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Section: Ecotoxicology & Environmental Chemistry ; Topics: Agricultural sciences, Environmental sciences, Microbiology

Evaluating the effects of environmental disturbances and pesticide mixtures on N-cycle related soil microbial endpoints

Drocco, Camilla; Coors, Anja; Devers, Marion; Martin-Laurent, Fabrice; Rouard, Nadine; Spor, Ayme

10.24072/pcjournal.537 - Peer Community Journal, Volume 5 (2025), article no. e33.
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Pesticides are widely used in conventional agriculture, either applied separately or incombination during the culture cycle. Due to their occurrence and persistence in soils, pesticideresidues may have an impact on soil microbial communities and on supported ecosystemservices. In this regard, the EFSA (European Food Safety Authority) recently published ascientific opinion inciting to change pesticide risk assessment to better protect soil microbe-mediated processes. Climate change is another major concern for all living organisms includingsoil microbial community stability. Extreme climatic events, such as heat waves or heavyrainfalls, are becoming more and more frequent and their impact on soil microbial diversity andfunctions have already been demonstrated.The objectives of this study were to evaluate the effects of temperature and humiditydisturbances and pesticide active ingredients exposure on soil microbial community structureand functions. To this end, 250 soil microcosms were exposed to either a heat disturbance, ahigh humidity to mimic heavy rain, or no environmental disturbance. After three days ofrecovery, soil microcosms were treated with different active ingredients: clopyralid (herbicide),cypermethrin (insecticide) and pyraclostrobin (fungicide). The treatments were applied aloneor in combination at 1x or 10x of the agronomical dose. We then evaluated the effects of thedisturbances and the active ingredients on various microbial endpoints related to the diversityand the structure of soil microbial communities, and with a specific focus on microbial guildsinvolved in nitrification.Overall, we demonstrated that the impact of environmental disturbances applied to soilmicrocosms, especially heat, on microbial endpoints was stronger than that of the activeingredients applied alone or in combinations. Compounded effects of environmentaldisturbances and active ingredients were detected, but sparsely and were of small scale for thechosen pesticides and applied doses.
Section: Ecology ; Topics: Ecology, Population biology

Delayed dichromatism in waterfowl as a convenient tool for assessing vital rates

Tableau, Adrien; Henderson, Iain; Reeber, Sébastien; Guillemain, Matthieu; Maillard, Jean-François; Caizergues, Alain

10.24072/pcjournal.531 - Peer Community Journal, Volume 5 (2025), article no. e32.
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Monitoring the number of individuals is by far the most popular strategy for studying the environmental factors that determine population dynamics and for measuring the effectiveness of management actions aimed at population recovery, control or eradication. Unfortunately, population size monitoring is inefficient in identifying the mechanisms underlying demographic processes and, in particular, in assessing the extent to which population growth rate is influenced by changes in adult survival rather than variations in reproductive parameters. In many waterfowl species, sexual dichromatism is observed in adults, while immatures of both sexes display a plumage pattern similar to that of adult females. In these species, the apparent proportion of males increases as the female-like immature males gradually take on the plumage of adult males. The difference between the apparent sex ratio before and after the young reach sexual maturity then provides information about the age ratio of a population. Using winter counts that distinguished between female-like and male-like individuals of two non-native populations of Ruddy duck Oxyura jamaicensis, a species that exhibits such a plumage pattern, we present a non-invasive method based on the apparent sex ratio to split population growth rate into adult survival and recruitment rates (the latter also referred to as productivity). This method can correctly detect annual changes in vital rates, supporting the assumption that counts conducted in an appropriate time window reflect the age structure of a population. We exemplify how the respective contributions of survival and productivity to the population growth rate are essential for understanding the processes behind demographic dynamics. Finally, we point out some best practices to correctly apply the ``apparent sex ratio'' method described here.
Section: Ecology ; Topics: Agricultural sciences, Ecology, Microbiology

Mineral fertilization reduces the drought resistance of soil multifunctionality in a mountain grassland system through plant-soil interactions

