New Study Tracks Trash Found at the Ocean's Depths
While deep-ocean exploration is responsible for ground-breaking discoveries, it is also unmasking the true scale of our impacts in the deep ocean. Marine debris is a growing problem, and a new study has shown that even unexplored, remote and protected areas of the central and western Pacific deep ocean are not immune from our touch.
Coordinated deepwater exploration from 2015 to 2017 via remotely operated vehicle expeditions conducted onboard NOAA Ship Okeanos Explorer and the Schmidt Ocean Institute’s Research Vessel Falkor enabled new insights into the status of deep-sea marine debris. These expeditions included exploration of sites within U.S. protected areas and monuments, Exclusive Economic Zones of other countries, international protected areas, and areas beyond national jurisdiction.
Metal, glass, plastic, rubber, cloth, fishing gear and other debris were encountered during 17.5% of the 188 dives reviewed, at depths between 150 and 6,000 meters. While this percentage may seem low, in some areas such as off American Samoa, the densities of debris were as high as 196-1,961 items per square kilometer. This patchy distribution is likely influenced by depth, geological features such as seamounts, the proximity to areas with dense human populations, and past conflict in the region, with 5.2% of debris observed consisting of bullets, bombs and other war-related items.
Of the debris observed, 39.13% were directly impacting deep-sea life, including corals entangled with fishing gear. However, not all interactions appeared to be negative; some animals used debris for shelter or as substrate to attach to. Additionally, as these observations were only of debris larger than 2 centimeters in size, there are likely many unseen impacts, such as from microplastics and chemicals leaching out of debris.
The naturally slow biological and chemical processes operating at depth, coupled with the types of materials that are used commercially, suggest that debris is likely to persist in the deep ocean for long periods of time, ranging from hundreds to thousands of years, making these results quite alarming, especially as use of the deep ocean is increasing.
This study serves as a reminder that we need to take steps to reduce the flow of debris into the marine environment through working to stem the debris tide at point sources, reverting to a circular economy, innovating away from single use materials and ultimately consuming less.