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Microplastic in bivalves from the heavily contaminated Guanabara Bay, Rio de Janeiro, Brazil
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Scientists tested mussels and oysters from Guanabara Bay in Brazil—one of Latin America's most polluted waterways—and found some of the highest microplastic levels ever recorded in shellfish there, especially near cities and ports. Since these are the same types of shellfish people eat, this study is a reminder that seafood from polluted coastal waters may carry significant plastic contamination, though more research is needed to understand what that means for our health.
Microplastic contamination is pervasive in urbanized coastal ecosystems, and Guanabara Bay is an ecologically relevant coastal system under intense anthropogenic use in Brazil, ranking among the most polluted estuaries in Latin America. However, spatially resolved biomonitoring efforts remain scarce in this bay. Here, we assessed microplastic contamination using multi-species, multi-site approaches to determine spatial patterns and contextualize levels with previous cross-matrix studies conducted in the bay. Across fifteen sites sampled along gradients of urbanization and environmental conditions, 678 microplastics were detected in 280 individuals, averaging 2.4 and reaching 45.0 particles g -1 in mussels and oysters. Such values exceeded national levels, ranking among the highest reported for bivalves from Brazil and aligning with patterns related to previous cross-matrix studies in Guanabara Bay. The observed spatial gradient showed higher microplastic levels in the southern bay, near dense urban areas and port infrastructure, and lower concentrations in the eastern and northern sectors, which are surrounded by mangroves and protected areas. Despite differences in habitat use and filtration rates, microplastic concentrations did not differ significantly among species, which equally reflected spatial gradients, indicating comparable sentinel performance. This consistency among suspension-feeding species indicates comparable signals of spatial contamination, supporting their use as complementary sentinels. Fibers dominated the ingested microplastics, which were predominantly small-sized, transparent particles composed mainly of natural and anthropogenic cellulose. These findings demonstrate widespread microplastic contamination in Guanabara Bay and support the use of multiple species as robust sentinels for assessing microplastic exposure in coastal systems.
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Researchers assessed microplastic contamination in clams collected from extensive coastal regions of southern Brazil. They found microplastics in the soft tissues of clams across all sampling sites, with contamination levels influenced by proximity to urban areas, rivers, and local water flow patterns. The study highlights that even organisms in less urbanized coastal areas are accumulating microplastics, raising concerns about widespread contamination in shellfish habitats.
Microplastic in bivalves of an urbanized Brazilian estuary: Human modification, population density and vegetation influence
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Researchers measured microplastic contamination in oysters, clams, and mussels from a heavily urbanized estuary in Brazil, finding that industrial and port activities were stronger predictors of contamination than population density. Clams accumulated the most microplastics, and the study highlights how shellfish from polluted coastal areas can serve as indicators of the microplastic levels humans may be exposed to through seafood.
Oysters and mussels as equivalent sentinels of microplastics and natural particles in coastal environments
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Researchers compared how oysters and mussels accumulate microplastics in a polluted Brazilian estuary and found both species performed equally well as biological monitors of contamination. Some of the highest microplastic levels ever recorded in shellfish were found at the most polluted sites. Since oysters and mussels are widely consumed as seafood, these contamination levels raise direct concerns about human microplastic exposure through shellfish consumption.
Microplastic contamination in the mangroves of Piraquê-Açu and Piraquê-Mirim rivers, Aracruz (Brazil): An analysis in sediment, water, and biota
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Researchers found widespread microplastic contamination in a Brazilian mangrove ecosystem, detecting over 7,800 particles across water, sediment, and two species of shellfish consumed by local communities. Oysters contained higher microplastic levels than mussels, and sediments served as the main collection point for the particles. Since these shellfish are an important food source, the contamination represents a direct pathway for human microplastic ingestion.
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