Environmentally Derived Nanoplastics Induce Oxidative and Genotoxic Responses in Gilthead Seabream (Sparus aurata)

Marine environments are becoming increasingly contaminated by plastic debris that degrades into nanosized particles, posing an emerging risk to aquatic organisms. However, few studies have examined the biological effects of nanoplastics (NPs) derived from real environmental sources rather than laboratory-grade materials. Therefore, this study aimed to obtain NPs from plastic pellets collected from the environment and assess their effects on the marine fish Gilthead seabream ( Sparus aurata ). Plastic pellets collected from La Pineda Beach (Tarragona, NE Spain) were characterized using Attenuated Total Reflectance Infrared (ATR-FTIR) spectroscopy. The pellets were then used to produce NPs by mechanical abrasion, chemical dispersion, and sonication. Particles were characterized by transmission electron microscopy, showing heterogeneous, irregular particles of less than 500 nm. Dynamic Light Scattering (DLS) indicated an average hydrodynamic diameter of 154.6 ± 54.6 nm, while Nanoparticle Tracking Analysis (NTA) revealed most particles ranged in size from 25–300 nm. A 96-hour exposure bioassay to the obtained NPs was done with seabream (Sparus aurata) as a model species (control and 1 mg/L NPs; n=10 fish per group), resulting in 100% survival with no significant differences in growth indices (p>0.05). However, NPs exposure significantly increased red blood cell count (p=0.0488) and reduced thrombocyte count (p=0.001). Erythrocytic nuclear abnormalities (ENAs) were also higher (p=0.018), especially for lobed (p=0.018) and segmented nuclei (p=0.035), which indicates genotoxicity. Liver gene expression analysis showed upregulation of cat (p=0.003), gpx1 (p=0.044), sod (p=0.036), and pparβ (p<0.001), reflecting oxidative stress and altered lipid metabolism. This study is the first to demonstrate that NPs generated from environmental pellets induce oxidative and genotoxic responses in S. aurata , revealing their sublethal toxicity and ecological relevance in marine and aquaculture systems. • Environmentally sourced plastic pellets were converted into heterogeneous nanoplastics (25–300 nm). • Short-term exposure (1 mg/L) in gilthead seabream altered RBC and platelet profiles. • Nanoplastics triggered genotoxicity through increased erythrocytic nuclear abnormalities. • Oxidative stress was evidenced by upregulated antioxidant and metabolism-related genes.