Decadal evolution of microplastic concentration in the GPGP. Mean (circles) and standard error (whiskers) of microplastic mass concentrations measured by surface net tows conducted in different decades, within (light blue) and around (dark grey) the GPGP. Dashed lines are exponential fits to the averages expressed in g km−2: f(x) = exp(a*x) + b, with x expressed in number of years after 1900, a = 0.06121, b = 151.3, R2 = 0.92 for within GPGP and a = 0.04903, b = −7.138, R2 = 0.78 for around the GPGP. Graphic: Lebreton, et al., 2018 / Scientific Reports

Delft, the Netherlands, 22 March 2018 (The Ocean Cleanup) – 1.8 trillion pieces of plastic weighing 80,000 metric tons are currently afloat in an area known as the Great Pacific Garbage Patch - and it is rapidly getting worse. These are the main conclusions of a three year mapping effort conducted by an international team of scientists affiliated with The Ocean Cleanup Foundation, six universities and an aerial sensor company. Their findings were published today in the journal Scientific Reports.

The Great Pacific Garbage Patch (GPGP), located halfway between Hawaii and California, is the largest accumulation zone for ocean plastics on Earth. Conventionally, researchers have used single, fine-meshed nets, typically less than a meter in size, in an attempt to quantify the problem. However, this method yields high uncertainty because of the small surface area that is covered. Additionally, these methods could not measure the magnitude of the problem to its fullest extent, because all sampling nets - small and large - were unable to capture objects greater than the size of the net.

In order to analyze the full extent of the GPGP, the team conducted the most comprehensive sampling effort of the GPGP to date by crossing the debris field with 30 vessels simultaneously, supplemented by two aircraft surveys. Although most vessels were equipped with standard surface sampling nets, the fleet's mothership RV Ocean Starr also trawled two six-meter-wide devices, which allowed the team to sample medium to large-sized objects.

To increase the surface area surveyed, and quantify the largest pieces of plastic - objects that include discarded fishing nets several meters in size - a C-130 Hercules aircraft was fitted with advanced sensors to collect multispectral imagery and 3D scans of the ocean garbage. The fleet collected a total of 1.2 million plastic samples, while the aerial sensors scanned more than 300 km2 of ocean surface.

The results, published today in Scientific Reports, reveal that the GPGP, defined as the area with more than 10 kg of plastic per km2, measures 1.6 million square kilometers, three times the size of continental France. Accumulated in this area are 1.8 trillion pieces of plastic, weighing 80.000 metric tons, the equivalent of 500 Jumbo Jets. These figures are four to sixteen times higher than previous estimates. 92% of the mass is represented by larger objects; while only 8% of the mass is contained in microplastics, defined as pieces smaller than 5 mm in size.

“We were surprised by the amount of large plastic objects we encountered", said Dr. Julia Reisser, Chief Scientist of the expeditions. "We used to think most of the debris consists of small fragments, but this new analysis shines a new light on the scope of the debris.”

By comparing the amount of microplastics with historical measurements of the GPGP, the team found that plastic pollution levels within the GPGP have been growing exponentially since measurements began in the 1970s. Laurent Lebreton, lead author of the study, explains: “Although it is not possible to draw any firm conclusions on the persistency of plastic pollution in the GPGP yet, this plastic accumulation rate inside the GPGP, which was greater than in the surrounding waters, indicates that the inflow of plastic into the patch continues to exceed the outflow.”

Boyan Slat, Founder of The Ocean Cleanup and co-author of the study, elaborated on the relevance of the findings for his organisation’s cleanup plans: “To be able to solve a problem, we believe it is essential to first understand it. These results provide us with key data to develop and test our cleanup technology, but it also underlines the urgency of dealing with the plastic pollution problem. Since the results indicate that the amount of hazardous microplastics is set to increase more than tenfold if left to fragment, the time to start is now.”

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Alan Dunton
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Grayling, San Francisco
David Schraeder
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T: +1 646 552 1322

Great pacific garbage patch growing rapidly, study shows


Modelled and measured mass concentration in the Great Pacific Garbage Patch (GPGP). (a) Ocean plastic mass concentrations for August 2015, as predicted by our data-calibrated model. The bold black line represents our established limit for the GPGP. (b) Microplastics (0.05–0.5 cm) mass concentrations as measured by Manta trawl (n = 501 net tows, 3.8 km2 surveyed). (c) Mesoplastics (0.5–5 cm) mass concentrations as measured by Manta trawl; d) Macroplastics (5–50 cm) mass concentrations as measured by Mega trawl (n = 151 net tows, 13.6 km2 surveyed); (e) Megaplastics (>50 cm) mass concentrations as estimated from aerial imagery (n = 31 mosaic segments, 311.0 km2 surveyed). All observational maps are showing mid-point mass concentration estimates as well as the predicted GPGP boundaries for the corresponding sampling period: August 2015 for net tow samples, and October 2016 for aerial mosaics. Graphic: Lebreton, et al., 2018 / Scientific Reports

ABSTRACT: Ocean plastic can persist in sea surface waters, eventually accumulating in remote areas of the world’s oceans. Here we characterise and quantify a major ocean plastic accumulation zone formed in subtropical waters between California and Hawaii: The Great Pacific Garbage Patch (GPGP). Our model, calibrated with data from multi-vessel and aircraft surveys, predicted at least 79 (45–129) thousand tonnes of ocean plastic are floating inside an area of 1.6 million km2; a figure four to sixteen times higher than previously reported. We explain this difference through the use of more robust methods to quantify larger debris. Over three-quarters of the GPGP mass was carried by debris larger than 5 cm and at least 46% was comprised of fishing nets. Microplastics accounted for 8% of the total mass but 94% of the estimated 1.8 (1.1–3.6) trillion pieces floating in the area. Plastic collected during our study has specific characteristics such as small surface-to-volume ratio, indicating that only certain types of debris have the capacity to persist and accumulate at the surface of the GPGP. Finally, our results suggest that ocean plastic pollution within the GPGP is increasing exponentially and at a faster rate than in surrounding waters.

Evidence that the Great Pacific Garbage Patch is rapidly accumulating plastic

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