Soil microbial communities play a crucial role in maintaining ecosystem health, driving key processes such as nutrient cycling, organic matter decomposition, and soil fertility. However, these microbial populations are highly sensitive to environmental changes and chemical stressors, including pesticides. The preprint "Evaluating the effects of environmental disturbances and pesticide mixtures on soil microbial endpoints," provides valuable insights into how soil microbial communities respond to environmental fluctuations and pesticide exposure (Drocco et al., 2025). By integrating experimental soil microcosms with targeted microbial assessments, the study offers a comprehensive view of the resilience and vulnerability of soil microbiota under multiple stress conditions.

The study aimed to assess how temperature and humidity fluctuations, along with pesticide exposure, impact soil microbial communities. A total of 250 soil microcosms were subjected to three different environmental conditions: heat disturbance, high humidity simulating heavy rain, or a control with no disturbance. Following a three-day recovery period, the microcosms were exposed to different pesticide active ingredients—clopyralid (herbicide), cypermethrin (insecticide), and pyraclostrobin (fungicide)—either individually or in combination at standard (1x) and elevated (10x) agronomic doses.

By evaluating microbial endpoints related to diversity and community structure, the researchers were able to determine how environmental disturbances and chemical exposure influence soil microbial functions (Bacmaga et al., 2015). Of particular interest was the focus on microbial guilds involved in nitrification, a critical process for soil nitrogen cycling and agricultural productivity (Dominati et al., 2010).

The study’s findings reveal a complex interplay between environmental stressors and pesticide exposure on microbial communities. Some key observations showed that heat and high humidity significantly altered microbial diversity and composition before pesticide application. This suggests that climate-driven disturbances can precondition microbial communities, potentially influencing their subsequent responses to chemical exposure. Moreover, the pesticide effects depend on dose and combination, while individual pesticides had measurable impacts on microbial endpoints, their effects were amplified when applied in mixtures or at elevated doses. This underscores the importance of considering real-world pesticide applications, where mixtures are commonly used. Furthermore, the results indicate that the microbial guilds involved in nitrification appeared to be disproportionately affected by pesticide exposure, raising concerns about long-term soil fertility and nitrogen availability in treated soils.

These findings have significant implications for sustainable agriculture and soil health management. Understanding how soil microbiota respond to environmental and chemical stressors can inform strategies to mitigate negative impacts, such as adopting precision agriculture techniques, improving pesticide formulations, and implementing soil conservation practices.

Despite its valuable contributions, the study has some limitations. The controlled microcosm approach, while useful for isolating specific variables, may not fully capture the complexity of field conditions. Long-term effects of pesticide exposure were also not assessed, leaving questions about microbial recovery and ecosystem stability over extended periods. Future research should focus on field-based experiments and long-term monitoring to validate and expand on these findings.

In conclusion, the current study highlights the intricate interactions between environmental stressors and pesticide exposure on soil microbial communities. By leveraging a robust experimental design and providing open-access data and statistical scripts, the research enhances our understanding of soil microbial dynamics and their implications for agricultural sustainability. As climate change and intensive pesticide use continue to shape soil ecosystems, such studies are essential for developing resilient and sustainable soil management practices.

References

Bacmaga, M., et al., 2015. Microbial and enzymatic activity of soil contaminated with a mixture of diflufenican + mesosulfuron-methyl + iodosulfuron-methyl-sodium. Environ Sci Pollut Res Int. 22: 643-56, https://doi.org/10.1007/s11356-014-3395-5 

Dominati, E., et al., 2010. A framework for classifying and quantifying the natural capital and ecosystem services of soils. Ecological Economics. 69: 1858-1868, https://doi.org/10.1016/j.ecolecon.2010.05.002 

Drocco, C., Coors, A., Devers-Lamrani, M., Martin-Laurent, F., Rouard, N., Spor A. 2025. Evaluating the Effects of Environmental Disturbances and Pesticide Mixtures on N-cycle related Soil Microbial Endpoints. ver.3 peer-reviewed and recommended by PCI Ecotoxicology and Environmental Chemistry, https://doi.org/10.1101/2024.01.22.576671

