Microplastics in the final ocean frontier

The deep sea is classified as the portion of the ocean deeper than 200m and off the continental slope (1). The deep sea covers over half the Earth’s surface and supports an incredibly rich diversity of species (2). This remote region has largely remained out of sight out of mind, however is vulnerable to a number of anthropogenic impacts. Macroplastics are recorded extensively in the deep sea (3), and concern is mounting regarding microplastics, as these small persistent plastics represent one of the greatest threats to ecosystem functioning and services.

Worldwide distribution of microplastics is patchy and current estimates suggest lower quantities in surface waters than expected (4). Microplastics have been reported in deep-sea sediments (5), hypothesising the deep sea may be a sink for this pollutant. The ultimate fate of marine microplastics are not well understood; while numerous species are reported to ingest microplastics, currently no studies have considered whether the deep-sea benthic community is also susceptible, and if so how ingested quantities compare to upper ocean species.