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According to National Geographic, The Great Pacific Garbage Patch is a collection of marine debris in the North Pacific Ocean. Also called the Pacific Garbage Patch, it is made up of two separate collections of debris bounded by the massive subtropical gyre of the North Pacific Ocean.

Now scientists have studied plastic waste found floating in the Great Pacific Garbage Patch and have come across a marine sponge known as Parengyodontium album.

This discovery captivated scientists because of the sponge’s unique ability to break down polyethylene, a common form of plastic pollution in the sea.

Marine sponges can reduce plastic pollution in the ocean

This fungus adds to a small list of fungi known to degrade plastic, offering a potential biological solution to combating ocean plastic pollution.

The scientists isolated the sponge from plastic waste collected from the Great Pacific Garbage Patch and studied it in the laboratory. They demonstrated the sponge’s ability to degrade plastic by subjecting it to polyethylene (PE), a common type of plastic.

The PE was treated with UV radiation to simulate exposure to sunlight, as plastic in the ocean often undergoes photodegradation. The researchers then observed the degradation of the plastic by P. album over a period of 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 assays and nanoSIMS analysis to track the incorporation of plastic-derived carbon into fungal biomass, further confirming the plastic-degrading capabilities of P. album.

These experiments provided concrete evidence of the fungi’s ability to degrade polyethylene, marking a significant step in understanding and potentially mitigating plastic pollution in the ocean.

Quantification of the degradation process

“What makes this scientific study exceptional is that we can quantify the degradation process,” lead author Annika Vaksmaa says in the paper.

The team observed that the breakdown of PE by P. album appeared to be at a rate of approximately 0.05 percent per day.

“Our measurements also showed that the fungus does not use much of the carbon coming from the PE when it breaks it down. Most of the PE that P. album uses is converted into carbon dioxide, which the fungus releases again,” added Vaksmaa.

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

Alluding to P. album, Vaksmaa explained: “In the laboratory, P. album only degrades PE that has been exposed to UV light for at least a short period of time. This means that in the ocean, fungi can only break down plastic that originally floated near the surface.

So far, only four other species are known to have plastic-degrading fungi, but a significant number of bacteria have been found to degrade plastic.

“Large amounts of plastics end up in subtropical gyres, ring-shaped currents in the oceans where the seawater is almost still,” Waksmaa said.

“This means that once the plastic has been transported there, it remains trapped there. About 80 million kilograms of floating plastic have already accumulated in the North Pacific subtropical gyre in the Pacific Ocean alone, which is only one of six major gyres in the world.

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

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

Summary of the study:

Plastic pollution in the marine kingdom is a serious environmental problem. Nevertheless, plastic can also serve as a potential source of carbon and energy for microbes, but the contribution of marine microbes, especially marine sponges, to plastic degradation is not well constrained. We isolated the fungus Parengyodontium album of floating plastic debris in the North Pacific Subtropical Gyre and measured rates of fungus-mediated mineralization (conversion to CO₂) from polyethylene (PE) by applying stable isotope probing tests with ¹³C-PE for 9 days of incubation. When PE was pretreated with UV light, the biodegradation rate of the initially added PE was 0.044 %/day. We also tracked the inclusion of PE-derived ¹³C carbon c P. album biomass using nanoSIMS and fatty acid analysis. Despite the high degree of mineralization of the UV-treated ¹³C-PE, inclusion of PE-derived ¹³C in fungal cells is insignificant and ¹³Incorporation of C was not detected for untreated PE. Together, our results reveal the potential of P. album to degrade PE in the marine environment and mineralize it to CO₂. However, the initial photodegradation of PE is crucial for P. album to metabolize PE-derived carbon.