Microplastics have been detected in the sea ice of Antarctica, where krill is a food source. Scientists believe this is the first time.
Microplastics have previously been discovered in Antarctica's surface waters, sediments and snow, but the new discovery could mean that the region's krill, which feed on algae from sea ice, may be more exposed to plastic.
Some 96 pieces of plastic less than 5mm wide were found in an analysis of the ice core that was drilled in 2009 and had been stored in Hobart, Tasmania.
The study found 14 different types of plastic, and on average around 12 pieces of plastic were found per liter of water.
Anna Kelly, from the Institute for Marine and Antarctic Studies at the University of Tasmania, was the lead author of the study, published in the Marine Pollution Bulletin.
Kelly said: "The remoteness of the Southern Ocean has not been enough to protect it from plastic pollution, which is now present in all the world's oceans."
According to the scientist, the concentrations found in the Antarctic ice core were slightly lower than a previous study that found microplastics in Arctic sea ice.
She said: “The microplastic polymers in our ice core were larger than those in the Arctic, which may indicate local sources of pollution because plastic takes less time to break down into smaller fibers than if they are transported long distances in ocean currents. ”.
"Local sources could include clothing and equipment used by tourists and researchers, while the fact that we also identified varnish fibers and plastics commonly used in the fishing industry suggests a maritime source," he added.
Associate Professor Delphine Lannuzel, also from IMAS and a co-author of the study, is a sea ice chemist who helped drill the core about two kilometers offshore in 2009.
The core was taken from "fast ice", ice that forms around the coast and is not mobile, unlike pack ice. The nucleus analyzed was approximately 1.1 m long and approximately 14 cm wide.
Lannuzel said that when the researchers analyzed the core, they found that the plastics were surrounded by algae that had grown on the ice.
“Sea ice is habitat for key foraging species,” he said, adding: “Krill defines everything else in the food chain and depends on sea ice algae for growth. When you now think that sea ice algae are associated with plastics, you can think of the bioaccumulation of plastics in krill and in whales. "
There was a higher concentration of plastic particles at the bottom of the ice core.
Lannuzel said that much study is still needed to understand the impact of plastics on species that depend on sea ice and that it was not known whether the toxicity of plastics was affected by processes in the guts of krill and other species, including the whales that feed on krill.
Kelly said: “Instead of sinking to the depths of the ocean, the entrapment of microplastics in Antarctic sea ice allows them to persist longer near the surface of the sea.
He added that krill was "a key species in the ecosystems of the Southern Ocean" and that it was vital for marine predators at the top of the food chain.
"It is worth noting that the plastic pollution of western Antarctic sea ice may be even greater than in our eastern ice core, as the Antarctic peninsula is home to most of the continent's tourism, research stations and shipping traffic." , Hill.