Scientists detect ocean color change near garbage patch — ScienceAlert
Scientists at the University of Bergen in Norway have detected a change in the color of water near the Great Pacific Garbage Patch. An analysis of satellite observations from 2002 to 2022 showed a statistically significant increase in ocean brightness in the blue and green wavelength ranges, creating a gradual bluish-green tint. As ScienceAlert reports, this signal may correspond to the optical properties of microplastics.
Satellite signal
The Great Pacific Garbage Patch is located in a system of circular ocean currents in the North Pacific, where plastic debris accumulates. It is not a solid mass of waste, but a dispersed concentration of plastic that currents transport and concentrate.
Researchers Shea Cheatham, Daniel Kestner, and Berge Hamre first studied in the laboratory how microplastic fragments absorb and scatter light in seawater. Modeling showed that at concentrations potentially present in the garbage patch area, plastic can create an optical effect detectable by satellite observations.
Microplastics usually absorb almost no light in the visible spectrum, but scatter it intensely. Therefore, water may become brighter in both the blue and green ranges. Phytoplankton and dissolved organic matter alter the color of water differently, while measurements at a nearby research station indicated a stable pattern of mineral dust deposition throughout the observation period.
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On-site measurements are needed
The authors of the study emphasize that satellite data do not conclusively prove that microplastics were the cause of the color change. According to their calculations, in relatively rare cases, certain combinations of natural changes in seawater composition can produce a similar signal. To verify the conclusion, measurements of the optical properties of water samples directly in the garbage patch area and an assessment of microplastic concentration are needed.
According to a 2018 study, the garbage patch contained approximately 1.8 trillion plastic fragments with a total mass of about 79,000 metric tons. A significant share of the mass consists of abandoned fishing gear. At the same time, microplastics account for an estimated 94% of fragments by number, although they make up only about 8% of the mass of the debris.
Scientists noted that large plastic waste can be removed during cleanup, whereas removing microplastics from the water column, especially the smallest particles, is practically impossible. The study was published in the journal Communications Earth & Environment.
