Think of ocean plastic and you may picture bottles and bags bobbing on the waves, slowly drifting out to sea. Yet the reality is more complex and far more persistent. Even if we stopped all plastic pollution today, our new research shows that fragments of buoyant plastic would continue to pollute the ocean's surface for more than a century. These fragments break down slowly, releasing microplastics that sink through the water column at a glacial pace. The result is a "natural conveyor belt" of