There are a few biological impacts for the animals and fish living in the ocean, as well as all other animals who take part in the food chain. Multiple species are directly affected by the plastic debris in the ocean, the most affected are the sea turtles, sea birds and marine mammals. It has been estimated that plastic marine debris affects 267 species globally. The most common threats to the marine life include ingestion and entanglement. Animals can become trapped in plastics, such as fishing gear, nets, and lines. In the worst case this can then cause death by drowning, suffocation, starvation and injuries.

Plastic can also end up in the stomachs of marine animals, as it attracts seabirds and fish. Mostly the red colored plastic is eaten by fish and birds as that equals the most to their prey. Some species consume plastic faster than others, this has to do with the prey types. For example, sea turtles often consume plastic bags that appear similar to their prey. When predators afterwards eat the fish that have consumed the plastic, the plastic enters the food chain. The ingestion of plastic may cause several problems, for example the development of internal and external wounds. The plastic can also build up in the digestive system and cause impairment of feeding capacity, and thereby reducing body weight and fat deposition. Ultimately the animal will then die due to not being able to eat. Another consequence is the decreased mobility that plastic may cause, by which the animals are less effective in avoiding predators. Below is an image of a seabird whose stomach is full of plastic.