Plastic reaches the deep sea

Plastic is everywhere; even at 7 miles deep. What was once thought of as a safe haven away from anthropogenic impacts, has been found to contain plastic. Recent research has found that the Mariana Trench, the deepest part of the ocean, contains persistent organic pollutants (POP’s) that are absorbed onto plastic.

The new study, published in Nature on 13th February 2017, examines the concentrations of persistent organic pollutants in the two deepest trenches in the oceans; the Mariana Trench in the North Pacific and the Kermadec in the South Pacific. Researchers found that crabs in the Mariana Trench contained 50 times more toxic chemicals than crabs found in the Liaohe River, one of the most polluted rivers in China.

Bits of plastic and dead animals containing POP’s sink to the bottom of the ocean. They’re then eaten by scavengers and gradually make their way up the ecosystem and food chain, where they bioaccumulate in organisms. Persistent organic pollutants are of particular concern due to their ability to disrupt the endocrine system and inability to degrade.

The study also found that POP’s were higher in the Mariana trench than the Kermadec trench. This could be because of the famed ‘Great Pacific Garbage Patch’ (see article ‘Great Pacific Garbage Patch – real or not real?’) in the North Pacific that would contribute more plastics and therefore more POP’s to the trench that lies beneath it.

It is now thought that many deep sea trenches around the world are also becoming sinks for plastics and the chemicals they contain. The presence of plastics in the deep sea is likely to rise with the increase of plastic input at the surface. This is a serious problem due to the inaccessibility of the trenches making cleaning them up virtually impossible.

Sources

Jamieson, A.J., Malkocs, T., Piertney, S.B., Fujii, T. and Zhang, Z. (2017) ‘Bioaccumulation of persistent organic pollutants in the deepest ocean fauna’, Nature Ecology & Evolution, 1, p. 0051. doi: 10.1038/s41559-016-0051.

Photo credit: Schmidt Ocean Institute

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