How does plastic pollution affect marine life?

What species are most affected by marine plastic pollution?

Whales and other marine megafauna

Large marine mammals are highly vulnerable to plastic entanglement, particularly from ghost fishing gear. Fishing ropes, nets and pots that have been discarded or abandoned at sea are often made from plastic, and can trap and entangle a variety of marine life, from blue whales to small crabs. An estimated 300,000 whales, dolphins and porpoises a year die from ghost gear entanglement. Marine megafauna are also vulnerable to plastic ingestion; in 2019, one whale was found washed up with 40kg of plastic in its stomach, predominantly comprising plastic bags.

Sea turtles

Turtles often mistake plastic for food. Plastic bags look similar to jellyfish, the staple diet of leatherback turtles, and fishing nets can look like delicious seaweed. When turtles eat plastic bags, it can make them feel full, eventually leading to starvation. A recent study found that all seven species of sea turtle from the Atlantic and Pacific Oceans and the Mediterranean Sea had traces of microplastics in their gut. Sea turtles also fall victim to entanglement from six-pack rings, which can get caught around their shells and necks.

Seabirds

For millennia, seabirds have fed from the surface of the ocean, swooping down and scooping up small fish and algae. It’s no surprise, then, that seabirds are now mistaking small plastic fragments that sit on the water’s surface for food. When ingested, these small pieces of plastic can lead to starvation or suffocation. Some seabirds are able to regurgitate pieces of plastic, but petrels, for example, find this difficult. Northern fulmars are known to ingest plastic pellets and consequently, the species is now monitored as an indicator of pellet pollution levels in the North Sea. Many species of seabird have also been found feeding plastic pieces to their young. Plastic debris is said to cause the deaths of more than a million seabirds each year.

Fish and molluscs

Hundreds of fish species, including many that humans consume, have been found with traces of microplastics in their bodies. In a study summarising over 100 research papers on fish and plastic ingestion among 500 fish species, over two-thirds had consumed plastic. Fish often mistake small plastic pieces, such as pellets, for food.

When molluscs such as mussels and oysters filter seawater to feed, they also take in human-created pollutants, including microplastics. In a recent study of mussels sourced from UK waters, 100% of samples were found to contain microplastic pieces.