The Great Pacific Garbage Patch may now have so much plastic, it’s changing the color of the ocean

By Laura Paddison, CNN

(CNN) — Far out in the Pacific Ocean, between Hawaii and California, a wide patch of water has been changing color over the past two decades, becoming significantly bluer and greener. It may sound inviting, but scientists have discovered there may be a disturbing reason for it: increasing plastic pollution.

This part of the ocean is called the Great Pacific Garage Patch. It’s a swirling soup of plastic trash made up of everything from old fishing nets to food and drink packaging. People often think of it as vast islands of visible waste, but in reality, much is made up of tiny fragments called microplastics, many too small to be seen by the naked eye.

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And it’s an increase of these tiny plastic pieces that may be responsible for changing the color of the Great Pacific Garage Patch’s water, according to a study published Thursday in the journal Communications Earth & Environment by scientists from the University of Bergen in Norway.

The color of the ocean is a literal reflection of what’s in it — from microscopic plant-like organisms called phytoplankton to marine debris. But there was a “gap” in research around how microplastics could affect the ocean’s color, said Dan Koestner, a study author and ocean optics research scientist.

He started making “smoothies” out of plastic waste and testing the material using lights and lasers to see how microplastics interacted with light.

With that data, the next step was to see how much plastic would be needed for there to be a color change detectable by a satellite, Koestner said. The Great Pacific Garbage Patch, where giant rotating ocean currents trap huge amounts plastic debris, seemed ideal.

The researchers analyzed 20 years of satellite data from the area, between 2002 and 2022, and found significant brightening for blue and green wavelengths in and around the Great Pacific Garbage Patch compared to the surrounding ocean. This likely made the water a cyan color, they concluded.

The researchers then ran simulations to understand the potential causes of the color change, and tested whether it could be due to natural reasons, like more or different phytoplankton. But it was when they added plastics that they found a big increase in the likelihood the water would change to the cyan color seen on satellite.

“We were able to say that we have this specific spectrum of light, this color that microplastics tend to produce,” said Shea Cheatham, a report author and PhD candidate at the University of Bergen.

There is still work to be done to prove the color seen in the satellite data “is directly and exclusively caused by plastics,” Cheatham said. The next step is to go to the Garbage Patch and take direct measurements — a tricky and expensive process.

If their conclusions are proved correct, this analysis could be applied to other parts of the ocean believed to have high concentrations of microplastics, to help understand more about the scale of the problem. “We don’t really have a good way of quantifying or measuring these really small microplastic particles without laborious methods,” Koestner said.

Scientists have estimated up to around 13 million metric tons of plastics enter the ocean each year, but only a fraction of has been found floating at the surface — around 250,000 tons.

The disparity is sometimes called the “missing plastic paradox” and part of the issue could be the fragmentation of plastics into tiny, hard-to-detect microplastics. “We’re definitely lacking closure in terms of where the plastic goes,” Cheatham said.

Microplastics can cause widespread harm. They can be eaten by marine animals and travel up through the food chain, and have even been found in the seafood we eat. They can also carry pollutants and even interfere with the ocean’s ability to move and store carbon.

The ability to detect plastics using satellites and drones has increased considerably over the last decade, but microplastics are challenging because they are tiny and also tend to be mixed with things like phytoplankton and natural debris, said Richard Thompson, a marine biology professor at the University of Plymouth in England, who was not involved in the research. “Detecting a plastic related signal is very challenging,” he said.

That’s why these findings are important, he added. “If we can detect change remotely from satellites it will be faster and less costly than counting debris piece by piece.”

Koestner hopes the study might help bring home the extent of the pollution problem. If “microplastics are accumulating at a level that’s actually altering the ocean’s color, that’s pretty alarming.”

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