Red Sea surface waters contain little plastic

Materials World magazine
,
11 Jan 2018

The Red Sea has relatively low amounts of floating plastic debris in its surface waters due to fewer sources or faster removal, research by the King Abdullah University of Science and Technology (KAUST), Saudi Arabia, has found.

The scientists collected samples of floating plastic rubbish from 120 sites along 1500km of shoreline on the eastern margin of the Red Sea during voyages in 2016-2017. The debris was captured in plankton nets dragged slowly just below the sea surface and the fragments were then painstakingly sorted into material type and size.

Three-quarters of the collected rubbish was rigid fragments of broken objects. Plastic film, such as bags or wrapping, made up 17%, but there were only small amounts of fishing lines or nets (6%) and foam (4%).

The relatively low levels of floating plastic in the Red Sea may either be due to there being fewer sources of rubbish or its faster removal, explains doctoral student, Cecilia Martin. Not much plastic comes from the land because this coastline has few of the usual polluting contributors. ‘Usually the main source of plastic in the sea tends to be litter and mismanaged waste,’ said Martin. ‘But on this coastline, the only large human settlement is Jeddah, with a population of 2.8 million people, and little tourism, so there are few people with the opportunity to litter.’ Similarly, rivers globally provide 10-50% of discarded oceanic plastic, but because the Red Sea catchment has no permanent rivers, their contribution is negligible.

‘Instead, the winds and a few storms are most probably the main sources of plastic,’ said Martin. ‘This is reflected in our findings of proportionally higher amounts of plastic films compared to global trends.’

There is a concern, however, says Martin, about the missing plastic. The low levels of debris can be partially attributed to its removal by the extensive mangrove and coral reef systems of the area. Capture of plastics is problematic for these ecosystems.

‘Mangroves are perfect traps for macrolitter,’ said Martin. ‘At high tide, floating items reach the forest and then, as the tide drops, get stuck in seedlings and mangrove aerial roots (pneumatophores) which act as a mesh to trap them.’

Read more at: Elisa Martí et al. Low Abundance of Plastic Fragments in the Surface Waters of the Red Sea, Frontiers in Marine Science (2017). DOI: 10.3389/fmars.2017.00333