This creature is changing the global aquatic ecosystem! There are more than 900 per liter of water in Poyang Lake.

Plastic pollution is changing the global aquatic ecosystem. Previously, the discovery that rotifers in Poyang Lake produce plastic particles shocked the world!

Poyang Lake

According to a study published in the top international academic journal Nature Nanotechnology, rotifers in seawater and freshwater can ingest and decompose microplastics, and then generate nanoplastic particles for excretion. Taking Poyang Lake as an example, according to research data, rotifers can produce a total of 133 trillion nanoplastic particles in Poyang Lake every day. This astonishing data immediately aroused widespread attention and discussion from all walks of life, and people's curiosity about rotifers as a creature reached its peak.

Rotifer

From Antarctic krill to rotifers

So how did researchers pay attention to the relationship between rotifers and plastic pollution? This story started with a study in 2018.

At that time, Xing Baoshan, a professor at the University of Massachusetts in the United States who had been engaged in microplastic research for many years, saw a paper about "Antarctic krill can ingest microplastics and grind them into nanoplastics with their mandibles (krill's chewing organ)", which inspired him to have new scientific research ideas.

Antarctic krill

"Since Antarctic krill, a creature living in the remote polar regions, can 'decompose' microplastics, are there also widespread creatures in our daily lives that can produce the same effect, thereby affecting the content of nanoplastics in the environment?" Driven by this idea, Xing Baoshan collaborated with Professor Zhao Jian of the Ocean University of China to begin studying this issue, and their research object was rotifers.

Rotifers are common zooplankton widely distributed in surface waters around the world, most of which are no longer than 0.5 mm. In Poyang Lake, my country's largest freshwater lake, for example, there are more than 900 rotifers per liter of lake water. And, like Antarctic krill, they have a unique chewing device that can ingest and decompose various types of plastics, including polyethylene (PE) and polyvinyl chloride (PVC). The researchers observed two types of rotifers, Brachionus plicatilis and Brachionus calyciflorus, which can ingest large amounts of plastics smaller than 10 microns (which is similar to the size of their daily food), and occasionally eat some plastics as large as 20 microns, but they can't eat anything larger than that.

Rotifers affect the world's aquatic ecology

So how do rotifers excrete nanoplastic particles into the lake water?

The researchers observed under a microscope that after the rotifers ate the microplastics, many rough plastic particles of different sizes appeared in their digestive tracts, among which the number of nano-scale plastic particles was far greater than that of micro-scale ones. It can be seen that the tooth-like structure in the rotifer's chewing organ "picked" these plastic fragments from the surface of the microplastics little by little by grinding. Finally, the fragmented microplastics will be discharged from the rotifer's body and return to the lake water, eventually forming a huge number of plastic particles.

Microplastics ingested by rotifers (green pellets) and nanoplastics produced by grinding (green dots)

Take Poyang Lake as an example. The area of ​​Poyang Lake is about 3,690 square kilometers. Literature shows that on average, each liter of Poyang Lake water contains about 20.2 microplastics with a diameter of 50 to 500 microns. Assuming that all rotifers live in lake water no deeper than 5 meters, according to the data of this study, after 4 hours of rotifers being placed in water containing microplastics, an average of 131 nanoplastic particles will be generated for each microplastic particle. So, in one day, the rotifers in the entire Poyang Lake can produce a total of 133 trillion nanoplastic particles.

It is worth mentioning that the researchers also collected samples of rotifers of different species from Shuyuan Reservoir, Baisha River, Dagu River and Jiaozhou Bay in Qingdao, Shandong. As a result, microplastics with a size of 3 to 30 microns were detected in the rotifers at all sampling points. In addition, researchers also found that areas with high abundance of microplastics around the world, especially in East Asia and Europe, are also areas with the most rotifers, and there is a high degree of geographical overlap between the two. Moreover, the content of microplastics and rotifers in many surface waters on the earth is much higher than that in Poyang Lake. Literature shows that there are about 500 microplastics per liter of Yellow River water, and at the mouth of the Atiyar River in India, there are about 10,133 rotifers per liter of river water.

The global distribution of rotifers (left) and microplastics (right)

Under the influence of rotifers, the microplastic pollution in the ocean and lakes is much greater than we imagined. Due to the large specific surface area of ​​microplastics, they are easy to absorb heavy metals and organic pollutants in freshwater environments. Once these pollutants enter the food chain after being absorbed by microplastics, they can be biomagnified to a higher level, which will have a great impact on human health.

Poyang Lake, as China's largest freshwater lake, is not an isolated case. We may have greatly underestimated the role of rotifers and other related organisms in this global plastic pollution. And humans still have a long way to go to save the ecological environment of lakes, oceans, etc.