Microplastic contamination in no-take Marine Protected Areas of Brazil: Bivalves as sentinels

Microplastics (MPs) are pervasive environmental contaminants even in remote and pristine locations. Despite extensive literature documenting their widespread presence in marine environments, there is limited understanding of MP contamination in Marine Protected Areas (MPAs), particularly in developing countries. This study assessed MP contamination using multiple filter-feeding bivalve species as sentinels. Samplings were performed during 2022, in ten selected no-take MPAs under different management categories according to the International Union for Conservation of Nature. MPs size, shape, color, and polymeric composition were analyzed using established protocols, including Fourier Transform Infrared (FTIR) spectroscopy. MPs concentrations (0.42 ± 0.34 [0.17-2.00] particles.g ww) peaked at natural monuments, while strict nature reserves and parks were less affected. Based on scientific literature comparison, no-take MPAs were less contaminated by MPs than multiple-use MPAs and unprotected areas in Brazil. However, the observed levels remain concerning, given the potential ecological risks, including trophic transfer, physiological disruptions, and habitat degradation. Around 59% of MPs were organic polymers and alkyd (28%), while polyethylene terephthalate (14%) was the main anthropogenic polymer. MPs were predominantly black, white, or transparent fragments measuring <1000 μm, not differing among MPAs individually or grouped protection category, therefore displaying the consistent qualitative patterns along the Brazilian coast. This study underscores the ecological risks posed by MPs in MPAs, emphasizing the need for long-term monitoring programs and targeted mitigation strategies, contributing to global efforts assessing and managing MP contamination, aligning with the 11th Aichi Target to reduce pressures on biodiversity and promote marine ecosystems sustainable use.