Pioneering ecotoxicity tools: focused on soil microbiota, capturing multilevel effects
Healthy soils are essential for providing safe and healthy food, achieving climate neutrality, reversing biodiversity loss and halting desertification and land degradation. With the support of the Marie Skłodowska-Curie Actions programme(opens in new window), the ARISTO(opens in new window) project trained a new generation of scientists in multi-tier-level assessment of pesticide toxicity on the soil microbiome, and developed tools and guidelines to support these efforts.
Analytical and computational tools target pesticide toxicity
ARISTO project coordinator Dimitrios Karpouzas of the University of Thessaly(opens in new window) notes: “Microbes are essential for ecosystem functioning. Amongst them ammonia-oxidising microorganisms and arbuscular mycorrhizal fungi have a pivotal role in agricultural soil fertility and are sensitive to chemical stressors like pesticides. In addition, we have good tools to measure their population and activity in soils and plants.” ARISTO developed single species high-throughput in vitro tests to assess pesticide toxicity in these microorganisms. “The Organisation for Economic Co-operation and Development (OECD) is considering standardisation of our single species test for ammonia oxidisers,” says Karpouzas. The project went beyond conventional single-organism or single microbial group assessments to ecosystem level assessment of pesticide toxicity. “The paradigm considers both direct and indirect effects of pesticides and effects that can be measured across trophic levels in the soil food web,” Karpouzas adds. A new in silico tool can predict the transformation products of pesticide compounds in soil and identify chemical components in these that can trigger toxicity on soil microbes using ammonia-oxidising bacteria as proxies. Its use as an early screening tool during pesticide development could support commercialisation of compounds with minimal effects on soil microbiota.
Promoting soil science and public engagement
Thanks to application of ARISTO’s tests and tools, researchers found that the indirect effects of pesticides on soil microbiota are often more pronounced than the direct effects. Furthermore, the ‘OECD 216’ nitrogen mineralisation test currently used to assess the toxicity of agrochemicals on soil microbiota at regulatory level lacks sensitivity. It could be improved using higher resolution tools like those developed by ARISTO. Additionally, “outcomes support using data from single species tests and amplicon sequencing (a high resolution approach to identify the organisms in the soil microbiota community) in deriving ecotoxicity threshold values for risk assessment. This would revolutionise the assessment of pesticide toxicity on soil microorganisms,” emphasises Karpouzas. Finally, ARISTO’s training network not only gained scientific insight but shared it. The doctoral students visited elementary and high schools in Greece and Switzerland, where they addressed pupils’ enthusiastic questions about the importance of soil microorganisms and the nature of international research.
EU-level uptake supporting safer pesticides and soil health
The project’s outcomes could not be timelier. The European Food Safety Authority(opens in new window) is planning a revision of the terrestrial ecotoxicology guidance document and soil microbiota will be one of the focal points, considering direct and indirect effects. “ARISTO has delivered a scheme ready for uptake by policymakers complemented with tools, methods, guidelines and knowledge to support it. Uptake will revolutionise the current EU pesticide regulatory framework,” Karpouzas summarises. ARISTO’s doctoral students are already accepting jobs in industry and academia, ready to support implementation for safer pesticides and healthier soils.