Piton, Gabin; Foulquier, Arnaud; Bernard, Lionel; Bonin, Aurelie; Pommier, Thomas; Lavorel, Sandra; Geremia, Roberto; Clement, Jean Christophe

10.24072/pcjournal.534 - Peer Community Journal, Volume 5 (2025), article no. e31.
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Increasing droughts threaten soil microbial communities and the multiple functions they control in agricultural soils. These soils are often fertilized with mineral nutrients, but it remains unclear how this fertilization may alter the capacity of soil multifunctionality (SMF) to be maintained under drought, and how plant-soil interactions shape these effects. In this study, we used a mountain grassland soil to test the interactive effect of mineral nutrient (Nitrogen and Phosphorous) addition and drought on SMF with and without plants (Lolium perenne) in a mesocosm experiment. We calculated SMF based on 8 microbial properties associated with the capacity of soil microbes to store carbon (C), nitrogen (N) and phosphorous (P) in their biomass, and to process these elements through organic matter depolymerization, mineralization, nitrification and denitrification processes. To investigate mechanisms underlying the SMF response we characterized the associated changes in soil stoichiometry and microbial community composition using 16S and 18S rRNA amplicon sequencing. Our results showed that fertilization decreased the SMF drought resistance when plants were present, but the opposite was observed in the unplanted mountain grassland soil. Our analysis suggested this was due to the interaction of plants, fertilization and drought in influencing four coupled properties related to high SMF: high soil moisture, low microbial C limitation, high bacterial diversity and low bacteria gram positive:gram negative ratio. Altogether, our results suggested that reducing the use of mineral fertilizer for plant production in mountain grassland could improve the ability of their soils to maintain their multifunctionality during drought period. Finally, our study clearly further demonstrated the importance of plant in the complex responses of SMF to global changes and showed that combining stoichiometric and microbial diversity assessment represents a powerful approach to disentangle the underlying mechanisms.
Section: Microbiology ; Topics: Ecology, Microbiology, Statistics

Factors shaping vaginal microbiota long-term community dynamics in young adult women

Kamiya, Tsukushi; Tessandier, Nicolas; Elie, Baptiste; Bernat, Claire; Boué, Vanina; Grasset, Sophie; Groc, Soraya; Rahmoun, Massilva; Selinger, Christian; Humphrys, Michael S.; Bonneau, Marine; Graf, Christelle; Foulongne, Vinccent; Reynes, Jacques; Tribout, Vincent; Segondy, Michel; Boulle, Nathalie; Ravel, Jacques; Lía Murall, Carmen; Alizon, Samuel

10.24072/pcjournal.527 - Peer Community Journal, Volume 5 (2025), article no. e30.
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The vaginal microbiota is known to affect women's health. Yet, there is a notable paucity of high-resolution follow-up studies lasting several months, which would be required to interrogate the long-term dynamics and associations with demographic and behavioural covariates. Here, we present a high-resolution longitudinal cohort study of 125 women, followed for a median duration of 8.6 months, with a median of 11 samples collected per woman. Using a hierarchical Bayesian Markov model, we characterised the patterns of vaginal microbiota community persistence and transition, simultaneously estimated the impact of 16 covariates and quantified individual variability among women. We showed that “optimal” (Community State Type (CST) I, II, and V) and “sub-optimal” (CST III) communities are more stable over time than “non-optimal” (CST IV) ones. Furthermore, we found that some covariates — most notably alcohol consumption — impacted the probability of shifting from one CST to another. We performed counterfactual simulations to confirm that alterations of key covariates, such as alcohol consumption, could shape the prevalence of different microbiota communities in the population. Finally, our analyses indicated that there is a relatively canalised pathway leading to the deterioration of vaginal microbiota communities, whereas the paths to recovery can be highly individualised among women. In addition to providing one of the first insights into vaginal microbiota dynamics over a year, our study showcases a novel application of a hierarchical Bayesian Markov model to clinical cohort data with many covariates. Our findings pave the way for an improved mechanistic understanding of microbial dynamics in the vaginal environment and the development of novel preventative and therapeutic strategies to improve vaginal health.

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The network image was drawn by Martin Grandjean: A force-based network visualization CC BY-SA