Unlike organic debris, which biodegrades, the photodegraded plastic disintegrates into ever smaller pieces right down to molecular level, once small enough it concentrates in the upper layer of the ocean and can be ingested by tiny aquatic organisms. In this way, plastic enters the food chain.
In addition larger pieces of plastic are picked up by a range of organisms:
- A study of 1.5 million Laysan Albatrosses that inhabit Midway, found nearly all to have plastic in their digestive system. Approximately one-third of their chicks die, and many of those deaths are due to being fed plastic from their parents
- Toxin-containing plastic pieces are eaten by jellyfish, which are then eaten by larger fish. Many of these fish are then consumed by humans, resulting in their ingestion of toxic chemicals, such as bisphenol A and PCBs.
- Marine plastics also facilitate the spread of invasive species that attach to floating plastic in one region and drift long distances to colonize other ecosystems.
- Large pieces of plastic kill fish, birds and turtles as the animals' digestive system cannot break down the plastic that is taking up space inside their stomachs. They subsequently die of starvation.
- Plastic make it much more difficult for animals to detect their normal sources of food. While eating their normal source of food plastic ingestion can be unavoidable.
- Research has shown that plastic marine debris affects at least 267 animal and bird species worldwide.
With an estimated 6.4 million tons of plastic dumped in the ocean annually, build-up has become a huge problem that merits serious attention.