Human Footprint in the Abyss, 30 Year Records of Deep-Sea Plastic Debris
Authors: Sanae Chiba, Hideaki Saito, Ruth Fletcher, Takayuki Yogi, Makino Kayo, Shin Miyagi, Moritaka Ogido, Katsunori Fujikura
DOI / Source: https://doi.org/10.1016/j.marpol.2018.03.022
Date: 20 March 2018
Reading level: Intermediate
Why This Matters for Freedivers
Freedivers spend time in the ocean’s “front yard,” but this paper shows that our everyday plastic habits reach the ocean’s deepest “back yard” too—down to trench depths. It’s a strong reminder that protecting the underwater world isn’t only about reefs and beaches; the deep sea is being impacted as well, and single-use plastic is a major part of it.
Synopsis
This study tackles a haunting question: how far has human plastic reached into the ocean? Not just offshore or at the surface—but all the way down to the deep seafloor, including the deepest trenches.
The authors used a large long-term record from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Their Global Oceanographic Data Center created a “Deep-sea Debris Database” that contains photos and video records from deep-sea submersibles and ROVs dating back to 1983. From 5,010 dives in the database, they counted 3,425 man-made debris items on the seafloor.
Plastic was the most common category: more than a third of all debris was macro-plastic, and most of that plastic was single-use items like bags, bottles, and packaging. Even more striking: in the very deep areas (below 6,000 m), plastic made up over half of all debris seen, and the plastic there was overwhelmingly single-use.
The deepest plastic record was a plastic bag at 10,898 m in the Mariana Trench—essentially the deepest place on Earth’s seafloor. The paper also reports that deep-sea organisms were visible with plastic in a meaningful fraction of images, including cases where plastic bags were entangled around animals and even found in chemosynthetic communities (rare ecosystems that depend on chemical energy rather than sunlight).
For a subset of dives where the team could estimate the survey area, they calculated plastic densities on the deep seafloor in the western North Pacific ranging roughly from tens to hundreds of items per square kilometer at depths of about 1,000–6,000 m. The broader message is simple and unsettling: plastic pollution is not just a coastal or surface problem. Land-based human activity has left a measurable footprint in the abyss, even far from shore.
The authors end with a call for better global monitoring and data sharing—treating deep-sea plastic pollution as something that should be tracked consistently, like other essential ocean health indicators—because you can’t manage what you don’t measure.
Abstract
This study reports plastic debris pollution in the deep-sea based on the information from a recently developed database. The Global Oceanographic Data Center (GODAC) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) launched the Deep-sea Debris Database for public use in March 2017. The database archives photographs and videos of debris that have been collected since 1983 by deep-sea submersibles and remotely operated vehicles. From the 5010 dives in the database, 3425 man-made debris items were counted. More than 33% of the debris was macro-plastic, of which 89% was single-use products, and these ratios increased to 52% and 92%, respectively, in areas deeper than 6000 m. The deepest record was a plastic bag at 10898 m in the Mariana Trench. Deep-sea organisms were observed in the 17% of plastic debris images, which include entanglement of plastic bags on chemosynthetic cold seep communities. Quantitative density analysis for the subset data in the western North Pacific showed plastic density ranging from 17 to 335 items km−2 at depths of 1092–5977 m. The data show that, in addition to resource exploitation and industrial development, the influence of land-based human activities has reached the deepest parts of the ocean in areas more than 1000 km from the mainland. Establishment of international frameworks on monitoring of deep-sea plastic pollution as an Essential Ocean Variable and a data sharing protocol are the keys to delivering scientific outcomes that are useful for the effective management of plastic pollution and the conservation of deep-sea ecosystems.