In the summer of 2020, Friends of Palm Beach, a nonprofit that cleans the shores of Palm Beach, Fla., noticed something unusual among the typical debris—many bottles and rubber bales were washing up covered in a black residue. Diane Buhler, the group’s founder, cataloged the time and location of the arrival of each piece of debris and kept an expertly photographed record.
No oil spills had been reported locally, and the high amount of residue-coated debris created a mystery: Where was all this black sludge coming from?
Christopher Reddy, a chemical oceanographer at the Woods Hole Oceanographic Institution, had been working with an international team of scientists on a separate mystery: the origins of a 2019 oil spill in Brazil, the largest in the country’s history. When he saw the debris posted on the Friends of Palm Beach Instagram page, he reached out. “I was like, ‘Please, please send [the debris] to us,’” he said. The details Buhler was providing about the debris, he said, were “remarkably informative.”
View this post on Instagram
Reddy and the team had a hunch: They thought the 2020 Florida debris and the 2019 Brazil spill were linked. Because of weathering, oil residues rarely travel more than 300 kilometers (186 miles)—but perhaps they’d used plastic pollution to hitch a ride to the Sunshine State.
“This project wouldn’t have happened unless there was this knowledge of the way the currents move.”
A thorough analysis, published in Environmental Science and Technology, confirmed the residue likely originated from the Brazil spill. The findings reinforce scientists’ hypothesis that oil can travel far greater distances when attached to plastic debris in the ocean.
Matching Mysterious Oil Samples
Multiple lines of evidence informed the team’s conclusion that the Brazil spill and Palm Beach debris were related. First, previous experiments that tracked drifting bottles in the western tropical Atlantic and Caribbean Sea in the 1960s and 1970s showed it was possible for plastic debris to drift thousands of kilometers in the time that elapsed between the spill and the appearance of the debris. Second, computer simulations of the movement of oiled debris in the ocean also showed that it was possible for such debris to have reached Florida’s shores from the coast of Brazil.
“This project wouldn’t have happened unless there was this knowledge of the way the currents move,” said Reddy, a coauthor on the new study.
In the summer of 2020, oiled debris was found on Florida beaches. The oil likely traveled 8,500 kilometers (about 5,300 miles) from a 2019 oil spill off the coast of Brazil. Credit: James et al., 2026,
https://doi.org/10.1021/acs.est.5c14571,
CC-BY 4.0
The researchers also scraped oil residue from 10 samples of the Palm Beach debris, then performed a series of chromatography tests and molecular analyses to compare it to oil samples from the Brazilian spill. Researchers found the samples to be forensically identical to oil from the spill; compounds that the team expected to be present were, while ones that should have been lost as oil degraded were not.
“It was such crystal-clear evidence that I got nervous.”
The team was astounded at the similarities, particularly the chromatography results. “It was such crystal-clear evidence that I got nervous,” Reddy said. “Oh my gosh, this really did happen,” he remembered thinking.
The data are “pretty striking,” agreed Bryan James, a chemical engineer at Northeastern University and coauthor on the new study.
The research team reasoned that the oiled debris traveled about 8,500 kilometers (about 5,300 miles) from the coast of Brazil to Palm Beach over about 240 days. That much oil has never been documented traveling so far, said Michel Boufadel, an environmental engineer at the New Jersey Institute of Technology who was not involved in the study.
Researchers think the oiled debris may also have reached Caribbean islands but wasn’t cataloged. Credit: Diane Buhler, Friends of Palm Beach
The authors think it’s likely that similar debris washed up on Caribbean shores as well as Florida’s but simply wasn’t collected or cataloged. “Southeast Florida was where there was a person thinking and looking, who had this database in her head” and reported it, too, Reddy said.
While the “science is solid,” Boufadel said, additional evidence from elsewhere in the Caribbean would add confidence to the results.
A Plastic Problem
Typically, oil spilled in the ocean is removed by natural processes before it reaches very far, James said. But plastic debris can travel much farther, sometimes washing ashore after traveling thousands of miles over decades.
James said this raises a colocation problem. Many sources of oil and sources of plastic overlap, creating a “greater possibility for these two to find each other…and continue to move oil farther from where it originated,” he said.
The results are further proof of a known risk of plastic pollution: It can be a vector for other toxic substances, Boufadel said.
The research team is investigating why plastic debris can carry oil residues so far. Boufadel said it’s likely the plastic helped to maintain the physical integrity of the oil, preventing some of the fragmentation and degradation that would otherwise have occurred.
Colleagues in Brazil, Reddy added, are continuing to investigate the origin of the still-mysterious 2019 spill there, as well. It may be oil that leaked from the SS Rio Grande, a German supply boat sunk by the U.S. Navy in 1944, but more research is needed to confirm that hypothesis, Reddy said.
—Grace van Deelen (@gvd.bsky.social), Staff Writer
This news article is included in our ENGAGE resource for educators seeking science news for their classroom lessons. Browse all ENGAGE articles, and share with your fellow educators how you integrated the article into an activity in the comments section below.
Citation: van Deelen, G. (2026), Plastic debris helps oil residues reach farther across the ocean,
Eos, 107, https://doi.org/10.1029/2026EO260033. Published on 20 January 2026.
Text © 2026. AGU.
CC BY-NC-ND 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
