Fungi break down ocean plastic

Fungus Parengyodontium album It lives along with other marine microbes in thin layers of plastic debris in the ocean. Marine microbiologists at the Royal Netherlands Institute for Sea Research (NIOZ) have discovered that fungi are capable of breaking down polyethylene (PE) particles, the largest of all plastics that end up in the ocean. NIOZ researchers collaborated with colleagues from Utrecht University, the Ocean Cleanup Foundation and research institutes in Paris, Copenhagen and St. Gallen, Switzerland. The discovery allows the fungus to join a very short list of plastic-degrading marine fungi: only four species have been identified to date. It is already known that large numbers of bacteria are capable of degrading plastic.

Follow the decomposition process precisely

Researchers went to find plastic-degrading microbes in hotspots of plastic pollution in the North Pacific Ocean. From the collected plastic debris, they isolated marine fungi by growing them in the laboratory on special plastics called carbon. Waxma: „These are called ¹³C isotopes are found continuously in the food chain. It’s like a tag that helps us follow where the carbon goes. We can find it in decay products.”

Waksma is excited about the new discovery: „What makes this research scientifically outstanding is that we can measure the degradation process.” In the lab, Waksma and his team observed the breakdown of PE B album Occurs at a rate of 0.05 percent per day. „Our measurements show that the fungus does not use much of the carbon from PE when breaking down. Most PE B album The application is converted into carbon dioxide, which the fungus excretes again. Although CO₂ As a greenhouse gas, this process is not something that poses a new problem: the amount released by fungi is a fraction of what humans release when they breathe.

Only under the influence of UV

The researchers found that sunlight is essential for the fungus to use PE as an energy source. Waksma: “In the lab, B album Only PE exposed to UV-light for at least a short period of time breaks down. That means, in the ocean, the fungus can initially only degrade plastic that floats close to the surface,” Waksma explains. „It was already known that UV-light mechanically breaks down plastic, but our results show that it facilitates biological plastic breakdown by marine fungi.”

There are other fungi

As various plastics sink into deeper layers before being exposed to sunlight, B. Album Not all of them can be broken. Waksma anticipates that there are other, as-yet-unknown fungi that degrade plastic in the deep parts of the ocean. „Marine fungi can break down complex materials made of carbon. There are many marine fungi, so besides the four species identified so far, other species may also contribute to plastic degradation. There are still many questions about the dynamics of how plastic degradation takes place in deeper layers,” says Waksma.

Plastic soup

Identifying plastic-degrading organisms is urgent. Every year, humans produce 400 billion kilograms of plastic, and this is expected to at least triple by 2060. Most of the plastic waste ends up in the ocean: from the poles to the tropics, it floats on the surface. The water reaches great depths in the ocean and eventually falls to the bottom of the ocean.

Annika Waksma, lead author of NIOZ: “Large amounts of plastics end up in subtropical gyres, ring-shaped currents in oceans where seawater is nearly constant. This means that once the plastic is taken away, it gets stuck there. About 80 million kilograms of floating plastic has already accumulated in the North Pacific subtropical gyre in the Pacific Ocean, one of the six largest gyres worldwide.