1. Summary
Marine debris, mostly consisting of plastic, is a global problem,
negatively impacting wildlife, tourism and shipping. However,
despite the durability of plastic, and the exponential increase
in its production, monitoring data show limited evidence of
concomitant increasing concentrations in marine habitats. There
appears to be a considerable proportion of the manufactured
plastic that is unaccounted for in surveys tracking the fate
of environmental plastics. Even the discovery of widespread
accumulation of microscopic fragments (microplastics) in oceanic
gyres and shallow water sediments is unable to explain the
missing fraction. Here, we show that deep-sea sediments are
a likely sink for microplastics. Microplastic, in the form of
fibres, was up to four orders of magnitude more abundant (per
unit volume) in deep-sea sediments from the Atlantic Ocean,
Mediterranean Sea and Indian Ocean than in contaminated seasurface
waters. Our results show evidence for a large and
hitherto unknown repository of microplastics. The dominance of
microfibres points to a previously underreported and unsampled
plastic fraction. Given the vastness of the deep sea and the
prevalence of microplastics at all sites we investigated, the deepsea
floor appears to provide an answer to the question—where is
all the plastic?