plastic just They were submerged in the ocean near Falmouth, England, for a week, but during that time had developed a thin layer of biofilm, a sticky mix of mucus and microbes, on their surfaces. Microbiologist Michiel Vos of the University of Exeter, UK, sank five different types of plastic as tests. He and his colleagues wanted to know which of the myriad microbes living in the ocean would attach to these introduced materials.
Vos and his colleagues are primarily concerned with pathogenic bacteria. To understand the extent to which plastic can be colonized by potentially deadly bacteria, the scientists injected biofilms into wax moth larvae. After a week, four percent of the larvae had died. But four weeks later, after Vos and his team let the plastic soak in the ocean for a while, they repeated the test. This time, 65 percent of the wax moths died.
Scientists analyze biofilms: Plastic is covered in bacteria, including some known to make us sick. They found pathogens that cause urinary tract, skin and stomach infections, pneumonia and other diseases. To make matters worse, these bacteria also carry a broad spectrum of antimicrobial resistance genes. “The plastic you find in water is quickly colonized by bacteria, including pathogens,” Vos said. “It doesn’t matter what plastic it is.”
It’s not just bacteria that hitch a ride on plastic.Biofilms on ocean plastics can also hide parasite, Virusand toxic algae. With ocean plastic pollution so pervasive — found everywhere from the bottom of the Mariana Trench to Arctic beaches — scientists worry that plastic is transporting these human pathogens around the ocean.
But whether plastics host dense enough populations of pathogens to be actually dangerous, and whether they will carry them into new territories, are tough questions to answer.
There is good reason to believe that plastics are accumulating and spreading pathogens around the world. Linda Amaral-Zettler, a microbiologist at the Royal Netherlands Institute for Sea Research, coined the term plastic ball For the new ecosystems created by plastics, plastics are different from other hard surfaces that people often find in the ocean — like logs, shells and rocks — because plastics are durable, long-lived, and many float. “It makes it fluid,” she said.
Plastic can travel long distances.For example, after the 2011 Japan earthquake and tsunami, many identifiable Japanese objects washed up on the west coast of North AmericaThe trash “has the potential to transport anything that is attached to it,” Amaral Zettler said.
Recent laboratory work has also shown that some typical terrestrial disease-causing parasites can survive in seawater and infect marine mammals. These protozoan parasites—specifically, Toxoplasma gondii, Cryptosporidiumand Giardia intestinalis— Can attach to microplastics in seawater. This could change where, when and how these parasites accumulate in the ocean.
“If they hitch a ride on plastic that happens to be in the same sewer outlet, onshore runoff from a river or storm drain, then they end up where the plastic ends up,” Shapiro explained. This could be in shellfish on the seafloor , or floating in the currents in the middle of the ocean.
The next step, Shapiro explained, is to look for a similar link between parasites and plastic outside the lab.
For Vos, microplastic contamination appears to be a breeding ground for pathogens, raising a long-standing concern that plastic could contribute to the spread of antibiotic resistance. Bacteria can exchange genes, and because the bacteria are in close contact on tiny microplastic surfaces, there is a high level of horizontal gene transfer between them, he said. Plastics also allow bacteria to come into close contact with pesticides and other contaminants that also stick to biofilms. This encourages the development of antimicrobial resistance.
“We know very little about this,” Voss said, “but there are some interesting ways that bacteria can experience stronger selection. [for antimicrobial resistance] On plastic, but there are also more opportunities to swap genes that might confer resistance. “
In addition to the potential risks to human health, plastic-borne pathogens could threaten marine ecosystems and food supply chains, Amaral-Zettler said. Millions of people rely on seafood as a source of protein, and there are many pathogens that can infect the fish and shellfish we eat. Microplastics have the potential to spread disease between different aquaculture and fishing areas, Amaral-Zettler said.
While we don’t fully understand the risks, these studies are another good argument for limiting plastic pollution, Vos said. “There can’t be anything positive about plastic with pathogens floating around.”