Plastic Preys on Deep-Sea Organisms

Until now, it was not known whether deep-sea organisms were as deeply affected by human plastic wastes as their shallow-dwelling counterparts. Image courtesy of Pixabay (CC0 Public Domain).

The dangers of oceanic plastic pollution are well known: throughout social media, trending videos portray turtles trapped in plastic netting and decomposed birds with plastic in their stomachs. The reality of plastic pollution is heart-wrenching, and researchers are continuously producing more evidence to demonstrate the extent of the problem.

Discoveries from the past twenty years have revealed that organisms living in shallow waters and the middle layers of the ocean ingest copious amounts of plastic. Most recently, however, researchers at the University of Oxford discovered that deep-sea organisms—rarely studied in this context until now—are also consuming plastic at alarming rates. Their finding is particularly concerning because it demonstrates the vast impact of human plastic pollution: our trash has reached one of the Earth’s most remote and fragile environments.=

Conducted primarily by Michelle Taylor and Lucy Woodall at Oxford, the research concentrates on microfibers, the most common type of microplastic found in the environment. Microplastics are small plastic pieces, usually less than five millimeters in diameter (the width of a thumbtack), that are created when larger plastic debris is weathered and broken apart, while microfibers are a sub-class of fiber-shaped microplastics that often come from fibers on clothing. They are particularly dangerous for aquatic wildlife because they can easily get trapped in an animal’s digestive track or gills, lessening its feeding ability, damaging its digestive track, and often leading to its starvation. Organisms also face contamination by concentrated organic pollutants and metals that are harbored by the plastics.

Taylor and Woodall’s research was inspired by earlier findings that discovered microplastics in deep-ocean sediments. “We were discussing what deep-sea animals eat, which is mostly particle matter falling from shallower waters—something called marine snow, and if this snow would have microplastics in it,” said Taylor, a senior postdoc at Oxford.

The researchers explored deep-sea organisms in the equatorial mid-Atlantic and southwest Indian Ocean by sending a robot to the seafloor to scoop up organism samples. Reaching such depths was a major challenge, but the research team had access to a UK research ship and the Remote Operated Vehicle Isis robot, which can reach depths of 6000 meters. From their collected samples, they studied three distinct phyla: Cnidaria (such as jellyfish and corals), Echinodermata (such as starfish and sea cucumbers), and Arthropoda (such as crustaceans). The researchers recorded the depth where each organism was found, the type of microplastic it had interacted with, and the microplastic’s location on or within the organism. Most of the studied organisms, such as squat lobsters, corals, and sea cucumbers, contained microplastics in their oral areas, stomachs, and gills, indicating that the plastics were either ingested or inhaled. For example, the researchers found microplastics made of polypropylene, a polymer that can carry compounds such as DDE, a pesticide.

The logical follow-up question is what we can do about human plastic pollution, but the answer is difficult because of the sheer prevalence of plastics in daily life. “It’s surprising how much clothing we wear is made up entirely of acrylic or polyester—I challenge you to check yours now,” said Taylor.

Scientists are currently designing safer plastics. Paul Anastas, the Director of Yale’s Center for Green Chemistry and Green Engineering, says research should focus on developing biodegradable plastics that do not persist in the environment. “There is a worldwide network of people producing these solutions and they need to be implemented much more rapidly.” The twelve principles of green chemistry include designing safer chemicals, using safer solvents, and reducing energy use.

Governments, too, are taking measures to reduce the amount of plastic waste released into marine environments. In December of 2015, President Obama signed the Microbead-Free Waters Act, banning the cosmetics industry from using plastic microbeads, such as the exfoliating beads in facial soaps that are washed down the drain and released into the ocean.

The public also has a responsibility to keep plastics out of our oceans. We can trash the “throw-away” mentality that leads us to use disposable plastic cups and utensils, and opt for reusable options like cloth bags at the grocery store. And in the meantime, Taylor hopes to see further research that probes deep-sea plastic pollution.