Blue whales found to swallow 10 million microplastic pieces daily

  • Researchers studied three types of baleen whales off the US Pacific coast and found they are ingesting up to 43.5kg of plastic every day
  • Scientists are still examining the long-term effects of swallowing plastic waste on the animals
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A new study found that blue whales may swallow up to 43.5 kg of plastic every day. Photo: Shutterstock

As Earth’s largest animals, blue whales are mighty big eaters, gulping tonnes of food each day. They also now are ingesting huge amounts of plastic, according to scientists, due to the alarming volume of tiny particles of pollution choking the oceans.

Researchers on Tuesday presented an estimate of the number of microplastics ingested by three species of baleen whales – blue, fin and humpback – off the US Pacific coast, detailing an issue posing uncertain health concerns for these marine mammals.

As baleen whales, these species are filter-feeders. They strain food, including shrimp-like crustaceans called krill and other small prey, from the seawater using baleen plates in the mouth made of keratin, the substance found in people’s fingernails.

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Blue whales, according to the study, may swallow roughly 10 million microplastic pieces daily, or up to about 43.5kg of plastic. For fin whales, whose main prey is also krill, the estimated daily tally is about 6 million microplastic pieces, or up to 26kg of plastic.

Some humpback whales specialise in krill and some favour eating small schooling fish. Krill-favouring humpbacks, according to the study, may ingest about 4 million microplastic pieces (up to 17kg of plastic) daily, while those favouring fish may take in a much smaller amount, roughly 200,000 pieces.

“In the moderately polluted waters off the US West Coast, baleen whales may still be ingesting millions of microplastics and microfibres per day,” said Stanford University marine biologist Matthew Savoca, a co-author of the study published in the journal Nature Communications.

Humpback whales may swallow up to four million pieces of microplastics daily. Photo: Shutterstock

“Also we find that the vast majority – 99 per cent – is via prey that has previously ingested plastic and not from the water they filter,” Savoca added.

The study illustrated how baleen whales may be at an elevated risk for microplastic ingestion as a result of their mode of feeding, the quantity of their food intake, and their habitat overlapping with polluted areas, such as the California Current that flows south along North America’s western coast.

Blue whales can reach a maximum of about 30 metres long, fin whales about 24 metres and humpback whales about 15 metres.

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The researchers estimated the daily microplastic ingestion by examining the foraging behaviour of 126 blue whales, 65 humpback whales and 29 fin whales using measurements from electronic tag devices suction-cupped to the animal’s back, with a camera, microphone, GPS locator and an instrument that tracks movement. They then factored in the concentrations of microplastics in the California Current.

A study published last year based on the same whales off the US West Coast showed that blue whales eat about 10-20 tonnes of krill daily, while fin whales eat 6-12 tonnes of krill and humpback whales eat 5-10 tonnes of krill or 2-3 tonnes of fish.

The new study found that the whales primarily feed at depths of 50–250 metres, coinciding with the highest measured microplastic concentrations in the open-ocean ecosystem.

A close-up of microplastics, which can be found in large amounts in the ocean. Photo: Shutterstock

Microplastics are particles of plastic debris – less than 5mm long – arising from the disposal and breakdown of various consumer products and industrial waste, with their concentrations in the oceans mounting in recent decades. The potential health effects on the whales from ingesting it is not well understood.

“While this was not the focus of our study, other research has shown that if plastics are small enough they can cross the gut wall and get into internal organs, though the long-term effects are still unclear. Plastics can also release chemicals that are endocrine disrupters,” said marine biologist Shirel Kahane-Rapport of California State University, Fullerton, lead author of the study.

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