Small plastic pellets or packing material of various colors may look like tiny shrimp or fish to birds. At least 162 marine species have been reported to have eaten plastic debris. When an animal eats plastic, the best case scenario is that the bulk leads them to feel less hungry, which leads to malnutrition. They usually starve to death. In some cases, certain plastics may cause internal injuries which kill the animal.
Entanglement is the other most common cause of marine harm.
Discarded fishing nets or similar plastic lines, as well as six-pack rings and plastic bags easily tangle even larger marine animals. When they become entangled, they may get permanently caught in the debris. They may be injured as they try to free themselves and their injuries can cause infections. Either way, they are often killed because either they suffocate or because they cannot escape predators. In one year, one million seabirds and one hundred thousand other marine animals die from entanglement.