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Tiny marine organisms sitting at the very bottom of our food chain are ingesting the plastics that humans are tossing by the ton into the world's oceans, say researchers in a new study published in the Archives of Environmental Contamination and Toxicology.
The British Columbia-based scientists studied two species of zooplankton — a microscopic organism found in the oceans, seas, and freshwater — and discovered they were mistaking plastic for food, raising serious concerns about potential risks to all other species located above them in the food chain.
"Zooplanktons are the grazers at the bottom of the food chain and they are absolutely critical food for virtually everyone in the food web," Peter Ross, one of the study authors and director of the Vancouver Aquarium's Ocean Pollution Research Program, told VICE News. "They are consumed by all ages and stages and size of fish, notably when they are young."
Ross and his colleagues studied copepods and euphausiids — two crustacean species that feed on phytoplankton for sustenance — and found that one out of every 34 copepods and one out of every 17 euphausiids were ingesting plastic particles. The zooplankton were collected from the waters near British Columbia during an oceanographic cruise, and kept in glass jars full of seawater, where their feeding patterns were monitored and recorded by the researchers.
When an organism — especially one as small as a zooplankton — swallows plastic, a few things can happen. The creature might be able to pass the particle through its digestive tract, or the plastic might remain in its body, leaching toxic chemicals. If the plastic doesn't leak chemicals, it can make the creature feel full, inhibiting it from eating.
Whether slowly leaching into the zooplankton's tissue or remaining in its digestive tract, the plastic is eventually passed on to bigger creatures that feed on the zooplankton. The authors estimated that baby salmon inhabiting coastal British Columbia can end up ingesting two to seven microplastic particles everyday — and adults as many as 90 pieces of plastic.
"The public, the scientific community, and government agencies have long recognized that garbage, nets, debris — basically macroplastics — have represented a visible and gruesome threat to the top of the food chain," Ross said. "And now we may have the same problem at the bottom of the chain."
Jenna Jambeck, a professor of environmental engineering at the University of Georgia, conducted a study on the amount of plastic in the ocean, using data from 192 coastal countries. She found that about 275 million metric tons of plastic waste was generated in these countries in 2010, with 4.8 to 12.7 million metric tons entering the oceans. The study was the first of its kind estimate of plastic pollution in the world's oceans. Jambeck predicts that without improvements in waste management methods, the total amount of plastic waste entering the oceans might increase ten times by 2025.
Two types of plastic are wreaking havoc in the ocean: large, visible items and smaller particles almost invisible to the naked eye. These smaller particles, known as microplastic, pose the highest threat to marine organisms. Microplastic can be formed by the sea, sun, and wind breaking down larger items of plastic. But it is also an ingredient in cosmetics like facial scrubs and toothpaste. These particles, called microbeads, represent a big chunk of the plastic waste floating around the oceans, which has prompting several US states to ban their production.
Ross said the two major sources of the plastic eaten by the zooplankton were the smaller particles that resulted from the breakdown of bigger items such as plastic bottles, and plastic fibers shed by synthetic textiles and ropes while getting washed. The researchers did not find any microbeads ingested by zooplankton.
"We don't know where these fibers are coming from. But we do suspect that sewage is releasing several of these particles. We found a lot of polyester and nylon," Ross said. Synthetic textiles, like polyester and nylon, are essentially woven out of plastic fibers. These materials can shed thousands of fibers in a single wash, which then end up in the ocean by way of wastewater systems.
And, because the average American consumed nearly 15 pounds of seafood in 2013, humans might also be ingesting plastics.
Cameron Ainsworth, a professor at University of South Florida's College of Marine Science, said the immediate concern was less about direct impacts on humans, though, and more on the indirect ones. "The danger is mainly to the marine ecosystem, which human beings rely on not only for food, but employment and recreation as well," he said.
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