Effects on the animal world
Effects on the animal world
Plastic in bodies of water has a variety of effects on the animal kingdom. Plastic has become a fixed part of the natural habitat. Several species of animal have learned to use this material for their own purposes. But in most cases the consequences of encountering plastic are negative, and represent a major threat both to individual animals and to the ecological system as a whole.
Death caused by «ghost nets»
Fishing nets and lines can become deadly traps for marine creatures. Fish, sea mammals and turtles become entangled in the «ghost nets» and suffocate or starve. For shipping, too, these nets, which often form gigantic clumps, represent a serious hazard, as they are not visible on the surface of the water. Every year collisions or entangled propellers cause damage amounting to millions of euros to the sea transport and fishing industries.
Plastic as food
Many animals ingest plastic with their food. While all kinds of animals that feed on plankton also unintentionally ingest microplastic, birds and turtles often deliberately eat pieces of plastic, as they mistake them for food. Depending on the form of the animals’ gullets and stomachs and the way they function the indigestible pieces cannot be excreted, leading to the animals starving with full stomachs, choking, or suffering internal injuries (perforation or laceration of the intestinal walls.)
Plankton-eating organisms ingest microplastic along with their natural food. Studies of water samples taken from the North Pacific have shown that in the upper seawater column there is, at places, 46 times as much plastic as plankton.
Hundreds of tons in birds’ stomachs
According to Jan van Franeker, researcher at the IMARES Institute, migratory birds also function as transformers and transporters of plastic: three-quarters of the plastic in the stomach of a fulmar is ground down and excreted elsewhere. The scientist reckons that in this way the birds distribute hundreds of tons of plastic worldwide and process it into microplastic.
Image right: The contents of the small can on the right were found in the stomach of a fulmar and represent the average amount of plastic that a fulmar in the most heavily polluted area of the North Sea carries with it. This plastic weighs 0.6 grams. In the dish on the left is the corresponding amount calculated according to the average weight of a human being.
Animals find plastic practical, too
A number of species of animals and plants benefit from the new material: they develop new ways of using plastic products. For instance birds use plastic bands to build their nests and hermit crabs employ parts of bottles as their shells. Mussels and corals settle on buckets, pipes and other objects that have sunk to the bottom of the sea.
Invasive species threaten ecological systems
A special new way in which organisms use pieces of plastic is known as «hitch-hiking». To reproduce certain kinds of algae and plankton depend on floating material on which to lay their eggs. Previously they used vegetable material that decayed after a short time. Ever since large numbers of floating pieces of plastic became available and can be transported by currents across great distances, they use plastic as a raft and means of transport. This means that these species can travel previously inconceivable distances to reach new habitats, where they pose a massive threat to the existing ecological balance.