Scientists suggest that the problem of microplastic pollution in the oceans could be exacerbated by plankton consuming these particles.
Researchers have found that a specific type of zooplankton, which exists in both saltwater and freshwater, is capable of consuming and breaking down microplastics. However, this discovery may not be beneficial in addressing the issue of plastic pollution in aquatic environments. In fact, the tiny organisms, called rotifers, could be exacerbating the problem by breaking down the plastic particles into even smaller and potentially more hazardous nanoplastics.
Each rotifer, named from the Latin for “wheel-bearer” owing to the whirling wheel of cilia around their mouths, can create between 348,000 and 366,000 nanoplastics – particles smaller than one micrometre – each day.
The tiny creatures, found in large quantities, are present everywhere and can be found in numbers of up to 23,000 per liter of water in a single area. A group of scientists led by the University of Massachusetts Amherst discovered that in Poyang Lake, the biggest lake in China, rotifers produce a staggering 13.3 quadrillion plastic particles per day.
Plastic can take up to 500 years to decompose. As it ages, tiny pieces break off. Physical and chemical processes are known to break them down, including when exposed to sunlight or when waves grind bits of plastic against rocks, beaches or other obstacles floating in the ocean.
The researchers aimed to investigate the potential contribution of aquatic organisms to the production of microplastics, particularly after the revelation in 2018 that Antarctic krill have the ability to break down polyethylene beads into pieces smaller than one micrometre. Baoshan Xing, a professor at the University of Massachusetts Amherst’s Stockbridge School of Agriculture, stated that they chose to study rotifers due to their specialized mouthparts which are similar to those of krill. Their goal was to test the theory that rotifers, of which there are 2,000 species globally, also possess the ability to break down plastic.
“According to Xing, the senior author of the paper, we selected rotifers as our study subject because they are found in temperate and tropical regions where human populations are present, unlike Antarctic krill which reside in sparsely inhabited environments.”
According to him, the animals confuse microplastics, which are pieces smaller than 5mm, with algae.
After subjecting rotifers from both marine and freshwater environments to various sizes of plastic, researchers discovered that they were capable of consuming microplastics as small as 10 micrometers (0.01mm). These microplastics were then broken down and released as thousands of nanoplastics into the environment. Analysis revealed the presence of polyethylene microplastics, commonly found in food containers, as well as nanoplastics in the rotifers’ bodies.
Xing stated that their work was only the initial stage. They emphasized the importance of the scientific community in assessing the potential harm of nanoplastics. They also suggested examining other organisms, both on land and in water, for the breakdown of microplastics. It is crucial to collaborate with experts in toxicology and public health to understand the impact of this widespread issue of nanoplastics on human health.
Research has indicated that nanoplastics pose a greater threat to living organisms than microplastics due to their higher abundance and reactivity.
Rotifers in Poyang Lake have the ability to generate an astonishing 13.3 quadrillion nanoparticles daily. This number is likely even higher on a global scale. These microplastics have the potential to break down into 1 quadrillion nanoplastic particles, making them more easily dispersed.
Microplastics have contaminated every corner of the planet, from the top of Mount Everest to the depths of the Mariana Trench, and research has shown they are in many humans’ blood and heart tissue and the placentas of unborn babies. They cause harm in human cells in the laboratory at levels known to be eaten by people via food.
According to Jian Zhao, who is a professor of environmental science and engineering at Ocean University of China and the main writer of the study, nanoplastics have the potential to harm living things and also act as a means for other pollutants. Additionally, he noted that the plastic’s chemical additives may be released at higher levels during and after breaking down.