Quantifizierung des Biodiversitätsverlustes und Konvergenz der Reaktion von ökologischen Merkmalen bei Pestizidexposition in landwirtschaftlichen Gebieten
Zusammenfassung der Projektergebnisse
Pesticides represent an important stressor for ecosystems in agricultural landscapes. Despite their relevance, a comparatively low amount of studies has examined the effects of pesticides in real world ecosystems. The assessment of field effects of pesticides in streams and riparian areas is hampered by the fact that pesticides usually co-occur with other stressors such as elevated nutrient concentrations and suspended sediment inputs. To disentangle the effect of pesticides on stream and riparian ecosystems from that of other stressors, we conducted a field study in Romania, where low-intensity agriculture persists in rural areas besides regions with high-intensity agriculture. Streams adjacent to fields with low-intensity agriculture receive inputs of sediments and nutrients, whereas pesticide input can be considered minimal. Overall, the main objectives of the project were (a) to examine whether the trait composition of communities in adjacent ecosystems and ecosystem functioning in terms of leaf decomposition converges in response to pesticide stress and (b) to improve the quantification of pesticide effects in stream ecosystems. After the project was granted, we were able to establish a cooperation that yielded to a more comprehensive pesticide monitoring. In addition, we expanded the riparian sampling to terrestrial predators in terms of spiders as well as to their aquatic and terrestrial prey. This allows to extend the analysis for potential trait changes from beetles and aquatic invertebrates to spiders and to quantify the contribution of aquatic and terrestrial prey to the spider diet. Given that one PI changed institutions and that the pesticide analysis took considerably longer than planned, here we only report preliminary findings and more advanced data analyses including such that integrate data sets (e.g. structural equation models) are underway. We analyzed 246 pesticides and their metabolites and detected 88 pesticides and metabolites. The calculated pesticide toxicity gradient spanned approximately 3 orders of magnitude and was not associated with a proxy for agricultural intensity or % of agricultural land use within the catchment or riparian zone. The pesticide toxicity was a major predictor for macroinvertebrate community composition. The community composition was largely unresponsive to nutrients, whereas habitat structure (riffles), flow and temperature were additional determinants of the community composition. Three of four stress biomarkers determined in gammarids varied significantly among sites. No association of parasitism by microsporidians, nematodes and trematodes with pesticide toxicity was found for gammarids and mayflies (Baetis sp.). In the riparian zone, we found 832 ground beetle individuals of 86 different taxa. The communities were mainly influenced by land use-related gradients of grain size in the stream and by vegetation structure at stream margins. Highly-structured surrounding landscapes favoured the occurrence of wing-less beetle species. Pesticide toxicity in the edge-of-field samples and studied streams, expressed as pesticide toxicity, showed a negative association with carabid species richness. Beside beetles, we collected and identified 3508 individuals of spiders and assigned them to 138 species. The trait composition of spider communities did not respond to pesticide toxicity, the total number of individuals exhibited a low correlation. However, species richness decreased with increasing pesticide toxicity. We also analysed the proportion of aquatic prey in the diet using stable carbon and nitrogen isotopes. Pardosa consumed between 26 and 59% aquatic insects and Tetragnatha between 24 and 64%. Generally, with increasing stressors and agricultural intensity less aquatic prey was consumed by both spiders. Whereas pesticide toxicity was not associated with the proportion of consumed aquatic prey by Tetragnatha, the proportion of aquatic diet intake for Pardosa increased with toxicity. Only one of the four biomarkers in spiders showed significant differences across sites. No association of parasitism by microsporidians, nematodes and trematodes with pesticide toxicity was found for spiders. Regarding functional responses, preliminary analyses, from which pesticide toxicity and terrestrial leaf breakdown data were omitted due to a lack of data at time of analysis, showed that the % of agricultural land use in the catchment was among the most important predictors for fungal biomass and macroinvertebrate-mediated leaf litter breakdown. Overall, preliminary analyses suggest that pesticide toxicity shaped aquatic and terrestrial communities and their predators. Conclusions regarding trait changes and functional responses are too premature.
Projektbezogene Publikationen (Auswahl)
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Influence of agricultural land use on aquatic-terrestrial predator prey relationships in Romania. Symposium for European Freshwater Sciences 2017, held 2 July – 7 July 2017, 2017, Olomouc, Czeck Republic
Graf, N.; Entling, M.H.; Frisch, K.; Schreiner, V. C.; Szöcs, E.; Schäfer, R. B.
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Influence of agricultural land use on riparian spider communities in Romania. SETAC GLB 2017, held 12 November – 14 November, 2017 in Neustadt, Germany
Graf, N.; Dittrich, P.; Entling, M.H.; Schreiner, V. C.; Schäfer, R. B.
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Influence of agriculture related stressors on aquatic-terrestrial predator-prey relationships in Romania. SETAC GLB 2017, held 12 November – 14 November, 2017 in Neustadt, Germany
Frisch, K.; Graf, N.; Schreiner, V. C.; Szöcs, E.; Entling, M. H.; Schäfer, R. B.
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Pesticide loads across an agricultural gradient in Romanian streams. SETAC GLB 2017, held 13 November – 15 November, 2017 in Neustadt, Germany
Schreiner, V. C.; Kunz, S.; Szöcs, E.; Vogler, B.; Beck, B.; Battes, K. P.; Cimpean, M.; Vermeissen, E. L. M.; Singer, H.; Hollender, J.; Ralf B. Schäfer, R. B.
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(2018): Einfluss von Landnutzung und Wasserqualität auf die Laufkäferfauna in aquatisch-terrestrischen Übergangsstrukturen Siebenbürgens (Rumänien). Jahrestagung der Gesellschaft für Angewandte Carabidologie (GAC). 16.-18.2.2018, Freckenhorst, Germany
Buse, J. and Schmidt, S.
