Plastic is travelling all the way along the Antarctic food chain, starting with tiny shrimp-like krill at the bottom and ending up in blue whales at the top, a study finds.
Researchers at the British Antarctic Survey found microplastics in every sample they took of krill and salps, a gelatinous invertebrate that looks a bit like a jellyfish and is another key food source at the bottom of the food chain.
Nylon was the most common form of plastic, with tiny fragments from clothing, tyres, fishing gear and ropes found in 60 per cent of krill and salps analysed in the Antarctic Ocean, according to the study, published in the journal Royal Society Open Science.
Although Antarctic krill have been found to ingest microplastics in the lab, this provides the best evidence yet that they – and other zooplankton – are absorbing them in the real world.
Antarctic krill and salps are critical to the diet of much of the Southern Ocean, or Antarctic Ocean’s marine wildlife. Krill is the main food source for whales, penguins, and seals whilst salps are eaten by some fish and larger sea birds.
“Evidence of microplastic consumption in two very high abundance species of the Southern Ocean is concerning. Both of these species are an integral part of the Southern Ocean ecosystem, and we don’t yet fully understand the impact microplastics will have in this environment,” said lead researcher, Laura Wilkie Johnston, a marine biologist at BAS.
The researchers said that because food chains in the Antarctic were short, it is “highly likely” that microplastics would be passed on from the krill to larger predators such as whales, penguins, and seals.
It is also possible some of the plastic could end up on the dinner plate in fish such as cod and mackerel caught in the Ocean, scientists said.
A study published by Stanford University in November found that blue whales ingests the most plastic, at an estimated 10 million pieces per day as they feeds almost exclusively on krill.
This found the whales predominantly feed 50 to 250 meters below the surface, a depth that coincides with the highest concentrations of microplastic in the open ocean.
The Krill and salp samples were collected onboard the research ship RRS James Clark Ross on two research missions off the Northern tip of the Antarctic Peninsula in 2016 and near the island of South Georgia in 2018.
“Microplastics were extracted from both species with plastic microfibres most common. One of the largest sources of these fibres is shedding from clothing during washing and drying,” Emily Rowlands, a marine biologist at BAS, said.
“We have already seen the harmful effects that plastic ingestion can have on Antarctic zooplankton in the lab. In this study we show how these animals are vulnerable to plastic in their natural habitat.”
Clara Manno, a pelagic marine ecologist at BAS, and lead scientist on the project, said: “In addition to being important food sources in the Antarctic marine ecosystem, krill and salps play an important role in slowing down climate change.
“The Southern Ocean is a hugely important carbon sink and these animals play an integral part transferring atmospheric CO2 into the deep oceans. Interactions with microplastics have the potential to interfere with the amount of carbon these organisms can take down and trap in the deep ocean.”