Plastic debris swept through the seas by wind and waves has piled up in large areas of the North Pacific Ocean, collectively dubbed the “Great Pacific Garbage Patch.”
But on this raft of trash in the open sea, researchers found something they did not expect: a surprisingly high number of marine plants and animals thought to live only on coasts. These out-of-place species survived alongside ocean-dwellers on the debris, the team reported last week in the journal Nature Ecology & Evolution—and some even reproduced on the trash.
“To find that many coastal species on a relatively small sample size was shocking,” Linsey Haram, a marine ecologist who conducted the research while at the Smithsonian Environmental Research Center, tells NPR’s Nell Greenfieldboyce.
The Great Pacific Garbage Patch occupies water between North America’s west coast and Japan. A system of swirling ocean currents called a gyre pulls trash into a couple of different patches across the Pacific.
Contrary to the image that the term “garbage patch” may conjure, the site is not just a pile of massive chunks of trash—much of the debris is tiny pieces of plastic that the human eye cannot easily see. But the pollution spans about 610,000 square miles, and the plastic debris contained there weighs an estimated 79,000 metric tons.
Researchers had previously found evidence that coastal species could survive in the open ocean after a 2011 earthquake struck off the coast of Japan. This event led to a tsunami that swept coastal debris away from the shore and toward the United States. Between 2012 and 2017, plastic debris holding 381 Japanese coastal species washed up on North American and Hawaiian beaches as a result of the tsunami, according to the paper.
For the new research, the scientists examined 105 pieces of debris retrieved from the open ocean garbage patch between California and Hawaii, including bottles, buoys, nets, ropes and crates. They found coastal species from 37 different invertebrate taxa on 70.5 percent of the items.
These species included shrimp-like arthropods, sea anemones and mollusks, as well as species native to the coast of Japan, such as Pacific oysters, orange-striped anemones and ragworms, per the Wall Street Journal’s Nidhi Subbaraman.
“I was surprised that they saw such high numbers of coastal species,” Sabine Rech, a marine biologist at the Catholic University of the North in Chile, tells NPR.
Coastal organisms and open-ocean organisms lived together on two-thirds of the debris pieces. But this wasn’t necessarily a peaceful coexistence: For one, the team found coastal sea anemones eating open-water-dwelling sea snails. And the two types of organisms may have competed for space or food.
Researchers used to think that coastal species couldn’t thrive at sea. But some coastal life not only survived, but managed to reproduce on the trash. Crustaceans were taking care of eggs and anemones were cloning themselves.
But coastal species’ adaptability to the open ocean might not be a good sign for ecosystems as a whole.
“If you can reproduce, then you can spread. And if you can spread, you can invade,” Linda Amaral-Zettler, a marine microbiologist at the Royal Netherlands Institute for Sea Research who did not contribute to the work, tells Scientific American’s Meghan Bartels.
Essentially, the researchers found a habitat in the open ocean that was enabled by human pollution. This complicates the idea of cleaning up the garbage patch, reports the Wall Street Journal.
“These are species that have rafted out with coastal debris and have now successfully found essentially a novel habitat out there,” James Carlton, a co-author of the study and a marine scientist at Williams College, tells New Scientist’s Madeleine Cuff.
“As humans, we are creating new types of ecosystems that have potentially never been seen before,” Ceridwen Fraser, a biogeographer at the University of Otago in New Zealand who was not involved in the study, tells the Atlantic’s Sarah Zhang.
In future work, the team wants to find out if coastal organisms in other parts of the world have made similar journeys out to sea with the assistance of plastic waste. If so, researchers have a lot to learn about how these communities might interact with the ecosystems around them or travel to new areas.
“I would fully expect that as a result of this we will see more invasions of coastal zones,” Carlton tells New Scientist.