German researchers say they have found proof of the damaging longevity of modern plastics.
Not only can they survive virtually unscathed deep below the sea, they can disrupt the surrounding environment while they lie there.
The research vessel SONNE was 815 kilometres off the coast of Peru in the eastern Pacific Ocean, working in what is known as the DISCOL Experimental Area, when it picked up several pieces of waste from the seabed at a depth of more than four kilometres.
Such finds are sadly not uncommon, but in this case the team from GEOMAR Helmholtz Centre for Ocean Research Kiel, the Max Planck Institute for Marine Microbiology and Kiel University was able to discover how long they had been there.
Among the recovered items was a plastic bag containing a Coke can, which was part of a special edition produced for the tennis Davis Cup in 1988.
“The aluminium can itself would have corroded in the deep sea, if it was not wrapped tightly inside a plastic garbage bag that preserved it,” says GEOMAR’s Matthias Haeckel. “This also indicates that the garbage bag must be of the same age.”
Another item was a curd box from a German manufacturer that was bought by a rival company in 1999, when the brand name disappeared.
As the DISCOL area is away from major routes, the researchers suspect participants on expeditions in 1989, 1992 or 1996 are likely to blame – which is an issue in itself.
Of wider concern was the condition of the items. “It turned out that neither the bag nor the curd box showed signs of fragmentation or even degradation”, says GEOMAR biochemist Stefan Krause from GEOMAR, the lead author of a paper in the journal Scientific Reports.
A scientifically most interesting finding was that the microbial community on the plastic surfaces differed from the one identified in the surrounding seafloor sediments.
“All of the species can be found in the deep-sea sediment, but apparently, larger accumulations of plastics could locally cause a shift in the ratio of the predominant species,” says Krause.
The researchers acknowledge in their paper that whether the plastic would eventually be affected is open to debate.
“However,” they write, “it is plausible that, if thermodynamically granted at all, degradation reactions will proceed at very slow speed. Consequently, plastic debris in the deep sea might be present over very long, i.e. geological, time scales.”
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