Where is All the 'Missing' Plastic? At the Bottom of the Ocean, Study Finds

Billions of tiny plastic fragments have accumulated in the deep sea, finds a new study published this week in the journal Royal Society Open Science, raising concerns about the organisms that live there, such as coral and bottom-of-the-food-chain invertebrates.

In an attempt to find evidence of "missing" plastic debris--unaccounted for microplastic waste that should, given our "throw-away culture," be more abundant in the world's oceans--scientists looked at samples of sediment and coral retrieved from 16 sites in the Mediterranean Sea, the North Atlantic Ocean, and southwestern Indian Ocean.

What they found suggests that "[t]he deep sea floor could be the ultimate resting ground for the products of our disposable society," said Richard Thompson, a marine biologist at Plymouth University in the UK and an author of the study.

"Given the vastness of the deep sea and the prevalence of microplastics at all sites we investigated, the deep-sea floor appears to provide an answer to the question--where is all the plastic?"

Each of the dozen sediment samples contained colorful fiber fragments about the thickness of a human hair; all four coral samples carried similar fibers. The microfibers were mostly blue, black, green, or red, although vibrant colors such as pink, purple and turquoise were also seen. Rayon, which is a man-made non-plastic polymer, was detected in all the samples; polyester was also found in abundance. Potential sources for such synthetic materials are numerous, including ropes, fishing lines, clothing, packaging, and cigarette filters.

"The prevalence of plastic microfibers in all sediment cores and on all coral colonies examined suggests this contaminant is ubiquitous in the deep sea," the paper reads. "Furthermore, the wide variety of polymer types detected reveals that the accumulation and deposition of microfibers in the deep sea is complex and that they arise from a variety of domestic and industrial sources."

It continues:

Microplastic, in the form of fibers, was up to four orders of magnitude more abundant (per unit volume) in deep-sea sediments from the Atlantic Ocean, Mediterranean Sea and Indian Ocean than in contaminated sea-surface waters. Our results show evidence for a large and hitherto unknown repository of microplastics. The dominance of microfibers points to a previously underreported and unsampled plastic fraction. Given the vastness of the deep sea and the prevalence of microplastics at all sites we investigated, the deep-sea floor appears to provide an answer to the question--where is all the plastic?

Earlier this month, a separate study published in the journal PLOS ONErevealed that there are 5.3 trillion pieces of plastic, weighing nearly 270,000 tons (roughly the weight of 570 fully loaded Boeing 747s), on the surface of the world's oceans. That amount was actually lower than scientists had anticipated.

According to Newsweek: "The PLOS ONE study from last week found less plastic floating at the surface than expected. Study author Marcus Eriksen, a scientist with an environmental and research organization called 5 Gyres, hypothesizes that [this] material is more effectively 'shredded' by water currents and wave action than previously thought. It now appears that much of it is indeed ending up in the deep sea, says Eriksen, who wasn't involved in the current Royal Society paper."