Use of aquatic macrophyte field data in the higher tiers of the risk assessment for plant protection products in Europe.

This study presents a comprehensive dataset of aquatic macrophyte field observations aimed at supporting higher-tier risk assessments for plant protection products (PPPs). The dataset includes species composition and abiotic conditions of edge-of-field freshwater systems such as ponds, streams, and ditches across Europe and key functional traits of their most common macrophytes. Analysis showed that the key macrophyte species are broadly distributed and are already frequently included in Species Sensitivity Distributions (SSDs) as well as in mesocosm and potted plant studies. The data collected is useful in the context of pesticide risk assessment as it provides information on which species could be focal species and information to define ecological scenarios as well as to use in ecological models. Also the data can support a reference tier that enhances ecological realism in aquatic risk assessments. A case study using the herbicide metazachlor illustrates how the dataset can inform regulatory decision-making by comparing SSD-derived endpoints based on toxicity endpoints for macrophyte species found in edge-of-field surface waters with those from traditional mesocosm studies. This approach offers an alternative to experimental systems, aligning with current regulatory goals for more representative and efficient risk assessments.