Microplastics (MPs) are concerning and persistent pollutants in aquatic environments, capable of adsorbing contaminants and affecting organisms through bioaccumulation. In aquaculture, they can originate from both external (e.g., atmospheric deposition, water source) and internal sources (e.g., food, plastic equipment, and wear of components) . This study investigated the presence and characteristics of MPs in the water from a recirculating aquaculture system (RAS) used for tilapia farming. The system included nine tanks with and nine without plastic cover, housing three strains of tilapia and fed with both commercial feeds and the macrophyte Lemna . Ten liters of water were collected from each tank at the start and end of the 90-day production cycle, filtered using 68µm mesh, digested with 35% hydrogen peroxide (H₂O₂) at 60 ºC for 48 hours, and vacuum filtered using Whatman GF/F filters. MPs above or equal 68µm were visually analyzed u nder a stereomicroscope coupled with a digital camera and the ImageView software for morphology , color, and size characterization.
Preliminary r esults from six water samples from each treatment indicated no significant statistic difference between the number of MP found in the covered and the uncovered area ( t = 1.63 , p = 0.134). There was also no significant difference in the size distribution of microplastics between treatments , according to the Mann-Whitney U test ( U = 2.24.10⁶, p = 0.60). The predominant particle size class was 100–200 µm; f ibers were the most frequently observed morphological type and transparent was the most observed color in both treatments.
These findings suggest that neither the quantity nor the characteristics of microplastics in the water were significantly influenced by the presence of a plastic tank cover. The values obtained fall within the range reported in the literature for aquaculture systems, although they are slightly higher than those typically observed in recirculating systems. This difference may be attributed to the more intensive management practices involved, particularly the use of multiple feed sources (commercial feeds and Lemna).