How Microplastic Is Poisoning the Ocean Ecosystem

Seabirds found filled with fishing lines, sea turtles choking on discarded shopping bags, and a plastic soup spreading out bigger than Texas in the Pacific are among the most poignant images of plastic pollution in the oceans. However, damage is also done on a level that’s nearly invisible to the naked eye. Marine worms normally consume silt, important for “eco-engineering” the shorelines, but as plastic washes ashore and into the sediment the worms are also ingesting smaller-than-a-millimeter bits of plastic, which research has found causes their energy levels and silt-consumption to drop. Given the importance of worms to the ocean ecosystem, this has implications for everything that relies on the ocean, including humans.

Some 20 million tons of plastic pollution goes into the ocean each year, and it’s not biodegrading. Through exposure to the elements, plastic can break into smaller and smaller pieces, which, along with small plastic beads from hygiene products and microfibers from synthetic fabric, become a form of pollution known as a "microplastic."

In a study published in Current Biology, researchers from the Universities of Exeter and Plymouth in the UK found that lugworms living on beaches contaminated with microplastics had less energy and ate less sediment. Another study drawing from the research found that ingesting microplastic can also introduce harmful chemicals into the lugworms, including hydrocarbons, antimicrobials, and flame-retardants. Once inside the lugworms, the plastic is a part of the food chain, as lugworms are an important and edible part of the shoreline environment.

It’s been known that plastic vanishes from the global waste stream every year, but where it goes from there has been largely ignored.

“We are losing a large volume of plastic and we know it is going into the environment and the assumption being made by policymakers is that this material is non-hazardous, it has got the same ranking as scraps of food,” study co-author Mark Browne told the BBC.

"Our laboratory studies provide the first clear evidence that microplastics could cause harm and show that this could result from both the physical presence of ingested plastic and chemical transfer,” said Richard Thompson, professor of marine biology at Plymouth University, on Phys.org. “Our next steps will be to establish the full implications of these findings for organisms in natural habitats."

Those implications could be fairly far-reaching. In addition to being a food source, marine worms do for the shoreline what earthworms do for a garden, by eating organic matter and preventing the build-up of silt on the shore. "If the animals are not able to eat as much then there is a change in the function of the organisms and there is an impact on the semblance of the species found in an area," Browne said. He went on to explain how the potentially significant changes to marine worms can be for an ecosystem. "If you look at the total biomass of a shoreline, about 32 percent can be made up from these organisms,” he said.

To Browne, the study reveals that it’s probably time for policy makers to reexamine and reassess how plastics and plastic debris are classified, and address how it ends up in the environment. It might be hard to hold a “Save the Lugworm” rally, but when it comes to microplastics, it’s the things that are easiest to swallow that you have to watch out for.