Understanding the impact of microplastics (MPs, plastic particles < 5 mm) on aquaculture species has become a growing concern in food safety worldwide . Indeed, MP occurrence has been reported not only in many wild-caught fish species but also in their farmed counterparts  . The interdependence between aquaculture production systems and reservoir environments, and their specificities related to plastic gear usage are likely to affect MP availability for uptake by fish  . Under the ‘One Health’ perspective, this work aimed to evaluate the MP occurrence in European seabass (Dicentrarchus labrax) produced in three different aquaculture systems by analysing water, fish feed and seabass tissue samples. Trace and non-essential metals in seabass muscle were also determined. H uman dietary exposure and toxicological risk from consuming farmed seabass muscle were estimated using Eur opean Food and Safety Authority (EFSA) recommendations.
Materials and methods
Approximately 50 specimens were collected from each of the three selected aquaculture systems : a cage farm located in Turkey , and a pond farm and a recirculating aquaculture system (RAS) both located in Portugal. Particles suspected of being made of plastic were quantified in the gastrointestinal tract (GIT) and muscle and visually characterized according to their shape, colour, and size. The chemical identification was performed through Fourier Transform Infrared Spectroscopy (FTIR).
The concentration of trace (Cr, Ni, Cu, Zn) and non-essential (Cd, Hg, Pb) metals in the seabass muscle were determined through Atomic Absorption Spectrophotometry (AAS).
H uman exposure to contaminants through seabass consumption was estimated based on European Market Observatory for Fisheries and Aquaculture Products (EUMOFA) data.
Comparatively h igher MP levels were detected in RAS water and feed than in the other systems (Fig. 1A and 1B). MPs with blue and black colour, fibre-shaped, and made out of cellulose/rayon and polyester, were the most common in all systems. MP characteristics were generally similar among fish tissues. C age-farmed seabass had the lowest MP occurrence, with 89% of the fish having at least one MP recovered from a certain tissue. At the tissue level, RAS-farmed fish had the highest MP levels in muscle , while in GIT, the values were also higher in these fish but comparable to those observed in pond-farmed seabass (Fig. 1C).
Cr, Ni, Zn, Cd, and Hg concentrations detected in muscle were all below the maximum permissible concentrations established for this species. Cu and Pb were below detection limits . No significant differences were observed among systems, except for Zn with pond-farmed seabass displaying the highest value (5.5 ± 0.7 vs. 3.6-4.6 µg/g w et weight).
Based on the available health-based guidance values (HBGVs) provided by EFSA for metals and considering a 150 g meal of seabass fillet, no toxicological risk associated with farmed seabass fillet consumption was observed. A monthly human exposure to MPs ranging from 1.8-9.3 per kg of consumer’s body weight was estimated, depending on seabass consumption habits in each country.
Our findings indicate that water and feed are t he primary pathways of MP exposure for farmed European seabass , which may potentially result in their retention in fish tissues . The presence of MP in muscle tissue indicates their potential availability to human consumers along with other environmental contaminants. However , the calculated human dietary exposure scenarios revealed low toxicological risks associated with consum ing seabass produced from the three analysed production systems. Despite the findings , the controlled conditions in artificial systems such as RAS are more likely to provide bet ter opportunities for minimizing M P contamination through the implementation of mitigation strategies (e.g ., development of natural system components) in the systems . This work is in line with the One Health concept, which acknowledges the interdependence of human, animal, and environmental health.
W ork funded by the project NORTE-01-0145-FEDER-000040. Financial support from the Portuguese Foundation for Science and Technology (FCT) through the grant awarded to R.M. (2022.10421.BD ) and L.G.A.B. (CEEIND/2020/02573). Also, CIIMAR is awarded by the Strategic Funding UIDB/04423/2020 and UIDP/04423/2020 through national funds provided by FCT and ERDF.
 Garrido Gamarro , E., Constanzo, V. (2022) Microplastics in food commodities - A food s afety review on human exposure through dietary sources . Food Saf. Qual. Ser. FAO, Rome, Italy.
 Sequeira, I.F., et al. 2020. Worldwide contamination of fish with microplastics: A brief global overview. Mar. Pollut. Bull. 160, 111681.
[ 3] Chen, G., et al. 2021. Occurrence and ecological impact of microplastics in aquaculture ecosystems. Chemosphere 274, 129989 .