Microplastic Pollution in Antarctica: A Growing Problem

Sunday - April 14 2024, 10:49 UTC - 9 months ago

A recent study reveals that microplastic pollution is a growing problem in Antarctica, particularly in the remote Weddell Sea. The study found significant concentrations of microplastics in offshore samples and suggests that ocean currents and melting ice may play a role in their distribution. Limited sampling methods and insufficient equipment hinder deeper analysis of microplastics in the region. It is still unknown how microplastics reach Antarctica and whether they can ever leave. The strong Antarctic Circumpolar Current and global ocean currents are key factors in the presence of microplastics in this remote and pristine region.

It's not the first study on microplastics in Antarctica that researchers from the University of Basel and the Alfred-Wegener Institute (AWI) have conducted. However, data analysis from a spring 2021 expedition reveals that environmental pollution from these tiny plastic particles is a bigger problem in the remote Weddell Sea than was previously known.

The total of 17 seawater samples all indicated higher concentrations of microplastics than in previous studies. "The reason for this is the type of sampling we conducted," says Clara Leistenschneider, doctoral candidate in the Department of Environmental Sciences at the University of Basel and lead author of the study.

The current study focused on particles measuring between 11 and 500 micrometers in size. The researchers collected them by pumping water into tanks, filtering it, and then analyzing it using infrared spectroscopy. Previous studies in the region had mostly collected microplastic particles out of the ocean using fine nets with a mesh size of around 300 micrometers. Smaller particles would simply pass through these plankton nets.

The results of the new study indicate that 98.3 percent of the plastic particles present in the water were smaller than 300 micrometers, meaning that they were not collected in previous samples. "Pollution in the Antarctic Ocean goes far beyond what was reported in past studies," Leistenschneider notes. The study appears in the journal Science of the Total Environment.

The individual samples were polluted to different extents. The offshore samples, which were collected north of the continental slope and the Antarctic Slope Current, contained the highest concentrations of microplastics. The reasons for this are not conclusively known. It may be that the ice that tends to form near the coast retains the tiny plastic particles, and they are only released back into the water when the ice melts. It could also be the case that ocean currents play a role. "They might work like a barrier, reducing water exchange between the north and south," suggests Gunnar Gerdts from the AWI in Heligoland, Germany.

What is certainly true is that ocean currents are an important factor and the subject of many open questions in the field. So far, the researchers have only examined water samples from the ocean surface, but not from lower depths. This is primarily due to limited time on the ship expeditions for taking samples and to equipment with insufficient pumping capacity. "It would nonetheless be revealing to analyze such data, since the deep currents differ greatly from the surface currents and thermohaline circulation leads to exchange with water masses from northern regions," Leistenschneider says.

It is also still unclear how the microplastics make their way to the Weddell Sea in the first place and whether they ever leave the region. The strong Antarctic Circumpolar Current, which flows all the way around the Antarctic Ocean at a latitude of about 60 degrees south, might prevent their departure. The researchers are also not yet able to say conclusively where the microplastics originate.

Global ocean currents and the changing climate have the potential to transport microplastics to Antarctica, a remote and pristine location. The increasing presence of these tiny plastic particles in the Weddell Sea highlights the urgent need for global solutions to address microplastic pollution.