Juanita Urban-Rich finds high concentration of plastics in corals living in Narragansett Bay
UMass Boston Professor Juanita Urban-Rich is part of a team of researchers that is the first to show that some corals are eating tiny bits of plastic debris found in the ocean. The team discovered that these corals often prefer “microplastics” over natural food, even as the plastic potentially carries harmful bacteria that can kill them.
“What we found was both surprising and sad,” said Urban-Rich, an associate professor of zooplankton ecology.
A type of coral called Astrangia poculata ingested the microplastics both in the wild and in the lab, and Urban-Rich and her coauthors write in a new paper published in Proceedings of the Royal Society B that the lab-raised corals liked the tiny bits of plastic better than “normal food,” such as brine shrimp eggs.
They know this because they dumped shrimp eggs and plastic microbeads into tanks of lab-raised corals. When they later cut the corals open, they found that there was twice as much plastic inside as shrimp eggs, as shown below.
“Corals are an important animal as they eat small microscopic animals the size of a lot of microplastics,” Urban-Rich said. “The temperate coral Astrangia poculata actually derives a lot of its energy for survival from particles it eats opposed to tropical reef corals that also get much of their energy from photosynthesis from their symbiotic dinoflagellate.”
Urban-Rich started this study in 2016 alongside former colleague Jessica Carilli, Randi Rotjan of Boston University, and a student in the NSF-funded CREST-REU Program at UMass Boston, Eliya Baron Lopez. Urban-Rich’s biggest contribution was examining wild corals collected from Narragansett Bay, selected because of its proximity to the urban area of Providence.
“We found high concentrations of plastic in the corals and a lot of plastic fibers, much higher than I expected,” Urban-Rich said.
Urban-Rich and her collaborators brought in Koty Sharp of Roger Williams University and found that bacteria, at times harmful bacteria, would grow on the microplastics as a biofilm. They then laced the biofilm with E. coli and fed the beads to lab-raised corals. Even though the corals spit out the beads two days later, they all died from E. coli infections. These findings suggest corals in the wild might be dying because of infections carried by plastics.
“It’s sad. I’m also concerned as much of the plastic in the wild corals were fibers that have a high surface area and thus a potentially great ability to transport more bacteria and other pollutants into the corals,” Urban-Rich said.
Urban-Rich is also part of other studies looking at the amount of plastic in corals from tropical reefs.