Microplastics and synthetic particles ingested by deep-sea amphipods in six of the deepest marine ecosystems on Earth

Abstract

While there is now an established recognition of microplastic pollution in the oceans, and the detrimental effects this may have on marine animals, the ocean depth at which such contamination is ingested by organisms has still not been established. Here, we detect the presence of ingested microplastics in the hindguts of Lysianassoidea amphipod populations, in six deep ocean trenches from around the Pacific Rim (Japan, Izu-Bonin, Mariana, Kermadec, New Hebrides and the Peru-Chile trenches), at depths ranging from 7000 m to 10 890 m. This illustrates that microplastic contaminants occur in the very deepest reaches of the oceans. Over 72% of individuals examined (65 of 90) contained at least one microparticle. The number of microparticles ingested per individual across all trenches ranged from 1 to 8. The mean and standard error of microparticles varied per trench, from 0.9 ± 0.4 (New Hebrides Trench) to 3.3 ± 0.7 (Mariana Trench). A subsample of microfibres and fragments analysed using FTIR were found to be a collection of plastic and synthetic materials (Nylon, polyethylene, polyamide, polyvinyl alcohol, polyvinylchloride, often with inorganic filler material), semi-synthetic (rayon and lyocell) and natural fibre (ramie). Notwithstanding, this study reports the deepest record of microplastic ingestion, indicating that anthropogenic debris is bioavailable to organisms at some of the deepest locations in the Earth's oceans.

Keywords: hadal; marine; microfibre; microplastic; pollution; trench.

Figure 1.

Locations of the six trenches around the Pacific rim where amphipods were sampled for microplastic ingestion. The sites include the Japan, Izu-Bonin and Mariana trenches in the northwest Pacific; the New Hebrides and Kermadec trenches in the southwest Pacific and the Peru-Chile Trench in the southeast Pacific.

Figure 2.

The three species of Lysianassoidea amphipods collected from six hadal trenches around the Pacific rim. (a) Hirondellea gigas, (b) Hirondellea dubia and (c) Eurythenes gryllus. Scale bar = 10 mm. * indicates position of coxa 4.

Figure 3.

A selection of microfibre examples found within amphipod hindgut samples from 10 890 m in the Mariana Trench.

Figure 4.

(a) Percentage of amphipods with at least one ingested particle item; (b) the mean (±s.d.) number of items per individual; (c) composition of colour and type and (d) composition colour and type of particle expressed as percentage. All plotted against site (and depth), n = 10. Abbreviations for the sites are: JT, Japan Trench; IBT, Izu-Bonin Trench; MT, Mariana Trench; NHT, New Hebrides Trench; KT, Kermadec Trench; and PCT, Peru-Chile Trench.