National Public Radio: The vast majority of debris in the ocean - about 75 percent of it - is made of plastic. It can consist of anything from plastic bottles to packaging materials, but whatever form it takes, it doesn't go away easily.
While plastic may break down into smaller and smaller pieces, some as small as grains of sand, these pieces are never truly biodegradable. The plastic bits, some small enough that they're called microplastics, threaten marine life like fish and birds, explains Richard Thompson, a professor...