Study: Ocean plastics to be cleaned up on coasts, not at maritime garbage patch

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Marine litter (Foto: ©FotoHiero /http://www.pixelio.de)

London, UK – The most efficient way to clean up ocean plastics and avoid harming ecosystems is to place plastic collectors near coasts, according to a new study. The new analysis by Dr Erik van Sebille and undergraduate physics student Peter Sherman from Imperial College London suggests that targeting the Great Pacific garbage patch is not the most efficient way to clean up the oceans.

Dr van Sebille, from Imperial’s Grantham Institute, and Sherman used a model of ocean plastic movements to determine the best places to deploy plastic collectors to remove the most amount of microplastics, and to prevent the most harm to wildlife and ecosystems. They found that placing plastic collectors like those proposed by The Ocean Cleanup project around coasts was more beneficial than placing them all inside the patch. For a ten-year project between 2015 and 2025, the team found that placing collectors near coasts, particularly around China and the Indonesian islands, would remove 31 per cent of microplastics. With all the collectors in the patch, only 17 per cent would be removed.

“The Great Pacific garbage patch has a huge mass of microplastics, but the largest flow of plastics is actually off the coasts, where it enters the oceans,” said Sherman. “It makes sense to remove plastics where they first enter the ocean around dense coastal economic and population centres,” added Dr van Sebille. “It also means you can remove the plastics before they have had a chance to do any harm. Plastics in the patch have travelled a long way and potentially already done a lot of harm.”

Avoiding harm to ecosystems

The pair’s model also looked at areas where microplastics overlapped with phytoplankton – microscopic floating plants that form the basic food of many ocean ecosystems. Many microplastics enter the food web in these areas as microscopic animals accidentally eat them. Running the same model for areas rich in phytoplankton came up with a similar result: The overlap was reduced by 46 per cent by placing collectors near certain coasts, whereas the overlap was only reduced by 14 per cent by placing the collectors in the patch.

“There is a lot of plastic in the patch, but it’s a relative dead zone for life compared with the richness around the coasts,” said Sherman. A recent analysis by Dr van Sebille and colleagues in Australia showed that more than 90 per cent of seabirds have swallowed plastics, and these birds are also concentrated around coasts where their food is plentiful.

The pair will refine their analysis, but say the results are clear and hope that plastic collecting projects in the future will focus on the coastlines. “We need to clean up ocean plastics, and ultimately this should be achieved by stopping the source of pollution,” said Sherman. “However, this will not happen overnight, so a temporary solution is needed, and clean-up projects could be it, if they are done well.”

The study „Modeling marine surface microplastic transport to assess optimal removal locations“ by Peter Sherman and Erik van Sebille was published in the Environmental Research Letters and can be downloaded under iopscience.iop.org.

Source: Imperial College London