Scientists Discover Link Between Deep Sea Currents And Microplastic Hot Spots

A team of scientists has discovered the highest concentration of microplastics ever recorded on the seafloor, according to their findings published in Science yesterday. Led by Dr. Ian Kane of the University of Manchester, the team consisted of a collaboration of researchers from the University of Bremen, IFREMER, University of Durham, and the National Oceanography Centre in the U.K.

In a survey of the Tyrrhenian basin between Italy, Corsica, and Sardinia, the team found 1.9 million plastic pieces per 11 square feet of seafloor, representing the largest microplastic hot spot found to date. Their findings suggest that deep-sea currents carry the debris to microplastic hot spots, which could impact deep-sea ecosystems that are rich in biodiversity.

One of the researchers, Professor Elda Miramontes of the University of Bremen, says that these results represent a clear call to action.

"We're all making an effort to improve our safety and we are all staying at home and changing our lives — changing our work life, or even stopping work. We're doing all this so that people are not affected by this sickness. We have to think in the same way when we protect our oceans," she told BBC News.

Fish swim in the new Sea-Life Aquarium in the Olympic Park in Munich, Germany.
Getty Images | Jan Pitman

Microplastics consist of tiny fibers from clothing and other synthetic textiles, as well as fragments from larger objects that have broken down over time. They enter the ocean system via rivers when wastewater treatment plants do not filter them out properly. It is estimated that over 10 million tons of plastic enter the ocean each year, but less than 1 percent of this stays at the surface.

The goal for Dr. Kane and the team was to find out what happens to the remaining 99 percent. Their data shows that microplastics do not settle on the seafloor evenly. Instead, they are pushed together with sediment by strong deep-sea currents.

"Almost everyone has heard of the infamous 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," Dr. Kane explained.

These same seafloor currents are also responsible for distributing oxygen and nutrients. As a result, microplastic hot spots could form in important deep-sea ecosystems, posing a significant threat to the sea life living there as they accidentally consume the plastic pieces.

This study is the first to reveal a connection between deep-sea currents and microplastic distribution. Moving forward, the team's findings could promote further research into hot spots elsewhere in the world, allowing scientists to better evaluate their impact on marine life. The results also allow for the possibility of better microplastic management in the future as they show more clearly the role that seafloor currents play in how microplastics are transferred and stored in the ocean.