 2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021


Although prior their market authorization pesticides undergo a tiered regulatory framework to predict the associated ecological risk, their application continue to threat the integrity of precious freshwater environment worldwide. Obviously, the current ecological risk assessment framework, which predicts pesticides effects mostly based on laboratory standard tests, is not protective enough. The present thesis addressed some of the factors that are not integrated in the current risk assessment framework and therefore contribute to magnify the effects pesticides in the field beyond predictions. In particular, this research focused on: (i) exploring biomolecular changes, by means of metabolomic techniques, to identify those metabolites that, in freshwater invertebrates, can be altered after exposure to pesticides and therefore can be potentially used as early screening tool of detrimental effects, whose phenotypical manifestation is commonly delayed (Chapter 3). (ii) comparing, through laboratory toxicity tests, the sensitivity of organisms under different conditions or of different populations under same conditions. The data obtained were used to implement models that enabled a thorough analysis of the influence of various environmental factors on the sensitivity of nontarget invertebrates, the effect of repeated exposures and the evolution of resistance to pesticides (Chapter 2, Chapter 4).(iii) assessing directly in the field the dynamic of populations exposed to pesticides. The selected sampling sites covered a wide range of combinations of factors, such as pesticide pressure, season of sampling, species diversity, distance from non-polluted stream sections. Such conditions ensured an in-depth analysis of the influence of each variable on the abundance and the evolution of resistance of freshwater invertebrates (Chapter 2, Chapter 4).The results of this research showed that:(i) concentration of pesticides far below the regulatory acceptable concentrations caused metabolic changes in exposed freshwater species. Such changes reflected an increased energy demand that can potentially translate into reduced fitness, explaining the phenotypically delayed adverse effects that are frequently observed in freshwater invertebrate communities exposed to sublethal level of pesticides in agricultural streams (Chapter 3). (ii) the toxicity of pesticides toward freshwater crustaceans was magnified by the interaction with natural stressors (Chapter 2, Chapter 4), namely temperature stress and high intraspecific competition. Additionally, in the field repeated exposure to pesticides increased the sensitivity of freshwater invertebrates when the following exposure occurred within one generation (Chapter 2). (iii) various environmental factors influenced the evolution of resistance in freshwater invertebrates. Specifically, resistance was governed mainly by the level of pollution, but also significantly by seasonal variation, availability of non-polluted refuge sections, and species diversity (Chapter 4). In conclusion, these outcomes might be used to refine the predictive power of laboratory-based standard tests. Knowledge on delayed effects of sublethal concentrations of pesticides and on the influence of environmental factors in magnifying pesticide effects in the wild should be included in the regulatory procedures to make the current risk assessment framework more protective for freshwater ecosystems and the precious services they provide.