Anna Cummins and Marcus Eriksen from 5 Gyres deploying the manta trawl. Photo credit: Paula Alvarado
It's our fifth day on the Sea Dragon, the sailboat that's taking a crew of 13 people on an expedition with the 5 Gyres project to find out if the South Pacific presents the same plastic pollution found in the North Pacific, North Atlantic, Indian Ocean and South Atlantic.
With clouds finally opening up to let the sun charge our internal batteries, today was the much anticipated day we started trawling: Collecting floating material from the surface of the ocean with a special device designed by the 5 Gyres team.
The trawl in the water in the middle of the South Pacific. Photo credit: Paula Alvarado
The device we used today was the manta trawl, specifically designed to capture floating material measuring the amount of water that it's covering. It's composed by a metal structure that keeps it afloat, a flat and cylindrical net that sink so that air doesn't go through them, and a flow meter to measure the cubic meters that go through it.
Deployed every 60 miles, the trawl is towed for one hour. When taken out, the materials found inside of the mesh are placed in a recipient and conserved in formaldehyde.
The samples are afterwards sent to the Algalita Foundation, which analyzes each sample and classifies all the materials found in them, separating plastics by size, type (lines, film, fragments, foams, pellets) and color.
By running that data with the amount of water trawled (measured by the flow meter), they can get an idea of the density of plastic in the gyres (amount of plastic per unit volume).
When the manta is not working, there's a high speed trawl in the water that takes samples but that doesn't measure the amount of water, so it can only offer data in regard to area. With the same analysis described before, it can give a sense of the surface abundance of plastic in the gyres (amount per unit area).
A first sample of the South Pacific waters. Photo credit: Paula Alvarado
Some of these samples are also shared with scientists who are studying different aspects of plastic pollution in the oceans, like the presence of persistent organic pollutants. Additionally, some samples are kept for educational purposes such as exhibitions (some of the jars are being exhibited now at six museums around the Mississippi river in the US).
Although the results from the lab on all the samples are not complete, the North Pacific gyre appears to be the most dense in plastic accumulation. However, the ocean dynamics in the South Pacific make this gyre the one with the tightest accumulation zone, so that could change.
The first sample taken from the sea, shown above, didn't show presence of plastics to the naked eye, which doesn't mean that there wasn't any but that at least it wasn't obvious. We're still very far from the epicenter of the gyre, so that could change in the next trawls.
Meanwhile, the crew has been enjoying a little bit of sun and music on board while we prepare for the hard work that lies ahead.
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