A plastic particle (red) is colonized by the marine fungus Parengyodontium album. Credit: Annika Vaksmaa/NIOZ
Key points:
- Researchers discovered that the fungus Parengyodontium album can break down the plastic polyethylene.
- P. album can only break down plastic that has first has been exposed to UV radiation, meaning it degrades plastic floating near the surface.
- Scientists hope to identify other plastic-degrading organisms in deeper parts of the ocean.
The fungus Parengyodontium album lives with other marine microbes in thin layers on plastic litter in the ocean. In a study, published in Science of the Total Environment, scientists determined that the fungus can break down particles of polyethylene (PE) – the most abundant of all plastics that have ended up in the ocean.
Researchers went to hotspots of plastic pollution in the North Pacific Ocean to locate the plastic degrading microbes. They collected plastic litter and isolated the marine fungus by growing it on specialized plastic that contained labelled carbon. Using the labelled carbon isotopes, the team could follow the carbon and trace the degradation process. They found that PE breakdown by P. album occurred at a rate of about 0.05 percent per day.
“What makes this research scientifically outstanding is that we can quantify the degradation process,” said lead author Annika Vaksmaa of the Royal Netherlands Institute for Sea Research.
In the experiments, the team discovered that the fungus requires UV-light to use PE as an energy source. This finding means that, in the ocean, the fungus only degrades plastic that has been floating near the surface.
The team expects that there are other unknown marine fungi that degrade the different plastics that sink into deeper layers of the ocean. Finding these plastic-degrading organisms is critical as humans continue to produce large amounts of plastic, and plastic waste ends up in the ocean and the seafloor.
“Large amounts of plastic end up in subtropical gyres, ring-shaped currents in the ocean in which seawater is almost stationary,” explained Vaksmaa. “Some 80 million kilograms of floating plastic have already accumulated in the North Pacific Subtropical Gyre in the Pacific Ocean alone.”