Trawling the plastic ocean

4th April 2016

The oceans are full of plastic marine debris affecting water quality and sea life. It is an issue increasingly being addressed by and put on the agenda of environmental NGOs, research institutes and governments. Though, little is known about the scale of the problem and its consequences. Due to UV light plastics break down into small pieces that appear to be transported by ocean currents and concentrate in the ocean gyres. Far away from any Exclusive Economic Zone, no country has direct responsibility over cleaning up these gyres. It is a challenge which should ideally be taken up by the international community, since plastic marine debris and the health of our oceans, concerns us all.

In February 2013, the in Delft (The Netherlands) based organization, The Ocean Cleanup was founded to develop a technology to clean world’s oceans from plastics (http://www.theoceancleanup.com). Through two crowdfunding campaigns the organization channeled over 40.000 contributions totaling three million US dollars and created problem ownership. Soon after, they started experiments to test technologies’ feasibility. In 2015 two researchers of The Ocean Cleanup joined Masterskip from St. Martin to the Azores. Measurements were taken to research the vertical distribution of plastic marine debris in the Atlantic Ocean. Trainees were very welcoming towards bringing relevant research on board. Following its success, Masterskip and The Ocean Cleanup decided to continue the collaboration and also fish for plastics in 2016.

With the collaboration both The Ocean Cleanup and Masterskip hope to expand knowledge and increase environmental awareness on plastic marine litter. The Ocean Cleanup provided a special net, called a manta trawl. Samples are taken, put in the freezer and will be brought to the laboratory in Delft to calculate ocean plastic concentrations. Since leaving St. Martin we have been using the manta trawl four times. The first time anchored in a bay at the British Virgin Islands to test how to deploy the net from the ship and how to take it back on board in particular. After the successful test we fished for plastic marine debris three times.

Soon we realized fishing for plastics is a challenge. The Wylde Swan is a fast sailing vessel, so when there is wind the speed exceeds 5 knots. Below 4.5 knots the engine is turned on to maintain a comfortable speed. Ideal speed to tow the manta trawl is 3 – 3.5 knots, which is lower. Towing with a speed of more than 5 knots might have influenced the amount of plastic found in the cod-end. Suitable weather conditions for fishing occurred at the moment we were close to the Atlantic gyre. A day later the wind force as well as the wave height increased, making it impossible to plan more tows. The Atlantic gyre is from west to east somewhat egg shaped and located between 25?N-60?W and 35?N-30?W with its center at 29?N-54?W. Even though all three tows were just outside the gyre and the speed exceeded the ideal speed, we did find plastics in the cod-ends.

On lazy Monday, our day off, we made our own trawl made out of trash to be used by a speed exceeding 5 knots. We attached a sleeve of an old t-shirt to two cans, in one we made holes to tie it to a rope and we attached the cod-end with a water hose clip to the other can. Although the diameter of the can limited the volume of water going through the self-made trawl, we did find plastics in the cod-end! The ocean might look like a deep blue empty surface, but these experiments have shown the Atlantic Ocean contains micro plastics. After the Azores we will hopefully be able to do additional measurements outside the Atlantic gyre and use our previously taken samples to calculate ocean plastic concentration (in pieces per km2).

By Jan Joris Midavaine

Fishing for micro plastics with Masterskip Wylde Swan

Fishing for micro plastics with Masterskip Wylde Swan