Researchers Discover the Highest Concentration of Microplastics Ever Recorded on the Seafloor
Fri, December 3, 2021

Researchers Discover the Highest Concentration of Microplastics Ever Recorded on the Seafloor


Between 1955 and 2015, the worldwide population experienced annual growth at an average rate of 1.68%. As of April 2019, the population across the world reached 7.7 billion people, higher than that at the end of the Great Famine of 1315–1317 and the Black Death in 1350 (nearly 370 million people). This continuous increase has brought a tremendous rise in the amount of waste generated by people, which has led to increasing amounts of plastic pollution.

How Dangerous Are Microplastics?

Plastic wastes eventually undergo degradation by natural processes, forming tiny plastic fragments called microplastics. Microplastics are plastic particles measuring five millimeters in size down to one micrometer. While it’s not yet clear just how dangerous they are, marine species and even humans can absorb them unknowingly. A 2019 study published in Springer Link showed an increase in the frequency and quantity of plastic ingested by animals. At the same time, their presence in table salts, potable water, and human excreta has also been reported.

Previous reports revealed that humans produce around 400 million tons of plastic every year. Most types of plastic take several hundred years to completely degrade. As a result, we can expect a massive increase in the amount of microplastic pollution in the environment over the next few decades. More and more researchers are studying microplastics as they try to understand their impacts. According to The Guardian, a British daily newspaper, there are concerns that microplastics can accumulate toxic chemicals and that the tiniest microplastics could enter the bloodstream.

“Given their pervasive and persistent nature, microplastics have become a global environmental concern and a potential risk to human populations,” Rachel Hurley from the University of Manchester and colleagues said in their report.

According to, an internet news portal that provides the latest news on science, researchers use several different methods to analyze samples for microplastic. Thermal analysis paired with gas chromatography and mass spectrometry, for instance, is employed to determine the quantity and types of plastic particles and additives that might be present. Recent studies show that microplastics can now be found almost everywhere, from rivers to seas. These plastic particles are even present at the bottom of the world’s oceans. 



The Seafloor is Littered in Microplastic

Less than 1% of more than 10 million tons of plastic that enter the world’s oceans every year stays on the surface. Researchers at the University of Bremen, IFREMER in France, the universities of Manchester and Durham, and the National Oceanography Centre in the UK decided to know what happens to the remaining 99%. They found out that microplastics (smaller than 1mm) are being concentrated in specific locations on the ocean floor by powerful bottom currents. 

According to the BBC, an operational business division of the British Broadcasting Corporation responsible for the gathering and broadcasting of news and current affairs, the researchers found up to 1.9 million plastic pieces per square meter in sediments from the bottom of the Mediterranean, near Italy. These particles likely came from larger objects that had broken down over time and fibers from clothing and other synthetic textiles. This discovery is the highest concentration of microplastics ever recorded on the seafloor, according to the team.

"Almost everybody has heard of the infamous ocean 'garbage patches' of floating plastic, but we were shocked at the high concentrations of microplastics we found in the deep seafloor. We discovered that microplastics are not uniformly distributed across the study area; instead, they are distributed by powerful seafloor currents which concentrate them in certain areas,” lead study author Dr. Ian Kane of the University of Manchester said in the press release.

The researchers collected sediment samples from the seafloor of the Tyrrhenian Sea (part of the Mediterranean Sea) and combined these with calibrated models of deep ocean currents and detailed mapping of the seafloor. The microplastics were then transferred to the laboratory and were separated from sediment. The team was able to determine the plastic types using infra-red spectroscopy. The information gathered in this analysis helped show how ocean currents control the distribution of microplastics on the seafloor. 

Co-author Dr. Mike Clare of the National Oceanography Center said that studies of seafloor currents can help them connect microplastic transport pathways in the deep-sea and find the 'missing' microplastics. However, the findings suggest a much broader problem: deep-sea currents carry plastics to microplastic "hotspots" that may also be deep-sea ecosystems rich in biodiversity. This includes breeding zones for fish, sponges, sea cucumbers, corals, and other creatures.



According to EcoWatch, a leading environmental news site engaging millions of concerned individuals every month, there’s a possibility that these microplastics may be concentrating in important deep-sea ecosystems since these currents also distribute oxygen and nutrients. Roland Geyer, a professor of industrial ecology at the Bren School of Environmental Science and Management at the University of California at Santa Barbara, said that this study can be used to understand how plastics enter the oceans since we still have a very poor understanding of how much total plastic has accumulated in the oceans. 

"Many scientists now think that most of the plastic is likely to be on the ocean floor, but the water column and the beaches are also likely to contain major quantities. We really should all be completely focused on stopping plastic from entering the oceans in the first place,” Geyer said. 

While this study provides us with more information about microplastics, a lot still needs to be discovered. In 2019, the World Health Organization (WHO) called for a further assessment of microplastics in the environment and their potential impacts on human health, following the release of an analysis of current research related to microplastics in drinking water. Dr. Maria Neira, the director of the Department of Public Health, Environment and Social Determinants of Health at WHO, said that we urgently need to know more about the health impact of microplastics because they are everywhere, even in our drinking water. 

“Based on the limited information we have, microplastics in drinking water don’t appear to pose a health risk at current levels. But we need to find out more. We also need to stop the rise in plastic pollution worldwide,” Neira said.