Plastic pollution is a major threat to ocean ecosystems, with over 10 million metric tons of plastic entering the marine environment each year.
While surface plastics such as fishing nets and plastic bags often grab attention due to their impact on marine life, the problem extends much deeper into the ocean.
In 2019, a plastic bag was even discovered in the Mariana Trench, nearly 11,000 meters below sea level, underscoring the widespread nature of the issue.
New research explores how plastic debris accumulates in the deep ocean, specifically within underwater canyons, through the action of turbidity currents.
These turbulent flows, which are gravity-driven and move at speeds up to 20 meters per second, erode the seafloor and expand submarine canyons.
They also transport large amounts of sediment, nutrients, and pollutants, including plastics, to the deep ocean.
Dr. Yupin Yang from China’s Southern University of Science and Technology and her team used bathymetric data and video footage from submersible dives in the Qiongdongnan region of the South China Sea between 2018 and 2020.
Combining these datasets with computational fluid dynamics models, they simulated how turbidity currents interact with plastic debris across different seafloor topographies.
The research revealed that the morphology of submarine canyons plays a crucial role in the deposition of plastic litter.
Study shows that submarine canyon morphology influences plastic debris deposition patterns in the ocean.Specifically, concave scours—depressions in the canyon floor—encourage the deposition of plastics, with 88% of plastic litter accumulating in four such features in the study area.
Shear velocity, or the stress at the base of the turbulent current, was identified as the key factor controlling how and where plastics settle.
The researchers found that lower shear velocity correlated with the deposition of plastics, including plastic bags.
This study highlights the unique behavior of plastics in turbidity currents. Unlike sediments, plastics’ buoyancy allows them to travel further and faster across the seafloor.
More energetic turbidity currents can later redistribute these plastics deeper into the ocean, potentially keeping them in the environment for many years.
This finding is crucial for understanding the long-term impact of plastic pollution on deep-sea ecosystems and offers insights into potential solutions for mitigating its spread.