Impact of polystyrene nanoplastics on early life stages of marine invertebrates: current knowledge and future research perspectives

Nanoplastics (<1 μm) are emerging pollutants with potential adverse effects on marine organisms, particularly during sensitive early life stages such as embryos and larvae. Marine invertebrates are key targets of nanoparticles toxicity and suitable models for assessing developmental impacts, yet their embryonic and larval stages remain understudied. This review synthesizes current knowledge on the embryotoxic effects of nanoplastics in marine invertebrates, focusing on studies using polystyrene nanoparticles (PS NPs) across diverse taxa including Rotifera, Mollusca, Arthropoda, Echinodermata, and invertebrate Chordates. Toxicity of PS NPs depends on surface functionalization, with amino-modified PS-NH2 generally more harmful than unmodified or carboxylated PS-COOH. Reported effects include oxidative stress, neurotoxicity, impaired fertilization in mollusks, skeletal defects in echinoderms, and altered behavior in crustaceans. Among tested models, ascidians emerge as particularly promising due to their phylogenetic proximity to vertebrates and compliance with EU legislation (Directive, 2010/63/EU), positioning them as ethically and scientifically valuable alternatives for developmental toxicity studies. Despite growing awareness, the current body of literature is constrained by a limited range of particle types, simplified exposure scenarios, and a focus on a few model organisms. To improve ecological relevance, future research should prioritize the use of environmentally realistic concentrations, diversify polymer types beyond PS, and include early life stages of ecologically important but underrepresented marine invertebrates. This will be essential to better understand the real-world impact of nanoplastics on marine ecosystems and to support more effective environmental risk assessment and regulatory frameworks.