The Geeky Mind

A sea-dwelling fungus can break down the plastic polyethylene (PE) after it’s exposed to UV light from the sun, according to researchers from the Royal Netherlands Institute for Sea Research (NIOZ) and other institutions. Their findings, published in the journal Science of the Total Environment, suggest that many more plastic-degrading fungi might be living in the deeper parts of the ocean.

The fungus, Parengyodontium album, lives with other marine microbes in thin layers on ocean plastic litter. NIOZ marine microbiologists discovered that this fungus can degrade PE, the most common plastic found in the ocean. The research team collaborated with experts from Utrecht University, the Ocean Cleanup Foundation, and research institutes in Paris, Copenhagen, and St. Gallen, Switzerland. This discovery adds P. album to the very short list of known plastic-degrading marine fungi—only four species identified so far.

Tracing the Degradation Process
The researchers targeted hotspots of plastic pollution in the North Pacific Ocean. They collected plastic litter and isolated the marine fungus in the lab, growing it on special plastics containing traceable carbon isotopes (13C). “These isotopes act like a tag that helps us follow where the carbon goes during the degradation process,” explained lead author Annika Vaksmaa.

Vaksmaa is excited about the findings: “What makes this research scientifically outstanding is that we can quantify the degradation process.” In the lab, the team observed that P. album breaks down PE at a rate of about 0.05 percent per day. Most of the carbon from the PE is converted into carbon dioxide (CO2), which the fungus then releases. Although CO2 is a greenhouse gas, the amount released by the fungi is minimal, similar to what humans exhale.

The Role of UV Light
The researchers found that sunlight is crucial for the fungus to break down PE. In the lab, P. album only degraded PE that had been exposed to UV light for a short period. “In the ocean, the fungus can only degrade plastic that has been floating near the surface initially,” Vaksmaa explained. UV light alone can mechanically break down plastic, but it also enables marine fungi to biologically degrade plastic.

Hunting for More Plastic-Degrading Fungi
Since much plastic sinks to deeper ocean layers before being exposed to sunlight, P. album can’t break it all down. However, Vaksmaa believes other, yet undiscovered, fungi in deeper ocean parts may also degrade plastic. “Marine fungi can break down complex carbon materials. With numerous marine fungi out there, it’s likely that more species contribute to plastic degradation. There are still many questions about how this process works in deeper ocean layers,” said Vaksmaa.

The Urgent Need to Address Plastic Pollution
Finding plastic-degrading organisms is critical. Humans produce over 400 billion kilograms of plastic annually, a figure expected to triple by 2060. Much of this plastic ends up in the ocean, from the poles to the tropics, floating in surface waters, sinking to greater depths, and eventually settling on the seafloor.

Lead author Annika Vaksmaa highlighted the urgency: “Large amounts of plastics end up in subtropical gyres, ring-shaped ocean currents where seawater is almost stationary. Once plastic gets trapped there, it accumulates. In the North Pacific Subtropical Gyre alone, around 80 million kilograms of floating plastic have already accumulated, and this is just one of the six large gyres worldwide.”

This discovery of a plastic-degrading fungus offers a glimmer of hope in the fight against ocean plastic pollution, suggesting that with more research, we might find more natural solutions to this pressing environmental issue.