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Written summary

 of our research from August 2016 till October 2017

BTOWU research expedition, credits: Jasper Doest

Newsletter Science article


An integral part of every By the Ocean we unite expedition is sampling the waters for plastic fragments. This allows us to show the expedition members on board that small plastic fragments are pretty much everywhere while they are almost invisible from above the surface, illustrating how the problem is much larger than just the bigger bottles and bags floating around. Additionally, such measurements can be shared with scientists, giving them baseline values of plastic densities which they can use to focus their research. Scientific expeditions are very expensive and not having to use resources for such baseline measurements can give plastic research a real head start.

Throughout 2017, expedition teams have been sampling the North Sea and Wadden Sea, and even Loch Ness. Almost all samples contained plastics larger than one millimeter, the few exceptions being one sample from the Wadden Sea and both samples from Loch Ness. Especially the Loch Ness samples were interesting because it showed that such relatively isolated bodies of water can still be relatively unpolluted. Two other samples were also very interesting. One sample from the North Sea north of Cherbourg, France, and one from the Wadden Sea. Remarkably, both contained 248 fragments, our largest catches so far. The Cherbourg sample came from an area where currents seemed to bring floating debris together. Dense floating seaweed made it necessary to abort the sampling after thirty minutes and caused the sample processing to last deep into the night. The Wadden Sea sample was collected just before low tide when a current draining the mudflat concentrated the debris from a wide area into the shipping channel where it ran into the perpendicular channel current. This interaction caused a vortex which trapped the floating debris in very high densities. Both these samples show how plastic litter is very much affected by local current regimes, something to look into in the future.

Samples from the 2017 expeditions have been added to those from the 2016 Norway expedition, giving us more than forty samples from around the North Sea area. The next step will be to bring all this information together to create an overview of plastic densities throughout the North Sea. We will keep you posted as our analyses continue.

Reports by others

Marine Litter Vital Graphics

by: UNEP and GRID Arendal (Norway), 2016

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Wat spoelt er aan op het strand?

by: Stichting De Noordzee (the Netherlands), 2016

Download report