Which material forms the majority of marine debris?
Plastic constitutes most persistent marine debris by item count in many surveys because production and disposal volumes are enormous, buoyant products travel far, and polymers degrade very slowly. Bags, bottles, fishing gear, packaging, and fragments remain in coastal and open-ocean systems for years. Glass and metal also occur but are generally less abundant and may sink or corrode; organic waste decomposes much more readily. Laboratory effects must be interpreted alongside environmentally realistic concentrations, while field detection demonstrates exposure but does not alone prove causation
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology