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Despite being considered sanctuaries for biodiversity, Brazil's marine protected areas (MPAs) are not immune to microplastic contamination.

A recent study has shown that even MPAs classified as integral protection areas (APIs), which are the most restrictive to human intervention, are contaminated by this material. The research, which involved Brazilian and Australian scientists, used bivalve mollusks (oysters and mussels) as sentinel organisms to assess contamination. The results are in the journal Environmental Research.

"Our study showed that microplastic contamination occurs even in the most restrictive environmental protection areas; for example, in Atol das Rocas, where there's no economic activity and tourists aren't allowed to visit. Microplastics can reach places like this by being carried by the wind or ocean currents," 脥talo Braga, coordinator of the research and professor at the Institute of Marine Science of the Federal University of S茫o Paulo (IMar-UNIFESP) in Brazil, says.

Microplastics are particles ranging in size from 1 micron (1 渭m) to 5 millimeters (5 mm) that result from the fragmentation of larger plastics or are directly manufactured in this format for industrial or cosmetic use. Those detected in the study showed consistent patterns along the Brazilian coast: predominantly black, white or transparent, and less than 1 millimeter in size.

The chemical analysis identified 59.4% of them, the main components being: alkyd polymers (28.1%), used in paints and varnishes, possibly from boats and tourist vessels; cellulose (21%), which may be of natural origin (plankton, algae, marine plants and terrestrial vegetation) or of anthropogenic origin (paper, cardboard, food waste, etc.); polyethylene terephthalate (PET) (14%), commonly found in plastic packaging and synthetic fibers, released in laundry and carried to the sea by urban runoff; and polytetrafluorethylene (PTFE or teflon) (12.3%), present in non-stick and industrial coatings. The remaining 40.6% could not be described.

"Along the Brazilian coast, there are several protected areas with different levels of management. National parks, such as Abrolhos and Fernando de Noronha, are highly protected, while others, such as some APAs [environmental protection areas], allow some degree of human intervention. Our study focused on integral protection areas, called 'no-takes' in the specialized international literature, which are more restrictive marine protected areas.

"We selected ten of them: Jericoacoara National Park, Atol das Rocas, Fernando de Noronha, Rio dos Frades, Abrolhos, Tamoios, Alcatrazes, Guaraque莽aba, Carij贸s and Arvoredo," says Braga.

Global measurements

The research, conducted by doctoral student Beatriz Zachello Nunes, showed that microplastics are present in all of these APIs, with an average concentration of 0.42 卤 0.34 particles per gram of wet tissue. Among the areas studied, the highest contamination was recorded in the Alcatrazes Archipelago Wildlife Refuge, with 0.90 卤 0.59 particles per gram, while the lowest concentration was found in the Atol das Rocas Biological Reserve, with 0.23 particles per gram.

"The positive thing is that pollution in all these areas is below the international average for marine protected areas. And well below the Brazilian average for non-protected areas. Heavily contaminated areas, such as Santos and some beaches in Rio de Janeiro, are 50 to 60 times more polluted. In fact, Santos has one of the highest concentrations of microplastics in the world," says the researcher.

Bivalve mollusks (oysters, clams, mussels and others), which get their name from having a shell divided into two parts, or two articulated valves, were chosen for the study because they are considered sentinels of the sea.

"They feed by filtering seawater. The food in the water is retained in their gills, which act as sieves. And tiny cilia carry it to their stomachs. If that water contains contaminants, such as microplastics, the bivalves will retain them as well. So instead of taking water samples, which vary all the time, we analyze the bivalves because they accumulate pollutants over time and provide a more reliable history of contamination," Braga explains.

The results of the study show that plastic pollution is present even in the most restrictive environmental protection areas, with potential risks to marine ecosystems and food chains.

"The creation of MPAs alone isn't enough to stop pollution. It's essential that these areas have efficient environmental management and strict enforcement. But even this isn't enough if we consider that the microplastics may not be generated locally, but brought in from afar by the atmosphere and ocean currents. To mitigate this, only global measures, such as the Global Plastics Treaty currently being negotiated and developed under the coordination of the United Nations Environment Program [UNEP], can make a difference," concludes the researcher.