Berlin Brandenburg Institute of Advanced Biodiversity Research

Abstract Microplastics are increasingly recognized as emerging contaminants in terrestrial ecosystems, yet their mechanistic impacts on soil multifunctionality remain poorly understood. Here, we evaluated the influence of two microplastic polymers, polyethylene terephthalate and polypropylene, on soil functioning by subjecting soils to a gradient of concentrations of these microplastics, and measuring six variables representing soil physical, chemical, and biological functions. A statistical framework combining multi-model inference with threshold detection and machine learning was implemented in this study to identify the main pathways of soil multifunctional change. Most significant responses followed nonlinear trends and threshold shifts, primarily in physical properties, indicating that microplastic stress first impacts soil structure before cascading to chemical and biological processes. We identified two system-level thresholds at 0.3% PP and 0.55% PET w/w; while random forest highlighted water-stable aggregates as the dominant predictor of overall soil multifunctionality. Our findings provide new quantitative evidence of complex soil multifunctionality responses to microplastic pollution. Most importantly, physical deterioration emerged as an early-warning signal of microplastic disturbance, thereby advancing our understanding of microplastic pollution on soil systems.

Micro- and nanoplastics have emerged as critical contaminants in aquatic ecosystems due to their small size, persistent nature, and potential for bioaccumulation. Nanoplastics are particularly concerning because they can be widespread in aquatic environments and ingested by aquatic organisms, posing potential risks to ecological health and environmental sustainability. However, the response and recovery of aquatic plants to nanoplastics, as well as the cell-specific molecular mechanisms underlying these processes, remain unclear. By integrating single-cell transcriptomics, enzymatic assays, and europium-doped nanoplastic tracing, we comprehensively investigated the response of duckweed to polystyrene nanoplastics at environmentally relevant and high doses over exposure and recovery phases. Nanoplastics exposure reduced plant reproduction and root length by inducing oxidative damage, with partial recovery after removal. Single-nucleus RNA sequencing revealed cell-type-specific responses of duckweed to nanoplastics, particularly in mesophyll, mestome sheath, epidermis, and parenchyma cells. Interestingly, recovery triggered a greater number of differentially expressed genes mechanistically linked to carbon metabolism, membrane transport, and stress-responsive pathways. Nanotracer quantification demonstrated root/frond absorption and 36.8-51.4% postrecovery excretion. These multiscale lines of evidence decipher the molecular strategies of duckweed to nanoplastics at single-cell resolution, providing mechanistic insights into the interactions between aquatic plants and nanoplastics contamination.

Extreme weather events intensify with global change and frequently disturb aquatic ecosystems via, e.g. nutrient pulses through surface runoff. While there is accumulating evidence that the associated short-term responses of plankton communities depend on their top-down control (TC), the actual shape of TC-community response relationships remains unclear. We therefore conducted 24 flow-through (chemostat) experiments to investigate algal and rotifer biomass responses to a nutrient pulse along a gradient of TC values. To generate this gradient, we used a trait-based method instead of varying the inoculation species densities. We complemented our analysis by estimating non-measured nutrient dynamics and feeding interactions via Bayesian modelling. We found support for hump-shaped relationships. At low TC, algal species were strongly nutrient-depleted, limiting their immediate growth potential after the pulse and thereby that of rotifer species. At high TC, algae were not nutrient-limited; thus, algae and rotifers hardly responded. At intermediate TC, responses were larger because algae immediately exploited the pulse, and rotifers exploited the increased algal biomass production without preventing an algal bloom. This study showed the importance of investigating community responses to resource pulses along a gradient of TC values, thereby improving the understanding of the ecological stability of food webs under global change.

Pesticides are a major anthropogenic input to the environment and a factor in global change that puts pressure on soil microbial communities. However, the effects of different rates of pesticide application on soils remain poorly understood. This study investigates how abrupt versus gradual pesticide applications influence soil bacterial and fungal communities. Employing high-throughput sequencing, we examined the microbial diversity and community composition in response to ten commonly used pesticides. Bacterial communities exhibited minimal changes across treatments, whereas fungal communities responded strongly to pesticide exposure. Gradual applications reduced the relative abundance of dominant fungal taxa, resulting in an overall increase in community evenness. This effect was particularly pronounced for two herbicides and a triazole fungicide, which induced substantial shifts in fungal composition. Conversely, abrupt pesticide applications resulted in transient disruptions but did not promote the long-term proliferation of rare fungal variants. These findings suggest that prolonged exposure to pesticides exerts strong selective pressures on fungi, potentially altering fundamental soil functions such as nutrient cycling and decomposition. Future research should focus on the long-term responses of soil microbial communities to pesticide application and the cumulative effects of chronic low-dose exposure to provide a more comprehensive understanding of how they shape microbial communities.

