Pestizideffekte an den Rändern? Auswirkungen von agrochemischer Verschmutzung flussabwärts auf Organismen in Refugien
Hydrogeologie, Hydrologie, Limnologie, Siedlungswasserwirtschaft, Wasserchemie, Integrierte Wasserressourcen-Bewirtschaftung
Zusammenfassung der Projektergebnisse
Based on several studies in the last two decades, it is relatively well established that pesticides shape invertebrate assemblages in streams, with an increase in the relative abundance of tolerant taxa. Our understanding of the response and long-term consequences of toxicant effects is still deficient with respect to spatial dynamics and adaptation processes. Genetic adaptations to pesticides in terms of tolerance may propagate to non-polluted patches as shown in modelling studies. However, empirical studies on the potential of downstream effects of pesticide pollution to propagate to organisms in non-polluted upstream sections are scarce. In this project, we examined for different invertebrate species (a gammarid and a trichopteran) as well as for invertebrate assemblages to which extent pesticide effects can propagate to organisms or assemblages in refuges. We sampled stream water for pesticide analyses, invertebrate assemblages as well as gammarids and trichopterans, in agricultural sites with high pesticide toxicity and in refuges at two distances (edge of refuges and further upstream) in June 2019. The project benefited from a nationwide pesticide monitoring programme (Implementation of the national monitoring of small water bodies for pesticides) that provided high quality pesticide data, high resolution physicochemical data as well as assemblage data on invertebrates for the agricultural sites and one refuge site (whit the exception of the pesticide analysis, all of these sampling and analyses were carried out by the PhD student of the current project). In addition, we conducted the same analyses for all edge sites and the remaining refuge sites for the same period. Using acute toxicity tests, we determined the tolerance of the invertebrates. Moreover, we determined the genetic diversity and energy reserves in gammarids. We hypothesised the absence of pesticide exposure at edges and refuges and high pesticide exposure at agricultural sites. Based on previous studies, we hypothesised that pesticide exposure at agricultural sites results in adaptation processes measurable as i) a reduction in the relative abundance of pesticide-sensitive invertebrates (SPEARpesticides) and ii) increase of insecticide tolerance in invertebrates in acute toxicity tests. We further hypothesised that this adaptation reduces genetic diversity and that via dispersal this propagates to non-polluted patches at the edge of the refugium. Moreover, following the concept of resource allocation, we assumed that a higher tolerance is associated with higher allocation of energy to defence mechanisms, resulting in lower energy reserves compared to less tolerant organisms. In line with our hypotheses, pesticide exposure was higher and the proportion of pesticide-sensitive species (SPEARpesticides) was lower in agricultural sites compared to edge and refuge sites. Notwithstanding, at some edge and refuge sites, which were considered as being least impacted, we estimated unexpected pesticide toxicity (sum toxic units) exceeding thresholds where field studies suggested adverse effects on freshwater invertebrates. We conclude that organisms in forest sections within a few kilometres upstream of agricultural areas can be exposed to ecologically relevant pesticide levels. In addition, although not statistically significant, the abundance of pesticide-sensitive taxa was slightly lower in edge compared to refuge sites, indicating a potential influence of adjacent agriculture. In contrast to our hypothesis, the acute toxicity tests revealed a slightly higher insecticide sensitivity of organisms in agricultural sites. Genetic diversity and energy reserves were similar among refuge, edge and agricultural sites. The genetic distance between populations of the three site types within the same stream was low, suggesting high connectivity, considerable gene flow, and no pronounced differences among populations of refuge, edge and agricultural sites within each stream. Based on the results of other studies, we suspect that multiple stressors as well as short distance to refuges and constant exchange between site types lead to the absence of adaptative development and rather an increase in sensitivity. Overall, this research project advances our assessment of the costs of pollution for organisms and populations in non-polluted areas. Future studies should further investigate the influence of spatial relationships, such as the distance between refuge and agriculture, for the propagation of pesticide effects and focus on the underlying mechanisms.
Projektbezogene Publikationen (Auswahl)
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Potential propagation of agricultural pesticide exposure and effects to upstream sections in a biosphere reserve. Science of The Total Environment, 836, 155688.
Schneeweiss, Anke; Schreiner, Verena C.; Reemtsma, Thorsten; Liess, Matthias & Schäfer, Ralf B.
