Floating sensors predict where plastic will wash up on Galapagos beaches

Oceanographers Erik van Sebille and Stefanie Ympa from Utrecht University are developing a predictive app that lets the Galapagos National Park remove plastic from beaches as it washes up.

Several floating sensors, also known as ‘drifters’, have been thrown overboard at key points around the Galapagos Marine Reserve. Every 10 minutes, the drifters save their GPS location, and update the researchers about their journey via a satellite every 4 hours. Tracking how the drifters move around the islands will improve the oceanographic models of the area, combining ocean current data with wind, tide and wave models. They will then be able to predict where future plastic will wash up, and focus clean-up efforts in those areas.

However, it’s not just a simple matter of going where the plastic is washing up.

“Many factors come into play when we want to give good advice to park rangers on picking up plastic: not only ocean currents, but also accessibility of coastal areas and impact on local flora and fauna.” – Stefanie Ypma, Institute for Marine and Atmospheric research Utrecht (IMAU)

Galapagos is home to some spectacular and diverse coastlines, form jagged cliffs, to soft sand and mangroves, leaving some of these areas really hard to reach. By using a predictive app, areas that are very vulnerable to plastics could be prioritised and cleaned up quickly, whereas areas where regular human presence would disturb the local animals will be carefully managed.

The journey from Utrecht University to Galapagos was not a smooth one for the drifters, as Erik and Stefanie were not able to travel to Galapagos to release the drifters due to the COVID-19 pandemic. So, after a bit of a delay, 50 of the little floating sensors travelled unaccompanied to the islands. They ended up with Dr Inti Keith at the Charles Darwin Foundation, who is charged with taking them out to specific points and throwing them into the ocean.

© Rashid Cruz and CDF.

Some of the drifters are now floating around the Galapagos archipelago. What makes these drifters special, is that they are very small, lightweight and float at the ocean surface. “The more they look like ‘real’ ocean plastic, the better it is for our model” – Stefanie Ypma.

Up until now, drifters deployed around Galapagos have floated at a depth of around 15 metres. This is an ideal depth to map temperatures and nutrients, but not so useful for mapping plastics which often float and are affected by waves and wind.

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