Plastic debris is of particular concern due to its abundance, and its persistence in the environment, which makes it a ubiquitous category of marine debris. Global production of plastics has increased considerably over the last few decades from 5 million tonnes per year in the 1960s to 280 million tonnes per year in 2011. The absolute quantity of plastic debris that enters the marine environment is, however, unknown. Sampling is typically restricted to the sea surface in coastal waters and shorelines, and temporal trends have been found to vary between regions. It is evident, however, that despite efforts to remove debris from the marine
environment, and restrictions on dumping at sea, quantities of plastic are increasing in some locations. In many areas quantities are highly variable but stable and for some debris types
there is evidence of a decrease, but it seems inevitable that since most plastics will not biodegrade, quantities in the marine environment will increase over time. . It is likely that
the lack of consistent trends in temporal data represent the movement of debris to compartments where monitoring is minimal such as deep sea sediments and offshore areas, and also the fragmentation of plastic debris into pieces smaller than those routinely sampled.