While many different types of trash enter the ocean, plastics make up the majority of marine debris for two reasons. First, plastic’s durability, low cost, and malleability mean that it’s being used in more and more consumer and industrial products. Second, plastic goods do not biodegrade but instead, break down into smaller pieces.
In the ocean, the sun breaks down these plastics into tinier and tinier pieces, a process known as photodegradation. Most of this debris comes from plastic bags, bottle caps, plastic water bottles, and Styrofoam cups.
Marine debris can be very harmful to marine life in the gyre. For instance, loggerhead sea turtles often mistake plastic bags for jellies, their favorite food. Albatrosses mistake plastic resin pellets for fish eggs and feed them to chicks, which die of starvation or ruptured organs.
Seals and other marine mammals are especially at risk. They can get entangled in abandoned plastic fishing nets, which are being discarded largely due to inclement weather and illegal fishing. Seals and other mammals often drown in these forgotten nets—a phenomenon known as “ghost fishing.”
Marine debris can also disturb marine food webs in the North Pacific Subtropical Gyre. As microplastics and other trash collect on or near the surface of the ocean, they block sunlight from reaching plankton and algae below. Algae and plankton are the most common autotrophs, or producers, in the marine food web. Autotrophs are organisms that can produce their own nutrients from carbon and sunlight.
If algae and plankton communities are threatened, the entire food web may change. Animals that feed on algae and plankton, such as fish and turtles, will have less food. If populations of those animals decrease, there will be less food for apex predators such as tuna, sharks, and whales. Eventually, seafood becomes less available and more expensive for people.