Researchers from the University of Bergen say microplastics in the Great Pacific Garbage Patch, a vast accumulation of plastic in the North Pacific Ocean, may be responsible for a subtle shift in ocean color, a cyan tint detected in satellite observations from 2002 to 2022. The study, published in Communications Earth & Environment, suggests the optical effect may occur at microplastic concentrations potentially already present in the patch, but says further sampling is needed to establish whether microplastics are responsible.
The Great Pacific Garbage Patch is a vast, diffuse accumulation of plastic in the North Pacific gyre. A 2018 survey estimated it contained around 1.8 trillion pieces of plastic, weighing 79,000 metric tons. Much of that mass consists of discarded fishing equipment, and a later study traced a substantial proportion of larger debris to fishing industries in Japan, China, South Korea, Taiwan and the United States. Microplastics account for an estimated 94% of the pieces.
Ocean optics specialists Shea Cheatham, Daniel Koestner and Børge Hamre began by studying how microplastics interact with light in the laboratory, comparing their optical properties with naturally occurring materials such as phytoplankton and minerals. The researchers observed properties suggesting microplastics may scatter and absorb light differently enough to produce distinctive optical signatures. Their simulations suggested the effect may occur at concentrations potentially already present in the garbage patch, and the researchers examined whether current satellites could detect the signatures.
When the researchers examined satellite records from 2002 to 2022, they found a subtle but statistically significant brightening in blue and green wavelengths near the patch, a gradually growing cyan tint consistent with their simulations. "We were shocked, excited, and a little alarmed to see the same shift in ocean color on the map after we analyzed the first satellite dataset of the garbage patch," Cheatham told ScienceAlert. "Our first reaction was disbelief, which is what led us to check two other satellite datasets just to convince ourselves that it was even remotely possible that we could be seeing the same signature evident in our models."
The brightening at both blue and green wavelengths is unusual. Phytoplankton and dissolved organic matter absorb different wavelengths, so they are unlikely to produce quite the same signature. Mineral dust can also brighten the ocean, but measurements from a nearby research station showed a stable pattern of dust deposition over the study period. The researchers found that certain combinations of natural environmental changes could produce a similar effect, although these scenarios were relatively rare in their simulations.
To fully answer whether microplastics are the cause, Cheatham said the team needs to go to the garbage patch to make optical measurements of water samples and quantify the microplastics present. She expressed hope that this work can be done in the future.
Microplastics may also present the biggest challenge to cleaning up the patch, despite accounting for only a small proportion of its mass. “Removing microplastics from the water column, particularly the smallest plastics we focus on in our study, is essentially impossible,” Cheatham said. “At present, the only way to reduce microplastic pollution is to prevent them from entering the water in the first place.”
Analysis
Why This Matters
- The discovery suggests that plastic pollution may have reached such high concentrations that it is changing the appearance of the ocean on a large scale, potentially affecting marine ecosystems and the food web.
- Microplastics are the most difficult to remove from the water and can enter the base of the marine food chain, eventually reaching humans.
- The finding intensifies calls to prevent further plastic waste from entering the ocean, as cleanup of tiny fragments is effectively impossible.
Background
The Great Pacific Garbage Patch is a massive accumulation of plastic debris in the North Pacific Ocean, held together by ocean currents. A 2018 survey estimated it contains 1.8 trillion pieces of plastic, weighing around 79,000 metric tons. Most of the larger debris comes from fishing industries in Japan, China, South Korea, Taiwan and the United States, but microplastics, tiny fragments less than 5mm in size, make up 94% of the pieces. These microplastics can absorb toxic chemicals and are easily ingested by marine life.
What to Watch
- The researchers plan to conduct direct sampling of water in the garbage patch to confirm whether microplastics are causing the colour shift. An expedition could provide definitive evidence.
- Continued satellite monitoring may show whether the cyan tint is spreading or intensifying over time.
- The study could increase pressure on governments and industries to reduce plastic production and improve waste management.
Checked
12 claims in this story checked against 1 source: 12 supported.
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- SupportedThe Great Pacific Garbage Patch may be turning the ocean cyan, according to the study.ScienceAlert: “Across satellite observations spanning 2002 to 2022, the researchers identified a subtle but statistically significant brightening of the ocean in blue and green wavelengths near the Great Pacific Garbage Patch – a gradually growing cyan tint. It was consistent with the optical signature that their simulations had predicted microplastics might produce.”
- SupportedSatellite data spanning two decades showed blue- and green-wavelength brightening consistent with microplastics.ScienceAlert: “Across satellite observations spanning 2002 to 2022, the researchers identified a subtle but statistically significant brightening of the ocean in blue and green wavelengths near the Great Pacific Garbage Patch – a gradually growing cyan tint. It was consistent with the optical signature that their simulations had predicted microplastics might produce.”
- SupportedUniversity of Bergen researchers say microplastics may be responsible for a subtle ocean-colour shift near the patch.ScienceAlert: “The concentration of microplastics in the garbage patch may have become high enough to change the color of the ocean in which they drift, according to a new study by ocean optics specialists Shea Cheatham, Daniel Koestner, and Børge Hamre of the University of Bergen in Norway.”
- SupportedThe study was published in Communications Earth & Environment.ScienceAlert: “The research has been published in Communications Earth & Environment .”
- SupportedCheatham said further sampling is needed to establish whether microplastics caused the colour shift.ScienceAlert: ““To fully answer the question of whether microplastics themselves are the root cause of this ocean color shift, we will need to go to the garbage patch to make optical measurements of water samples and quantify the microplastics present,” Cheatham said.”
- SupportedCheatham told ScienceAlert, “We were shocked, excited, and a little alarmed to see the same shift in ocean color on the map after we analyzed the first satellite dataset of the garbage patch,”ScienceAlert: “"We were shocked, excited, and a little alarmed to see the same shift in ocean color on the map after we analyzed the first satellite dataset of the garbage patch," Cheatham told ScienceAlert.”
- SupportedCheatham told ScienceAlert, “Our first reaction was disbelief, which is what led us to check two other satellite datasets just to convince ourselves that it was even remotely possible that we could be seeing the same signature evident in our models.”ScienceAlert: “"Our first reaction was disbelief, which is what led us to check two other satellite datasets just to convince ourselves that it was even remotely possible that we could be seeing the same signature evident in our models."”
- SupportedA 2018 survey estimated the patch contained around 1.8 trillion pieces of plastic weighing 79,000 metric tons.ScienceAlert: “A 2018 survey estimated that it contained some 1.8 trillion pieces of plastic, weighing around 79,000 metric tons.”
- SupportedMicroplastics account for an estimated 94% of the pieces in the patch.ScienceAlert: “accounting for an estimated 94 percent of the pieces floating in the patch”
- SupportedMeasurements from a nearby research station showed a stable pattern of dust deposition over the study period.ScienceAlert: “measurements from a nearby research station showed a stable pattern of dust deposition over the study period.”
- SupportedCheatham said removing microplastics from the water column, particularly the smallest plastics studied, is essentially impossible.ScienceAlert: “"Removing microplastics from the water column, particularly the smallest plastics we focus on in our study, is essentially impossible, and these plastics are the most likely to enter the base of the marine food web and end up on your plate," Cheatham said.”
- SupportedCheatham said preventing microplastics from entering the water is currently the only way to reduce microplastic pollution.ScienceAlert: “"At present, the only way to reduce microplastic pollution is to prevent them from entering the water in the first place."”
