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Distribution of microplastics in bathyal- to hadal-depth sediments and transport process along the deep-sea canyon and the Kuroshio Extension in the Northwest Pacific

Marine Pollution Bulletin 2023 42 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Masashi Tsuchiya, Tomo Kitahashi, Ryota Nakajima, K. Oguri, Kiichiro Kawamura, Akimu Nakamura, Kengo Nakano, Yosaku Maeda, Masafumi Murayama, Sanae Chiba, Katsunori Fujikura

Summary

Researchers mapped microplastic distribution from shallow to ultra-deep ocean sediments in the Northwest Pacific, including Sagami Bay and areas beneath the Kuroshio Extension current. The study found the highest microplastic concentrations in abyssal stations and suggests two distinct transport pathways: land-sourced microplastics move to hadal depths via turbidity currents along submarine canyons, while ocean-surface microplastics sink directly to the abyssal plains below.

Study Type Environmental

Understanding microplastic (MP) behavior in oceans is crucial for reducing marine plastic pollution. However, the complex process underlying MP transportation to the deep seafloor remains unknown despite the deep sea being considered its major sink. We focused on MP distribution in Sagami Bay (adjacent to highly populated areas of Japan), the plate triple junction connected through the Sagami Trough, and the abyssal plain immediately below the Kuroshio Extension. We observed the highest number of MPs in the abyssal stations, more than previously reported. The polymer types and aspect ratio of MPs in the abyssal stations significantly differed from those in the bathyal/hadal stations. The study suggests that MPs accumulated in the open ocean surface layer sink to the abyssal plains immediately below it, while MPs from land sources accumulate in the bathyal depth and are transported to the hadal depth near the coast through turbidity currents along the submarine canyon.

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