Scientists have shown that some wild corals are shredding on plastic trash. The new study published in Proceedings of the Royal Society B: Biological Sciences
focused on a temperate species of coral collected off Rhode Island, one of those small building blocks no larger than a human fist. But researchers say the findings are more than that of a tropical family, so they are more likely to be consumed by microplastics.
The new results to the growing sense that microplastics are ubiquitous in the environment, from tall mountain peaks to the deepest ocean trenches. Many organisms, from fish to birds, have been found to eat small bits of plastic. So do humans, through tainted water and food sources.
When Boston University coral biologist Randi Rotjan, who started his career in marine ecosystems, did not expect to focus on plastics.
"Plastics keep interrupting the conversation, and it's hard to ignore," Rotjan said.
Worse than junk food
Rotjan and her colleagues collected four colonies of wild Astrangia poculata You 196 196rang 196ystem jystem jystem jystem microystem microystem microystem. a small coral that lives off the US Atlantic coast from Massachusetts to the Gulf of Mexico. They look at their study site, off the coast of Rhode Island, because it's close to an urban environment – Providence is 24 miles away-that could be expected to pollute the water.
Back in the laboratory, the researchers cut open the individual coral polyps and counted the number of microplastics. They found more than 100 small fibers in every polyp. Although this was the first record of microplastics in wild coral, earlier research had already shown that same coral species consumed plastic in a laboratory setting.
They presented lab-raised coral polyps with fluorescent blue microbeads-bits of plastic that were recently used in soaps, cosmetics, and medications-at the same time as a natural food, brim shrimp eggs, which are thus about the size of a pinhead
Every single polyp that gave the choice almost twice as many microbeads as brine shrimp eggs.
"I was totally shocked by the results," said co-author Jessica Carilli, a scientist at the Naval Information Warfare Center Pacific in San Diego, CA. "They are not necessarily interested in any particles that float within reach of their tentacles … .They unfortunately preferred plastic to actual food."
Government banned the use of microbeads in 2015, but the ban only went into effect a little over a year ago.
Vectors of disease
In an additional feeding experiment, the researchers put the microbeads in a seawater to cover them with a biofilm-a thin layer of bacteria. In the ocean, co-author Koty Sharp, a coral microbiologist at Roger Williams University in Rhode Island, explained that most microplastics are likely to be coated with bacteria. The researchers read the biofilm on their microbeads with the common intestinal bacteria E. coli dyed fluorescent green to make them easy to track.
More than 48 hours after swallowing the microbeads, the polyps spit them back out. But even after that, the glowing E. coli persisted inside the coral's digestive cavity. All coral polyps that ate the E. coli -laced microbeads within two weeks.
"This is the most interesting part of the study. No one has looked at this vector of disease pathogens before, "said Joleah Lamb, an ecologist at University of California, Irvine who was uninvolved with the study. Lamb has surveyed hundreds of coral reefs, documenting disease and pollution by large plastic trash items. [Research]published in Science last year, found that disease in coral increased by 20-fold after plastic made contact with the coral.
Although E. coli is not common in the ocean, many other microbes, and they are focused on the surface of microplastics.
Other corals may not respond to microbeads or the bacteria they carry in the same way; Rotjan's team has studied just one species so far.
"I'm terrified of the mess we've created in our oceans," Rotjan said. "But this is just part of the story for us to motivate cleaning it."