While we know much of the plastic waste we generate winds up in bodies of water, what happens to it from there is still a large unknown. A new study documenting the accumulation of microplastic particles on the floor of the Mediterranean Sea has shed some new light on the issue, with the authors coming to the striking conclusion that concentrations of this material on the floor of the Med has tripled since 2000.
In recent years, we’ve seen scientists start to uncover some useful insights around how plastic behaves in the marine environment. These include studies detailing underwater avalanches that drive microplastics into the deep ocean and the discovery that deep-sea trenches can act as plastic traps. In 2020, scientists studying pollution in the Mediterranean Sea identified a hotspot with the highest concentration of microplastics ever found on the seafloor.
A separate team from Spain’s Autonomous University of Barcelona and Denmark’s Aalborg University have now published more research concerning microplastics in the Mediterranean Sea, with a focus on how they sink into the seafloor, and what happens when they do.
The team collected a sediment core from the western Mediterranean Sea and used advanced imaging technology to study particles as small as 11 micrometers. This enabled the scientists to fill in important details around the accumulation of small microplastics in marine sediment, and understand how they are potentially altered after becoming embedded in the material.
In fact, the team found that the microplastics remain preserved in the seabed once they reach it. The scientists say the lack of degradation may be due to a lack of erosion, oxygen or light.
"The process of fragmentation takes place mostly in the beach sediments, on the sea surface or in the water column,” said study author Patrizia Ziveri. “Once deposited, degradation is minimal, so plastics from the 1960s remain on the seabed, leaving the signature of human pollution there.”
The scientists were able to piece together a timeline of plastic pollution in the seabed, and say the amount of microplastics has tripled since 2000, and that the nature of plastics building up in this hotspot mirrored global production and use of plastics between 1965 and 2000.
"This has allowed us to see how, since the 1980s, but especially in the past two decades, the accumulation of polyethylene and polypropylene particles from packaging, bottles and food films has increased, as well as polyester from synthetic fibers in clothing fabrics," explained Michael Grelaud, study author.
The research was published in the journal Environmental Science and Technology.
