Environment: Microplastic blues — Great Pacific Garbage Patch seawater is changing colour (Communications Earth & Environment)

Parts of the Pacific Ocean within the Great Pacific Garbage Patch appeared to change colour between 2002 and 2022, with some areas becoming significantly bluer and greener. New research, published in Communications Earth & Environment, suggests that an increased concentration of microplastics in the seawater may be responsible.

Ocean pollution from microplastic particles less than 300 micrometres across is difficult to measure directly because current methods are labour-intensive and cannot be applied at scale. However, laboratory experiments suggest that microplastics of this size have optical properties that may allow their concentration in seawater to be measured remotely. The Great Pacific Garbage Patch is suitable for testing this as in situ measurements in 2016 showed that the seawater near the surface may contain over 17 milligrams of larger microplastic particles per cubic metre.

Shea Cheatham and colleagues analysed three satellite ocean colour datasets of the northeast Pacific Ocean between 2002 and 2022. They found significant brightening for blue and green wavelengths in and around the Great Pacific Garbage Patch. This likely resulted in the water appearing more cyan (a blue-green mix) compared to the surrounding ocean. The authors then modelled how microplastic concentration affected ocean brightening across the visible light spectrum, and whether these changes could be due to common natural causes of ocean colour change. They found that even small microplastic concentrations increased brightness across the visible spectrum, with the greatest increase occurring at cyan wavelengths. Cyan brightening occurred four times more often in simulations involving microplastics (13%) than in simulations with only natural factors (3%). They also found that this cyan brightening would be detectable by satellite sensors at microplastic concentrations of approximately 5 milligrams per cubic metre of seawater.

The authors say that their results suggest that seawater becoming more cyan could indicate an increase in microplastic concentration. However, they caution that different satellite datasets showed different colour change estimates, and that natural environmental factors may differ in other ocean regions. They say that direct measurements of microplastic concentrations and properties near the Great Pacific Garbage Patch are needed to confirm the findings and improve future monitoring efforts.

Article

• Open access
• Published: 05 November 2026

Cheatham, S., Koestner, D. & Hamre, B. The ocean’s color is changing near the Great Pacific Garbage Patch. Commun Earth Environ 7, 855 (2026). https://doi.org/10.1038/s43247-026-04071-0

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