Microplastics are now invading fully protected marine areas

Marine protected areas in Brazil are often viewed as safe havens for biodiversity. But even the strictest of these zones aren’t free from pollution.

A new study shows that microplastics are turning up in these supposedly untouched waters, raising concerns about the true extent of environmental protection.

The research was carried out by scientists from the Federal University of São Paulo (UNIFESP) in collaboration with Australian colleagues.

The team examined ten marine protected areas (MPAs) categorized under the highest level of restriction, known as “integral protection areas.” These places prohibit all forms of human activity, including tourism.

Remote waters are affected

To measure the level of pollution, researchers used bivalve mollusks such as oysters and mussels. These creatures filter seawater to feed and naturally collect any contaminants in their tissues. That makes them ideal for monitoring long-term pollution trends in the ocean.

Ítalo Braga is the coordinator of the research funded by FAPESP and professor at the Institute of Marine Science of the Federal University of São Paulo (IMar-UNIFESP) in Brazil.

“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,” said Braga.

These findings are alarming because they confirm that pollution can infiltrate even areas that are theoretically shielded from human interference. Plastic particles don’t respect borders. They travel freely on air and ocean currents, spreading their impact across vast distances.

Microplastics invading protected areas

The microplastics discovered in these marine areas were mostly smaller than 1 millimeter and appeared in shades of black, white, or transparent. Chemical analysis identified 59.4% of the particles.

The most common materials included alkyd polymers (28.1%), typically used in paints and varnishes and likely originating from boats or marine equipment.

Cellulose made up 21% and was traced to both natural sources, such as algae and marine plants, and human-made materials like paper waste.

Polyethylene terephthalate (PET), which is commonly found in synthetic fabrics and plastic packaging, accounted for 14% of the identified microplastics. Another 12.3% consisted of polytetrafluoroethylene (PTFE or Teflon), often used in non-stick and industrial coatings.

The remaining 40.6% of the particles could not be identified, underscoring the complex and varied nature of marine plastic pollution.

Microplastics found in every protected area

The team studied ten sites across Brazil: Jericoacoara National Park, Atol das Rocas, Fernando de Noronha, Rio dos Frades, Abrolhos, Tamoios, Alcatrazes, Guaraqueçaba, Carijós, and Arvoredo. All showed signs of contamination.

“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,” said Braga.

“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.”

Alcatrazes Archipelago Wildlife Refuge had the highest contamination, with 0.90 ± 0.59 particles per gram of wet tissue. Atol das Rocas Biological Reserve had the lowest, with 0.23 particles per gram. Across all sites, the average was 0.42 ± 0.34 particles per gram.

Better than average – but still concerning

In some ways, the results were encouraging. The contamination levels were below the international average for marine protected areas. They were also far lower than the levels found in unprotected Brazilian coastal zones.

“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,” noted doctoral student Beatriz Zachello Nunes.

“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.”

Even so, the findings suggest that pollution is now a truly global problem. Local restrictions are not enough if foreign sources continue to push contaminants into protected zones.

Why bivalves matter

The use of bivalves was key to this study. These animals serve as nature’s filters. Because they remain in place and continually filter the same waters, they offer a clearer picture of what’s happening over time.

“Bivalve mollusks (oysters, clams, mussels and others) 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,” explained Braga.

“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.”

This approach avoids the fluctuations that come with direct water sampling and offers a more accurate view of long-term pollution.

Protected areas need support

The results serve as a warning. Marine protected areas are no longer safe from microplastics. More effort is needed to enforce rules, manage these areas effectively, and – crucially – reduce pollution at the source.

“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,” said Braga.

“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.”

Efforts at the international level may be the only way to protect even the most isolated marine ecosystems from invisible but dangerous plastic pollution.

The full study was published in the journal Environmental Research.

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