The turnover of dissolved organic matter (DOM) in soil regulated by biodegradable microplastics (MPs) has garnered much attention due to its profound impact on the storage and stability of soil organic matter. However, the transformation and reactivity of plant-derived and microbially derived DOM by microorganisms adapted to biodegradable MPs, and the involved microbial physiological processes, remain nearly unknown. Here, we added virgin and aged polylactic acid (PLA) and polyhydroxyalkanoate (PHA) to agricultural soils and incubated for 56 days. Using stable isotope techniques, reactomics, and metagenomics, we found that the addition of both virgin and aged PLA induced hydroxylation, demethylation, and dehydrogenation of lignin-derived DOM, resulting in a 3-fold increase in their oxidation degree. PLA activated the enzymatic pathway for lignin-derived DOM decomposition and downregulated genes involved in bacterial anabolism, such as those related to protein, amino sugar, and peptidoglycan biosynthesis. In contrast, PHA increased the content of microbially derived DOM compounds such as proteins and amino sugars by 2.1-fold relative to the control with peptide chain elongation. PHA resulted in the degradation of lignin-derived DOM into pyruvate and acetyl-CoA, accelerated bacterial ATP synthesis, the de novo biosynthesis of proteins and peptidoglycan, and cell renewal and death, thereby increasing PHA- and soil organic matter-derived microbial necromass carbon. Our study provides new insights into the impact of biodegradable MPs on soil DOM transformation and underscores the importance of the microbial physiological processes involved.

Abstract The influence of common mycorrhizal fungal networks (CMNs) on their components—namely the plants and the linking fungal genet—has been studied for decades and is under constant debate. Besides new research evidence on mechanisms and functionality of CMNs, the actual ecological importance of effects mediated by CMNs on the plant and fungal components is still understudied. Here, we conducted a meta‐analysis focusing on arbuscular mycorrhizal (AM) fungi as linking genets and evaluated the magnitude of effects mediated by CMNs on plant and fungal parameters. We found neutral or inconsistent effects for the tested plant and fungal parameters. The detected effects were small. The wide range of positive to negative CMN effects in our database indicates strong context dependence. In combination with data limitations for the different tested parameters, any attempts at general inferences must be done very carefully. Given the widespread lack of significant responses, it is very difficult to derive well‐supported conclusions about the meaning of the CMN for the biology of the fungi and the plants and the general ecological significance of the CMN. Thus, we call for a renewed research effort to strengthen the evidence base for effects mediated by CMNs on plant and fungal parameters. We recommend exercising caution when communicating to the public about effects mediated by CMNs formed by AM fungi. Read the free Plain Language Summary for this article on the Journal blog.

Conservation flagships are an effective approach to mobilize support for conservation. The flagship concept has recently been expanded beyond species, to include also fleets, protected areas, ecosystems, individuals, and events. Here, we present a unifying framework of flagship categories and their use, provide a roadmap for flagship selection, and give recommendations for their use in conservation practice. We also propose the flexible encompassing term ‘flagship entity’, broadly defined as a unique and recognizable entity that can be easily communicated for conservation purposes. Flagship entities are characterized by their biological and ecological organization level, temporal state, geographical reach, current level of use, and effectiveness. Flagship selection should be driven by sound knowledge and a clear understanding of the target audience’s conscious and subconscious preferences and its intended use. Further work is needed to evaluate the effectiveness of various flagship categories and concepts, and the positive and negative economic outcomes of flagship strategies. • The concept of conservation flagships has recently been expanded beyond species. • Flagships now also include fleets, protected areas, ecosystems, individuals, and events. • The presented flagship entity concept unifies existing flagship categories. • Flagships should be selected by the intended use and audience’s preferences. • Effectiveness of flagship entities should be carefully evaluated.

Harnessing root nitrogen reallocation (RNR) to enhance plant productivity commences with positioning RNR in the root economics space, about which we still know little. We conducted an inclusive synthesis linking RNR to root traits, combined with a 2-year 15N-labelling field experiment, to position RNR in the root economics space under acidification. RNR was negatively correlated with specific root length (SRL) and mycorrhizal colonisation in the synthesis, suggesting that RNR is a conservative trait. Sedges, grasses and forbs coordinated root traits (e.g., RD and SRL) from acquisitive to conservative and from low to high RNR reliance (and vice versa for their direct root N uptake) in the 15N-tracing experiment. Along the collaboration gradient, mycorrhizal symbiosis contributed more to N acquisition in grasses and forbs than in sedges, correlating inversely with SRL but remaining orthogonal to RD and RNR, thus partially reflecting the root economics space. Specifically, sedges and forbs exhibited the lowest and highest RNR that increased and decreased with acidification, respectively. Grasses associated well with mycorrhizal fungi, showing moderate RNR and root traits. Our results demonstrated the significance of RNR in plant growth, and the need to consider RNR as a conservative trait.