An integrated review of glyphosate ecotoxicity and environmental fate in aquatic systems using species sensitivity distributions and meta-analysis.

The intensive global application of glyphosate has led to widespread contamination of aquatic environments, raising significant concerns for non-target organisms. This review systematically synthesizes and quantifies the environmental fate of glyphosate in aquatic systems, encompassing its transport, degradation, bioaccumulation, and ecotoxicological effects across various species. A distinctive feature of our analysis is the integration of meta-analysis and species sensitivity distribution (SSD) modeling to quantitatively derive toxicity thresholds and identify the most sensitive taxonomic groups. Meta-analysis of acute toxicity data reveals a distinct, concentration-dependent hierarchy of sensitivity (aquatic plants > fish > invertebrates > amphibians), which aligns with the plant-targeted mode of action of herbicide. SSD-derived chronic hazard concentrations (HC5) fall within the sub-milligram-per-liter range and indicate that invertebrates can exhibit equal or greater long-term sensitivity compared to aquatic plants. The primary toxic mechanisms are identified as oxidative stress, enzymatic inhibition, and endocrine disruption, culminating in neurological, developmental, and reproductive impairments across taxa. Commercial formulations are consistently shown to be significantly more toxic than glyphosate alone, and it is attributed to surfactant co-formulants. Furthermore, environmental factors such as pH, temperature, and water hardness are identified as key modulators of toxicity and environmental behavior of glyphosate. Critical knowledge gaps persist, particularly concerning the chronic effects of low-level exposures, the combined toxicity of mixtures of glyphosate and other complex pollutants, and its transformation and migration dynamics at the sediment-water interface. Addressing these uncertainties is paramount for refining ecological risk assessment frameworks and developing effective management strategies to mitigate the impacts of glyphosate in aquatic ecosystems.