The amount of plastic floating in the world's oceans is between 6,000 and 31,000 tonnes — an estimate that is much less than expected given current plastic-production levels.
Andrés Cózar at the University of Cadiz in Puerto Real, Spain, and his colleagues studied more than 3,000 surface-water samples collected from oceans around the world in 2011. Nearly 90% of the samples contained plastic debris, with a wide range of concentrations. The team found a lower than expected amount of plastic smaller than five millimetres in size.
The researchers think that a combination of mechanisms might explain the missing plastic: the small pieces could be sinking into the ocean interior, breaking down into even smaller, undetectable particles, or being ingested by zooplankton and small fish.
Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1314705111 (2014)