A study concluded that the oceans pose a greater risk to the health of the world’s largest creatures than was previously thought as a single blue whale may swallow as much as 10 million pieces of plastic in a day.
These 150 tonne animals consume this vast amount of plastic in the form of microplastics which are fragments and fibres smaller than 5 mm.
The study looked at information on the feeding behaviour of 191 humpback, fin and blue whales. They were tagged and tracked as they fed off the coast of California.
Blue whales live of krill, very small shrimp-like crustaceans. Humpback and fin whales also feed off fish.
They feed by travelling at speed with their mouths open allowing them to ingest vast amounts of water and prey animals.
The Times newspaper reports that in one session of feeding a blue whale can ingest a volume of krill slurry which is as large as its own body.
The water is drained through their baleen which is a filtration system inside their mouths, and which leads to krill being left behind and digested.
These whales feed at depths normally of around 50-250 metres according to researchers from Stanford University. This happens to be where most of the ocean’s microplastics are situated.
The researchers decided that the microplastics that there ingest were inside the prey animals that they eat.
“The krill eat the plastic, and the whale eats the krill” according to Matthew Savoca, a postdoctoral scholar at Stanford’s Hopkins Marine Station in California.
Humpback whales which feed mainly on herring and anchovies ingest an estimated 200,000 pieces of micro-plastic daily but the blue whale feeding off krill ingests much more plastic at about 1 million pieces per day.
It appears that the fin whale suffers the most. They feed on both krill and fish and eat an estimated 3 million to 10 million micro-plastic pieces per day. That’s a single whale.
The scientists suspect that these numbers are even higher for whales that forage in more polluted regions such as the Mediterranean Sea.
One concern is that the large amounts of plastic makes their diet less nutritious and secondly the chemicals used to make plastics and inside these plastic particles may be toxic to whales.
It looks as though we won’t know the true effect on whales until they start falling ill and you wonder then whether it be too late. The oceans are full of micro-plastics. These tiny particles are everywhere and not only in the oceans but on land as well.
The lead researcher in this study, Shirel Kahane-Rapport said: “If patches are dense with prey but not nutritious [whales] have eaten something that is essentially garbage.”
The ingestion of plastic was first reported 50 years ago, and the reports now say that at least 1,000 species ingest plastic but the “unique concern for whales is that they can consume so much” said Savoca.