Microplastics may be shifting the color of the Great Pacific Garbage Patch waters

Satellite data shows a bluer patch

Researchers at the University of Bergen in Norway report that parts of the Great Pacific Garbage Patch, the accumulation zone between California and Hawaii, have grown progressively bluer and greener over the past two decades. Their study, published on Thursday, 5 November, in the journal Communications Earth & Environment, examined satellite ocean-color records from 2002 to 2022. Within that window, the team found a clear increase in the brightness of blue and green wavelengths inside the patch and in the water near it, compared with the surrounding ocean. The change is detectable from orbit, which is how the team measured it. The researchers suggest the shift may be linked to a rising concentration of microplastics in the water.

How the team tested the cause

The researchers first examined how microplastics absorb and scatter light in seawater, comparing their optical properties with those of natural materials such as phytoplankton and minerals found in seawater. Dan Koestner, an ocean optics researcher and co-author, created laboratory mixtures from plastic debris and measured how they behaved under light sources and lasers. The laboratory data then fed simulations that tested whether a concentration of plastic could produce a color change strong enough for satellites to register. The team also modeled alternative explanations, including changes in the amount or makeup of phytoplankton. When plastics were included in the simulations, the likelihood of the characteristic blue hue seen in the satellite images rose significantly, according to the researchers.

Scale of the debris field

A 2018 study estimated about 79,000 metric tonnes of plastic in the patch, and much of that mass is abandoned fishing equipment. Microscopic fragments make up about 94% of the debris, although they account for only about 8% of its total weight. Because the debris is spread across the area rather than forming a single floating mass, it cannot be picked out in satellite pictures as one object. Estimates of the patch's size vary, with one report giving a range of 1.6 million to 4.3 million square kilometers.

What the authors have not shown

The authors stress that the link is not yet proven. Shea Cheatham, the study's lead author, told the Portuguese outlet Azul by email that the satellite signal may reflect microplastics but that the team cannot yet prove the color is caused only by them. Cheatham said the next step is fieldwork in the patch, including optical measurements of the water and a count of the microplastics present, and expressed hope that this would happen in the future. Such monitoring is difficult because particles smaller than 300 micrometers escape traditional large-scale techniques, which forces scientists to collect samples at sea and analyze them in a laboratory, a slow and costly process. Earlier experiments had already shown that these particles have optical properties capable of changing how light interacts with water, according to the study's press release.

Key dates

The satellite record analyzed by the team begins in 2002 and ends in 2022, and the paper appeared in November 2026. The 2018 tonnage estimate predates the study by eight years. The timeline below sets out these markers.

The researchers say confirming the link requires field measurements of the kind they have not yet carried out.