Ingestion of plastic and non-plastic microfibers by farmed gilthead sea bream (Sparus aurata) and common carp (Cyprinus carpio) at different life stages

Environmental pollution by plastic particles is of major global concern, as a potential threat to aquatic organisms and ecosystems. The accumulation of microplastics in freshwater and marine environments has strong ecological implications due to their long persistence, potential toxicity, and ability to adsorb other pollutants, acting as vectors of pathogens. Nevertheless, while the number of studies on the presence of microplastics in the wild fish increased, less attention has been paid to the farmed fish species. Here, we investigated the occurrence of microparticles in the digestive tracts of Sparus aurata and Cyprinus carpio at different life stages and reared by an intensive and semi-intensive production system, respectively. Our results showed the presence of natural microfibers and microplastics, with microfibers (similar to 90%) being the dominant type. In both fish species, the presence of microparticles was not revealed at larval stage. Fry and adult S. aurata specimens showed microfiber abundances of 0.21 and 1.3 items/individual, respectively. A lower load of microparticles (p < 0.05) occurred in fry (0.06 items/individual) and adult C. carpio specimens (0.25 items/individual). As to the chemical composition of the micro-items, natural (20%), semi-synthetic (28%), and single or blended synthetic fibers (52%) were identified in S. aurata. Linen, rayon, lyocell, cotton: polyester and polyester (12.5% concentration for each polymer) fibers were identified in C. carpio, while PTFE (37.5%) was present as fragments. Rayon was the most frequent chemical type (21.2%). The polymer composition of the extracted microparticles showed significant differences between the fish species analysed (p < 0.05). Notably, a considerably lower contamination level of synthetic polymers (average 0.11 items/individual) was detected in the farmed fishes compared with the data obtained in other studies on feral ones. To the best of our knowledge, this is the first study reporting the plastic and the non-plastic microfiber contamination in the farmed S. aurata and C. carpio at different life stages.