A plastic chewing sea sponge found in the Great Pacific Garbage Patch

According to national geography, the Great Pacific Garbage Patch is a collection of marine debris in the North Pacific Ocean. Also called the Pacific Debris Gyre, it consists of two distinct collections of debris bounded by the massive North Pacific Subtropical Gyre.

Now, scientists have examined plastic debris found in the floating Great Pacific Garbage Patch and have come across a marine sponge known as Album Parengyodontium.

The discovery captivated scientists thanks to the sponge’s unique ability to break down polyethylene, a common form of marine plastic pollution.

Sea sponge could give way to ocean plastic pollution

This fungus joins a small list of fungi known to degrade plastic and offers a potential biological solution to combating plastic pollution in the oceans.

Scientists separated the fungus from plastic debris collected from the Great Pacific Garbage Patch and examined it in the laboratory. They demonstrated the sponge’s ability to degrade plastics by subjecting it to polyethylene (PE), a common type of plastic.

The PE was treated with UV light to simulate exposure to sunlight, as plastic often undergoes photodegradation in the ocean. After that, the researchers monitored the breakdown of the plastic by P. album for some time.

They quantified the rate of plastic degradation and analyzed the conversion of polyethylene to carbon dioxide.

In addition, they used advanced methods such as stable isotope probing assays and nanoSIMS analysis to monitor the incorporation of plastic-derived carbon into the fungal biomass, further confirming the plastic-degrading capabilities of P. album.

These experiments provided concrete evidence of the sponge’s ability to degrade polyethylene, a significant step toward understanding and possibly mitigating ocean plastic pollution.

Quantification of the degradation process

“What makes this research scientifically exceptional is that we can quantify the degradation process,” lead author Annika Vaksmaa said in the paper.

The team noticed that the decay of PE by P. album appears to be at a rate of roughly 0.05 percent per day.

“Our measurements also showed that the fungus does not use much of the carbon coming from the PE during decomposition. Most of the PE used by P. album is converted into carbon dioxide, which the fungus then excretes,” added Vaksmaa.

The discovery of the sea sponge represents a major step forward in the race to mitigate climate change and reduce plastic pollution accumulating in the marine environment.

Referring to P. album, Vaksmaa explained: “In the laboratory, P. album degrades only PE that has been exposed to UV radiation for at least a short time. This means that in the ocean, the sponge can only degrade plastics that initially float near the surface.”

Until now, only four other species were known to have plastic-degrading fungi, however, a significant number of plastic-degrading bacteria were found.

“A large amount of plastic ends up in subtropical gyres, ring currents in the oceans in which the seawater is almost stationary,” Vaksmaa said.

“That means once the plastic gets transferred there, it’s stuck there.” Around 80 million kilograms of floating plastic has already accumulated in the North Pacific subtropical gyre in the Pacific Ocean, which is only one of six large gyres in the world.”

The research was carried out by marine microbiologists from the Royal Netherlands Institute for Marine Research (NIOZ) in collaboration with scientists from Utrecht University, Ocean Cleanup Copenhagen and the Swiss St. Gallen.

The study was published in the journal – Science of the Total Environment.

Study abstract:

Plastic pollution in the marine area is a serious environmental problem. However, plastic can also serve as a potential source of carbon and energy for microbes, but the contribution of marine microbes, especially marine sponges, to the degradation of plastics is not sufficiently limited. We isolated the fungus Album Parengyodontium from floating plastic debris in the subtropical North Pacific Gyre and measured rates of sponge-mediated mineralization (conversion to CO₂) of polyethylene (PE) by applying stable isotope probing tests with ¹³C-PE for 9 days of incubation. When the PE was pretreated with UV light, the biodegradation rate of the originally added PE was 0.044%/day. We further monitored the incorporation of PE-derivative ¹³C carbon do P. album biomass using nanoSIMS and fatty acid analysis. Despite the high degree of mineralization of the UV treated ¹³C-PE, incorporation of PE derived ¹³C to fungal cells was smaller and ¹³C incorporation was not detectable for untreated PE. Together, our results reveal the potential P. album to the degradation of PE in the marine environment and its mineralization to CO₂. However, the initial photodegradation of PE is essential for P. album metabolize the carbon derived from PE.