Shailene Woodley joined researchers gathering microplastics in the Sargasso Sea, turning a remote Atlantic ecosystem into a pollution test ground

In 2019, Shailene Woodley joined a Greenpeace trip to the Sargasso Sea, where nets found extreme microplastic pollution, including 1,298 bits in one sample.

From the deck of a ship, the Sargasso Sea looks clean. The water is a deep, calm blue, and the sea lies mostly in international waters in the North Atlantic. But in August 2019, actress Shailene Woodley joined a Greenpeace research trip there, and the nets told a different story. The team discovered “extreme” microplastic pollution there, according to a press release from Greenpeace International. One water sample alone contained 1,298 tiny bits of plastic.

What the nets pulled up

From a ship's deck, the Sargasso Sea looked clean; Shailene Woodley's trip showed otherwise. (AP Photo)

Woodley was there as a Greenpeace ambassador for the oceans. The ship, the Esperanza, was part of a wider Pole to Pole expedition to draw attention to threats to the ocean. Scientists aboard used fine nets called manta trawls that skim the sea surface to capture small pieces of plastic. The count of 1,298 was higher than what Greenpeace found in the Great Pacific Garbage Patch. The group also said its overall samples were similar to, and sometimes higher than, those collected there the previous year. Greenpeace marine biologist Celia Ojeda called the results grim news. Infrared tests done on the ship pointed to single-use plastic bottles and packaging as the likely culprit.

A nursery under pressure

One of the five ocean gyres, which are enormous circles of circulating currents, is the Sargasso Sea. These currents can carry plastic pollution from land into the sea. The sea is also named after Sargassum, a floating seaweed. The organization noted that the area is a nursery for turtles, eels and other wildlife.

Floating Sargassum gives the Sargasso Sea its name, and its mats are a nursery for sea life.

The problem didn’t begin in 2019. Oceanographer Kara Lavender Law led a 2010 Science study of plastic in the western North Atlantic and Caribbean Sea. Her team used data from 1986 to 2008. Plastic fragments, usually just millimeters in size, were found in over 60 percent of the 6,136 surface net tows. The highest concentrations were observed in the subtropical waters, where surface currents converge. Here's the shocking part. Despite rapid growth in plastic production, the study found no trends in plastic levels in the area with the most plastic. It doesn't mean the problem is going away. It just means the surface totals there didn't increase in those years.

What to keep in mind

Greenpeace is an advocacy group, and these figures are from its own expedition. This is a press release, not a peer-reviewed paper, so the results should be taken as a snapshot rather than the full story. It also says water samples collected to test for microfibers were still waiting on lab analysis. Constant described the Sargasso Sea as an important but understudied habitat, so every new batch of samples adds to the picture. The work was carried out with the 5 Gyres Institute, the University of Florida, and the Scripps Institution of Oceanography.

Greenpeace used expeditions like this one to help build the case for a global ocean treaty, and that treaty is no longer just a proposal. The UN's High Seas Treaty formally entered into force on January 17, 2026, after reaching the 60 ratifications needed to take effect, giving countries a legal path to designate places like the Sargasso Sea as fully protected ocean sanctuaries. While the sea looks clean and blue, the samples show it includes plastic that probably began as everyday items, such as bottles and packaging.