Home · Science · Nov 6 archive
Microplastics May Be Brightening Pacific Ocean Near Garbage Patch
· Confirmed
In Short: A new study suggests microplastics could be altering the color of the Pacific Ocean near the Great Pacific Garbage Patch.
Researchers from the University of Bergen in Norway have found that the accumulation of microplastics, defined as plastics under 300 μm in diameter, may be causing the ocean to brighten in blue and green wavelengths near the Great Pacific Garbage Patch.
Satellite observations from 2002 to 2022 revealed a subtle but statistically significant brightening of the ocean in these wavelengths, indicating a gradual cyan tint.
The study, published in the journal Communications Earth & Environment, utilized a Monte Carlo approach to generate over 50,000 ocean brightening spectra, determining the likelihood that the observed brightening is attributable to microplastics.
Shea Cheatham, one of the study's authors, explained, “The ocean’s color is created from the interaction of sunlight with seawater and all the things contained in it, and therefore the color is indicative of the ocean’s content.”
The researchers identified distinct shifts in ocean color caused by microplastic inclusion in radiative transfer simulations of oligotrophic waters, with low densities of microplastics (~2 mg m −3 ) causing an aberrant brightness exceeding the satellite-based Ocean and Land Color Instrument (OLCI) signal-to-noise ratio with a peak at 490 nm.
Standard methodologies for the characterization of small microplastics are laborious with limited upscaling potential; however, recent measurements in the North Atlantic suggest abundances of suspended microplastics ranging 32–651 μm in diameter may already be as high as 10 4 particles per cubic meter in the upper 200 m of the water column.
According to the nonprofit The Ocean Cleanup, the Great Pacific Garbage Patch covers about 1.6 million square kilometers (roughly 620,000 square miles), about twice the size of Texas.
The concentration of microplastics in the garbage patch may have become high enough to change the color of the ocean in which they drift, with tiny fragments of microplastic accounting for an estimated 94 percent of the pieces floating in the patch, although only 8 percent of its total mass.
The researchers emphasize that their findings do not yet prove that microplastics have directly brightened the ocean, though their results are backed up by lab experiments with microplastics.
Background
A new study published in the journal Communications Earth & Environment suggests that microplastics may be altering the color of the Pacific Ocean, particularly near the Great Pacific Garbage Patch.
New research suggests microplastics in the Great Pacific Garbage Patch are causing the ocean to take on a cyan tint.
What's confirmed
- However, decades of satellite ocean color measurements have revealed long-term changes in the ocean’s optical signature, which may be influenced by the aggregation of small suspended microplastics in some regions.
- The accumulation of small microplastics (defined as plastics under 300 μm in diameter) poses a unique and alarming challenge, as these suspended plastic particles are difficult to directly measure in situ, nearly impossible to remove from the water column, impact marine ecosystems and carbon cycling, likely compose the majority of plastics entering the food web, and are continuously generated through photodegradation and mechanical breakdown of larger plastic debris 1, 2, 3, 4, 5, 6.
- 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.
- 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.
- To better understand how microplastics may have influenced the ocean’s color, Koestner and his colleagues looked at 20 years of satellite data from the spot in the ocean with perhaps the most of plastic—the Great Pacific Garbage Patch, a zone between Hawaii and California where trash trapped by ocean currents accumulates.
- The results, published in the journal Communications Earth & Environment on Thursday, don’t yet prove that microplastics have directly brightened the ocean, the researchers emphasize, though their findings are backed up by lab experiments with microplastics.
- Near the surface of the ocean in parts of the garbage patch, microplastic densities may reach up to 17 milligrams per cubic litre.
- The sea around the Great Pacific Garbage Patch is changing colour, and microplastics may be to blame.
- The Great Pacific Garbage Patch (GPGP), located roughly midway between Hawaii and California, covers around 1.6 million square kilometres and is thought to contain nearly 80,000 tonnes of plastic debris, carried there by ocean currents.
What's still developing
- The researchers themselves stress that their finding is not yet proof. „We’re still one step away from proving definitively“ that plastics are the cause, Ms. Cheatham told Scientific American. „We just have to get in there to verify.“ That means traveling to the garbage patch to take optical measurements of water samples, a tricky and expensive undertaking.
- The study adds to the growing body of evidence linking microplastics to changes in ocean color, highlighting the need for further research to confirm the direct impact of microplastics on the ocean's optical properties.
- Something strange is happening to the Pacific Ocean.
- Microplastics accounted for approximately 94% of those pieces, although larger debris made up most of the mass.
- In other words, the observed blue-green brightening was much easier to reproduce when the models allowed microplastic concentrations to change.
- Vast amounts of discarded plastic accumulate in the oceans, sometimes forming enormous garbage patches that threaten marine life.
- Instead of disappearing, these materials gradually fragment into increasingly smaller particles, including microplastics and nanoplastics.
- The most likely culprit, they say, is microplastics.