Researchers analyzed 18,000 hours of underwater video collected by MBARI's remotely operated vehicles (ROVs) over the past 22 years. Virtually every object and animal to appear in these videos is archived in MBARI's Video Annotation and Reference System (VARS).
Lead author Kyra Schlining said a fisheries study off Southern California looked at seafloor trash, but only down to 365 meters.
"We were able to continue this search in deeper water -- down to 4,000 meters. Our study also covered a longer time period, and included more in situ observations of deep-sea debris than any previous study I'm aware of," Schlining said.
Researchers focused in and around Monterey Bay and noted over 1,150 pieces of debris on the seafloor in that region alone.
About one third of the debris consisted of plastic objects. Metal objects were the second most common, about two thirds of which were aluminum, steel or tin cans. Other common debris included rope, fishing equipment, glass bottles, paper and cloth items.
In the same areas where they saw trash, researchers also saw kelp, wood, and natural debris that originated on land. They concluded that much of the trash in Monterey Canyon comes from land-based sources, rather than boats and ships.
The study found that litter was more common in the deeper parts of the canyon, below 2,000 meters (6,500 feet).
"I'm sure that there's a lot more debris in the canyon that we're not seeing," Schlining said, adding that the near-freezing water, lack of sunlight and low oxygen at those depths means there are fewer bacteria and organisms to break down the deep-sea trash, which may last for decades.