Garbage in the sea: Whales swallow up to ten million pieces of plastic a day

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Blue whales are the largest animals in the world and filter their food from the water

Photo: Gerard Soury/Getty Images

Whales not only filter krill and small fish out of the water, but also involuntarily a lot of microplastics.

A US research team reports in the journal »Nature Communications« that just one blue whale, the largest animal on earth, eats around ten million pieces of microplastic every day.

The researchers had examined data on the distribution of microplastics and the feeding behavior of baleen whales, which include blue whales and humpback whales, off the coast of California.

Charged Prey

Plastic particles that are smaller than five millimeters are considered microplastics.

They come, for example, from car tires, synthetic clothing or packaging.

If they get into the sea, they accumulate above all in water depths between 50 and 250 meters – precisely those depths where baleen whales forage for their food.

The whales feed mainly on animal plankton and small sea creatures such as krill, which they filter out of the water through horny plates in their jaws.

However, the majority of the small marine animals contain microplastics, which the whales ingest indirectly through their contaminated prey.

Marine debris isn't just a problem for whales.

It is estimated that up to four million tons of plastic enter the sea via rivers every year.

The garbage sometimes collects in huge garbage carpets on the surface of the seas.

Over time, larger pieces of plastic are broken down into smaller and smaller particles.

Microplastics make up around 80 percent of the plastic washed into the oceans worldwide.

According to estimates, the amount of microplastics in the sea will more than double in the next 30 years.

Even the deep sea floor is contaminated with microplastics.

However, it not only swims in the sea, but can be detected almost everywhere, including in human blood.

For the current study, the researchers observed 191 marked baleen whales that were navigating the California coast between 2010 and 2019, including Monterey Bay and the Channel Islands.

Using mathematical models, the research team estimated how much microplastic a whale ingests per day.

Blue whales, which are over 30 meters long and weigh almost 200 tons, could swallow ten million microplastic parts a day, the smaller, around 15 meter long humpback whales up to four million particles.

The scientists warn that the large, contaminated amounts of food are a risk and a stress factor for the marine mammals.

They are calling for further studies to show how badly microplastics endanger the health of animals.

koe/dpa