Polylactic acid microplastics (PLA-MPs) are ubiquitous environmental contaminants that can act as carriers for antibiotics such as azithromycin (AZI). However, the manner in which PLA-MPs shape modulates antibiotic-induced disruption of the gut microbiota remains poorly understood. In this study, we evaluated the intestinal toxicity of four PLA-MPs shapes—film, fiber, particle, and sphere—all of which were co-exposed with AZI at 1 and 10 mg/L in zebrafish (Danio rerio). Biochemical analysis showed that the combined exposure to particle PLA-MPs at 10 mg/L AZI (Particle_10AZI) induced the most severe oxidative stress and digestive dysfunction. Co-exposure also caused locomotor hyperactivity and reduced anxiety-like behavior, with the strongest effects observed in the Particle_10AZI group. Histopathological analysis suggested that combined exposure to sphere PLA-MPs at 10 mg/L AZI (Sphere_10AZI) induced pronounced intestinal atrophy, whereas Particle_10AZI elicited a mixed response involving both tissue compensation and injury. PLA-MP shape further determined distinct patterns of gut microbial disruption: combined exposure to film PLA-MPs at 10 mg/L AZI (Film_10AZI) and Particle_10AZI reduced both richness and diversity, whereas the combined exposure of fiber PLA-MPs at 10 mg/L AZI (Fiber_10AZI) and Sphere_10AZI reduced richness and increased diversity. Particle_10AZI induced the most severe dysbiosis, characterized by enrichment of Pseudomonadota (particularly Gemmobacter) and depletion of Bacteroidota (particularly Flavobacterium). Metabolomic profiling further confirmed shape-dependent metabolic disturbances. Correlation analysis revealed that pro-inflammatory Pseudomonadota were positively associated with elevated AZI levels and a pro-fibrotic metabolite, whereas beneficial Bacteroidota were associated with the anti-inflammatory metabolite docosahexaenoic acid. Collectively, these findings suggested that AZI could determine the overall direction of toxicity, whereas PLA-MP shape was linked to the intensity and specificity of toxic effects, potentially through the gut microbiota–metabolite axis. This study highlights the importance of incorporating MP shape in toxicity assessments and wastewater management strategies.
Recurrent heatwaves can induce physiological carry-over effects, but how inter-heatwave intervals influence photosynthesis, oxidative stress, and photochemical performance in trees remains poorly understood. We investigated two subtropical tree species, Schima superba and Phoebe bournei, exposed to a single heatwave or two heatwaves separated by intervals of 7, 15, or 23 days. Leaf gas exchange, chlorophyll fluorescence, antioxidant enzyme activities, and malondialdehyde (MDA) content were measured at a common final sampling date. Under the shortest inter-heatwave interval, net photosynthetic rate declined by 50.8
Popillia japonica is an invasive beetle first detected in Northern Italy in 2014 and considered as one of the most dangerous pests for crops due to the economic, environmental, and social costs by European phytosanitary authorities. Here we develop a process-based model for quantifying the invasion dynamics of P. japonica with the goal to elaborate risk maps for the design of surveillance and control strategies. The proposed spatially heterogeneous model captures the different behaviors of both adults, which drive the invasion through flight and short-distance human-mediated transport, and ovo-larval stages, which affect demography due to their susceptibility to environmental conditions. Both processes are biologically informed through variables that are known to influence population dynamics, namely the number of summer days, affecting the flight ability of the adults, and the environmental suitability for larval survival. The simulated presence of adult beetles is then contrasted to pest observation data at the municipality scale from Northern Italy and Switzerland from the initial invasion to December 2023. Results reveal that the ongoing outbreak is occurring in one of the most favorable areas for the beetle, the Po Valley, which favors rapid spread and can sustain high population densities. Mountain regions emerge as obstacles to the progression of the invasion, with the Alps, excluding the valleys, being an almost insurmountable defense, whereas the Apennines only slow down the southward advancement without stopping it altogether. The projected speed of invasion, within and outside the outbreak area, ranges between 0 and almost 20 km/year and it is modulated by environmental conditions. The predicted speed of invasion at continental level constitutes an actionable tool for invasion management, since it provides phytosanitary services with a critical evidence base for optimizing the geometry and extent of delimitation and containment areas.
Increasing vapor pressure deficit (VPD) alters ecosystem carbon and water exchange, but agroecosystem water use efficiency (WUE) may respond nonlinearly to rising atmospheric evaporative demand. The VPD levels at which these nonlinear transitions occur, their spatial consistency, and the factors associated with spatial variation in breakpoint magnitude remain poorly understood. We therefore examined nonlinear WUE responses to increasing VPD and assessed how breakpoint magnitude varied across croplands in relation to environmental and agricultural characteristics. Using multisource observations from 111 sub-basins of the Songhua River Basin during 2002–2024 and independent eddy covariance observations from cropland sites, we identified a nonlinear WUE–VPD relationship. The first derivative of the generalized additive model fit indicated a point of maximum WUE sensitivity to VPD at approximately 0.27 kPa, whereas piecewise linear fitting identified the primary basin-scale breakpoint at approximately 0.41 kPa. Repeated subsampling indicated that the basin-scale breakpoint was robust to sampling variation, while local breakpoint estimates varied across sub-basins. Statistically supported breakpoints were detected in 59 of the 111 sub-basins, and site-level screening retained breakpoint estimates for 20 of the 28 evaluated cropland flux sites. The mean breakpoint estimate across the 20 retained flux sites was approximately 0.43 kPa. Sub-basin breakpoint magnitude was negatively associated with leaf area index, soil bulk density, and mean growing-season precipitation total, and positively associated with C4 crop proportion. Above the basin-scale breakpoint, the sensitivity of gross primary productivity to VPD increased significantly, whereas the sensitivity of evapotranspiration showed no significant change, indicating an asymmetric carbon–water response. At the retained flux sites, higher Bowen ratios and lower evaporative fractions above the site-specific breakpoints were consistent with a relative shift in energy partitioning toward sensible heat. The approximately 0.41-kPa breakpoint characterizes the basin-scale WUE response to increasing VPD but does not represent a universal local threshold. Spatial variation in breakpoint magnitude was associated with climate, vegetation structure, soil properties, and crop composition, although the observational design precludes direct causal attribution to individual management factors. These findings clarify spatial variation in nonlinear agroecosystem WUE responses to increasing VPD and underscore the importance of local environmental context when interpreting carbon–water responses to atmospheric drying.
As climate change accelerates, ecologically fragile regions are increasingly exposed to compound extremes. Agricultural intensification may perturb land–atmosphere feedback processes and exacerbate drought–heatwave coupling, yet the land-use thresholds governing non-linear risk amplification remain poorly constrained. This study focuses on a representative area in the agro-pastoral ecotone of northern China, the Horqin Sandy Land Ecological Conservation Area, to quantify cultivated-land-proportion thresholds for compound drought and heatwave onset. A space-for-time substitution was applied to 50 grid cells across five land-use patterns (cultivated land: 6.4
