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Anela Choy, a former MBARI postdoctoral fellow, led this study on microplastics. In this photo, she is preparing a microplastic sampling device mounted on the MBARI remotely operated vehicle. Ventana. Image: Susan von Thun © 2017 MBARI
Many people have heard of the Great Pacific Garbage Patch, a vast ocean space between California and Hawaii, where ocean currents concentrate plastic pollution. However, there may also be a lot of plastics far from the surface of the ocean.
A study recently published in Scientific reports shows that plastic debris less than 5 millimeters in diameter, called microplastics, is common from the surface to the bottom of the sea. It is also possible that it enters marine food webs, both on the surface and in depth. Finally, the study suggests that most of this microplastic comes from consumer products.
This is the first study to systematically examine microplastics, with repeated sampling at the same locations and over a range of depths from just below the surface of the ocean to depths of 1,000 meters.
The study at the Monterey Bay National Marine Sanctuary in California also revealed that small marine animals were consuming microplastics, which introduce particles into food webs from near-surface waters to the ocean floor.
"Our findings confirm a growing body of scientific evidence that deep sea water and animals, the Earth's largest habitat, are the largest deposit of small plastic debris," said Anela Choy, lead author of the paper. .
"Our study demonstrates a link between microplastics distributed in the water column and the entry of this foreign material into marine food webs by important marine animals, such as pelagic crabs and larvae. of giants. "
MBARI engineers spent a great deal of time and effort developing a device to collect and filter microplastics at the bottom of the surface of Monterey Bay. Image: © 2017 MBARI
The groundbreaking research was a joint effort of the Monterey Bay Aquarium Research Institute (MBARI) and the Monterey Bay Aquarium. Choy led the research as a postdoctoral fellow at MBARI. She is currently Assistant Professor at the Scripps Institution of Oceanography at the University of California San Diego.
Kakani Katija, a MBARI engineer from the team, added, "This research shows how we can leverage scientific, technical and conservation expertise to develop new technologies that provide powerful information. on the impact of human activities on the ocean.
Microplastic is ubiquitous of the surface at the bottom of the sea
Using MBARI submarine robots, equipped with sampling devices specifically designed for this project, researchers have filtered plastic particles from seawater repeatedly in two locations and at different depths. five to 1000 meters below the surface of Monterey Bay, California. Some samples were collected just off Moss Landing Harbor, but most of them were collected about 25 kilometers from shore in the deep waters of Monterey Canyon.
The results surprised the team. They found almost identical concentrations of microplastic particles near the surface and in the deepest waters studied. More surprising perhaps, they found about four times more concentrations of microplastic particles in the medium water zone (200 to 600 meters deep) than in near-surface waters.
Microplastic was found in all sampled animals
In addition to sampling water, researchers also examined concentrations of microplastic particles in specimens of two marine species filtering into the water column: pelagic red crab and giant larvae. The team found microplastic in all the animal specimens studied.
The researchers found microplastic particles in deep-sea larvae (left) and pelagic red crabs (right). Left image © MBARI; Right Image © Monterey Bay Aquarium
Pelagic red crabs and giant larvae resembling tadpoles are essential parts of the ocean food chain. Pelagic red crabs are usually found in large numbers near the ocean surface, where they are consumed by many species of fish, including tuna. Larvae create large mucus filters that collect organic matter – and microplastics – and throw away these filters, which are eaten by other animals as they sink to the bottom of the ocean.
More microplastics in samples from consumer products than fishing gear
Equipped with a microscope and a laboratory technique called Raman spectroscopy, researchers from Arizona State University contributed to the study.
The most abundant plastics found – polyethylene terephthalate (PET), polyamide and polycarbonate – are commonly used in consumer products, including food and beverage packaging, such as single-use bottles and take-away containers. Most microplastic particles discovered by researchers were highly altered, suggesting that they have been in the environment for months or even years.
Although commercial fishing is practiced in Monterey Bay, researchers found very little polypropylene or other plastic particles commonly used in local fishing gear. The researchers also detected more microplastic particles off the coast.
The plastic found in the depths of Monterey Bay was of the same type as that commonly found in consumer goods. Image: Hank Armstrong / Monterey Bay Aquarium
"This suggests that most of the particles do not come from local fishing gear," explained Kyle Van Houtan, chief scientist at the Monterey Bay Aquarium and one of the co-authors of l & # 39; study. "This also suggests that at least some of the microplastic has been transported into the region by ocean currents."
This discovery could indicate that plastic is widespread in the depths of the ocean and may even concentrate there.
Bruce Robison, senior researcher at MBARI and co-author of the paper, said, "These results are intriguing and point to the need for similar deep-water surveys elsewhere to determine the extent of the problem."
Van Houtan then explained the importance of the study and proposed a solution. "The ubiquitous presence of plastic pollution in the water column indicates that reducing the source – starting with producing and using less plastic – is one of the most effective ways to solve this problem," he said. he declares.
"It may be virtually impossible to remove existing microplastics from the sea bed," he continued. "But when we slow down the flow of plastic from the earth, we can help prevent the growing plastic buildup in our global ocean."
(Joint Press Release with Monterey Bay Aquarium and Scripps Oceanographic Institute)
Original newspaper article:
Choy, CA, Robison, BH, Gagne, TO, Erwin, B., E. Firl, E., Halden, UK, Hamilton, JA, K. Katija, SE, C. Rolsky, C. Van Houtan, KS (2019 ). Vertical distribution and biological transport of marine microplastics in the epipelagic and mesopelagic water column, Scientific reports, 9, 7843, doi: https://doi.org/10.1038/s41598-019-44117-2 (June 6, 2019)
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