Microplastic contamination in clams (Meretrix meretrix) in the Bons Sinais Estuary

Microplastic pollution has become a growing concern in aquatic ecosystems due to its wide distribution and potential impacts on marine biodiversity. Bivalves, due to their filter-feeding habits, are widely used as bioindicators of environmental contamination. In this context, the present study aimed to evaluate the occurrence, abundance, and characteristics of microplastics in clams (Meretrix meretrix) collected in the Bons Sinais estuary, as well as to compare the abundance of these particles among different size classes of bivalves. Samples were collected manually during low tide and processed in the laboratory by alkaline digestion with 10% NaOH, followed by density separation with a saturated NaCl solution and filtration. Microplastics were quantified and classified according to shape, color, and size by observation under a stereoscopic magnifying glass. Statistical analyses were performed using R software. 150 individuals were analyzed, of which 90% presented microplastics. A total of 202 particles were identified, with an average abundance of 1.35 ± 0.82 PMs/individual. The particles were mostly fibers (up to 82.4%), black in color (up to 60.0%), and < 1.0 mm in size (up to 67.6%). No statistically significant differences were observed in microplastic abundance between juvenile and adult bivalves. The results indicate high and widespread microplastic contamination in the Bons Sinais estuary, highlighting the influence of local anthropogenic sources. These results reinforce the need for environmental management strategies and continuous monitoring to promote the sustainability of estuarine ecosystems and aquatic resources that underpin the Blue Economy in Mozambique