Fish is an essential component of healthy human diets and the preservation of fish stocks and other marine resources is included as a target of Sustainable Development Goal 14 ‘Conserve and sustainably use the Oceans, Sea and Marine Resources for Sustainable Development’ (UNEP). However, several fish stocks remain in sub-optimal (or worse) conditions due to overfishing and a range of stressors including chemical pollution. Chemical pollution can result in high level of chemicals in fish making it unsuitable for human consumption. Furthermore, the occurrence of chemical-related physiological stress in otherwise apparently healthy fish requires additional research efforts. In natural environments, further complexity arises from fish being simultaneously exposed to multiple contaminants/stressors as opposed to laboratory investigation usually dealing with one or very few contaminants/stressors at a time (Schäfer et al., 2023).

Beauvieux et al. (2024) examined the possible role of accumulation of multiple elements on the physiological status of first-year-of-life specimen of European sardine collected in the Gulf of Lions (northeastern Mediterranean Sea) as a contributing factor to the declining sardine population observed in the region since 2008. The ultimate objective of the paper was to identify potential biomarkers of stress in fish otherwise not exhibiting any anomalies in body condition, in agreement with the principles of chemical stress ecology put forward by van der Brink (2008). 

Out of a total of 105 specimen, individuals were selected according to the lowest (n = 14) or highest (n = 15) levels of contamination and subject to proteomic analysis of liver and red muscle tissues.  A first Principal component analysis on all specimen highlighted the possible influence of the Rhone river as a source of geogenic and anthropogenic elements to the Gulf of Lions. 

A second PCA performed only on specimen selected from proteomics analysis allowed to identify three elemental mixtures possibly responsible for the observed physiological effects. Proteomic analysis in liver and muscle tissue identified both similarities and differences in the pathways involved in response to stress. More in detail, the expression patterns of Myosin and Myomesin were downregulated in red muscle for highly exposed specimen, which suggests possible effects of elemental accumulation on the locomotion abilities of Mediterranean sardines. Pathways involved in lipid metabolism and immune processes were up-regulated in liver, pointing to increased energetic costs for maintaining the overall fish homeostasis in presence of metal contamination. It is interesting to note that these effects were observed at concentrations below the legal thresholds for human consumption (except for As), albeit such thresholds are available only for a limited number of elements (Cd, Pb, Cd, As and inorganic Sn) (EU, 2023).

Although stressors other than trace elements could contribute to the observed molecular responses, as acknowledged by the authors themselves, Beauvieux et al. (2024) show that biological responses at lower levels of biological organization can provide both early-warning indications of potential adverse effects in the long term and better understanding of drivers of population decline. By advancing our knowledge of the physiological responses to trace elements and identifying potential biomarkers, this study lays the groundwork for more effective monitoring and conservation strategies. Further studies addressing the combined effects of multiple environmental stressors remain essential to develop holistic approaches to marine ecosystem management and species conservation. 

References

Beauvieux A., Fromentin J.-M., Saraux C., Romero D., Couffin N., Brown A., Metral L., Bertile F., Schull Q. (2024). Molecular response to multiple trace element contamination of the European sardine. bioRxiv, ver. 4 peer-reviewed and recommended by Peer Community in Ecotoxicology and Environmental Chemistry. https://doi.org/10.1101/2024.02.16.580673  

EU (2023). Commission Regulation (EU) 2023/915. https://eur-lex.europa.eu/eli/reg/2023/915/oj/eng

Schäfer R. B., Jackson M., Juvigny-Khenafou N., Osakpolor S. E., Posthuma L., Schneeweiss A., Spaak J., & Vinebrooke R. (2023). Chemical Mixtures and Multiple Stressors: Same but Different? Environmental Toxicology and Chemistry, 42(9), 1915-1936, https://doi.org/10.1002/etc.5629

UNEP: https://sdgs.un.org/goals

Van den Brink P. J. (2008). Ecological Risk Assessment: From Book-Keeping to Chemical Stress Ecology. Environmental Science & Technology, 42(24), 8999-9004. https://doi.org/10.1021/es801991c