99 Percent of Microplastic in the Ocean is Missing—Scientists Just Worked Out How to Find It

Fluorescent dye could be the answer to finding the 99 percent of missing microplastics in the oceans.

Researchers from the University of Warwick in the United Kingdom have discovered that a dye can bind with plastic particles—which makes the microplastics easy to see underneath a fluorescence microscope. Microplastics—as small as the width of a human hair—are difficult to track down, and previous research has suggested only 1 percent of plastic waste in the oceans has been found. Using fluorescent dye could help to distinguish natural materials from tiny plastic particles, says the report published in Environmental Science & Technology earlier this month.

“Have we found the lost 99 percent of missing plastic in surface oceans?” Joseph A. Christie-Oleza, co-author and research fellow studying marine molecular microbiology at the University of Warwick, said in a statement. “Obviously this method needs to be implemented in future scientific surveys to confirm our preliminary findings.”

RTX4KS0 Plastic bags from a mountainous rubbish dump on the Sidon seafront in south Lebanon floats in the Mediterranean November 12, 2007. Reuters

Our oceans have been understood to be terribly polluted with plastics, but the extent is difficult to measure when plastics break down to miniscule levels. Plastics have been found as deep as seven miles below the sea surface. A disheartening photo of a seahorse grasping a cotton swab made its rounds on the Internet—as a wildlife photographer captured photos while snorkeling amongst garbage and raw sewage. Even corals are eating plastics because they taste like food to them, the New York Times reported.

This new method to find microplastics, if further validated in future research, can help measure the pervasiveness of microplastics in the oceans. “It is important to understand how plastic waste behaves in the environment to correctly assess future policies,” said Christie-Oleza.

This method, which researchers say is inexpensive, was tested on samples of sea surface water and beach sand from the English coast around Plymouth. After using their method on the samples, researchers detected a larger amount of even smaller microplastics than previous estimates and significantly more than would have been found with traditional methods.

RTX13PYZ Plastic bottles and general waste are piled up at a beach in Panama City, Panama September 4, 2013. Reuters

The microplastic that was most abundant in their samples was one called polypropylene, which is found in plastics used for packaging and food containers. The method was also effective in finding plastics that make up items such as plastic bags and Styrofoam. 

Current methods mostly require manually picking microplastics out of samples, according to the researchers. The fluorescent dye could replace that method, ideally curbing some of the human subjectivity associated with visually sorting the microplastics from natural materials.

“Using this method, a huge series of samples can be viewed and analyzed very quickly, to obtain large amounts of data on the quantities of small microplastics in seawater or, effectively, in any environmental sample,” Gabriel Erni-Cassola, lead author and PhD candidate at the University of Warwick, said in a statement.