Assessing the effect of microplastics on marine invertebrates: the consequence of exposure of sea urchin larvae to polystyrene microplastics

Polystyrene (PS) microplastics (PSMPs) represent a pervasive environmental pollutant in marine ecosystems, originating from the fragmentation of widely used, non-biodegradable plastic materials such as disposable plates. Despite growing concern over their ecological impacts, the mechanistic understanding of PSMP toxicity during critical early developmental stages remains limited. Here, we employed the sea urchin Paracentrotus lividus , a well-established model organism in marine ecotoxicology due to its sensitivity to environmental stressors, to investigate the effects of PSMPs derived from commercial disposable plates on fertilization, early embryogenesis, and larval development. We assessed morphological malformations, alterations in gene expression profiles related to detoxification, skeletogenesis, development, and stress responses, as well as embryo resilience to physical stress. Our results demonstrated that PSMP exposure induced significant developmental malformations and downregulation of multiple gene networks critical for normal development. Notably, the toxicity was dose- and time-dependent, with smaller particles and higher concentrations exerting more pronounced effects. Importantly, we observed that embryos retained the capacity for physiological recovery following PSMP removal, indicating a reversible toxic effect under certain conditions. These findings provided novel insights into the molecular and developmental pathways affected by PSMPs, revealing complex interactions between particle properties and biological responses. The study underlined the substantial risks posed by PSMP contamination to marine invertebrate early life stages, with potential cascading consequences for population dynamics and ecosystem health. Our work highlighted the urgent need for improved management of plastic waste and further mechanistic research to inform conservation strategies aimed at mitigating microplastic pollution in marine environments.