Trashy tales from the ocean depths

Original story by Peter Hannam, Sydney Morning Herald

The accumulation of rubbish near the ocean surface is well known, such as the “Great Pacific Garbage Patch” which could extend over a region twice the size of Australia.

Ocean trash: Coke bottle located at depth of 1,727m. Source: MBARI.

Much less is known about how much trash is ending up on the ocean floor. A recent study by researchers at the US-based Monterey Bay Aquarium Research Institute probed depths as low as 4000 metres in regions stretching from Canada's Vancouver Island to the Gulf of California and west to Hawaii.

They found debris collected in more than 1000 sites, mostly where currents flow past rocky outcrops or other obstacles, often in deeper regions.

Oil drum located 2892m down, in the Monterey Canyon. Source: MBARI.

The lack of sunlight, near-freezing conditions and low oxygen levels at those depths - below 2000 metres - limit the growth of bacteria or other organisms that can break the trash down. Plastic bags and aluminium cans may last for decades.

"The most frustrating thing for me is that most of the material we saw - glass, metal, paper, plastic - could be recycled," Kyra Schlining, lead author on this study, said in a report on the institute's website.

Tyre found 868m below the surface on a ledge in the Monterey Canyon. Source: MBARI.

The cost of retrieving the rubbish meant the most cost-effective solution is to prevent the litter entering the marine environment in the first place, Ms Schlining said.