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How long does marine debris stay in the environment?

Many plastics never fully break down in the environment, instead they break apart into tiny pieces called microplastics.

Many plastics never fully break down in the environment; instead, they break apart into tiny pieces called microplastics (Credit: Sustainable Coastlines Hawaii).

Huge amounts of marine debris enter the ocean and Great Lakes every year, but once our trash is in the ocean, what happens to it? How long does it last, and can we ever say that it’s gone? Unfortunately, when we talk about the amount of time something takes to break down in the marine environment (or its degradation rate), the answer isn’t simple.

Marine debris is made up of many different types of human-made materials, which all break down in different ways. This makes it difficult for us to understand how long they will last in the ocean or Great Lakes. You may hear that it takes hundreds of years for some items to degrade, but there are many factors that can cause an item to break down quickly, or not at all! For plastics, exposure to sunlight; water; microorganisms like bacteria, fungi, and algae; temperature; the amount of oxygen in the water; and the location of an item can all contribute to how it breaks down.

It’s especially difficult to understand how human-made materials, like plastics, degrade in the marine environment. Not all plastics are the same. “Plastic” is a term that describes a wide range of human-made polymers. Manufacturers use these materials to make many different products, like food and beverage packaging, plastic bags, electronics, medical devices, car parts, appliances, etc. When making plastics, chemicals (called additives) give each type different qualities, like flexibility, bright colors, and resistance to sunlight and fire. Because plastics can come in so many forms and with so many additives, it can be even more difficult to understand how long something made of plastic takes to degrade. In fact, some plastics can break into tinier and tinier pieces, and may never fully go away.