Since December, Professor Patricia Holm from the Department of Environmental Sciences has been on board the research vessel Polarstern. Though there is only limited internet communication, we managed to get in touch with her to learn more about her expedition to one of the most remote places on earth, the Weddell Sea. Professor Holm’s goal is to investigate the extent of plastic pollution in this region. In the following, she shares her activities during a smooth day on board the Polarstern.
“After six weeks at sea, it feels strange to wake up without feeling the vessel swinging. Still lying in bed, I have a hunch: no waves, no ice-breaking, smooth sea — in other words, the best conditions for our expedition. I am on board the research vessel Polarstern, a German icebreaker.
We left Cape Town in mid-December to steam towards Antarctica, specifically the Weddell Sea, one of the most remote ocean regions. We are here to search for microplastics, i.e. tiny particles of plastic that are smaller than 5 millimeters. For a long time, Antarctica has been thought of as a highly isolated, pristine ecosystem. More recently, however, it has become clear that even this remote region is no longer protected from the increasing levels of plastic waste that have been found in the world’s oceans. The goal of this expedition is to study the Weddell Sea, to record the levels of microplastic contamination out here, and, if significant, to find out where these particles might be originating from.
Much station work is planned for today. Altogether, there are approximately 50 scientists on board, focusing on research activities in the fields of biology, geology, geophysics, glaciology, chemistry, oceanography, and meteorology. Our time slot is 10:09 am, as announced on the ship’s intranet. Our goal is to filter as much water as possible. We use a specialized net to gather water samples. It`s called a Manta trawl with a mesh size of 300 micrometers. It has two wings, allowing it to surf on the water and to filter the water as it moves with the ship; half an hour of trawling results in a filtered volume of about 200,000 liters of water.
Before breakfast, I visit the bridge to see whether we are on schedule. I also check with the nautical officer regarding the recommended velocity of 2 knots and wind direction during deployment and trawling. All this is important to get a water sample that is as little affected by the ship’s activity as possible and to avoid damage to our sampling device.
It’s time to prepare our Manta trawl. Together with my research team, I carry the light device on deck; it’s still covered with cotton blankets to avoid contamination from the varied activities on board.
The experienced and helpful crew is ready to go. We fix the net to the winch and lower it into the water. It’s always a breath-taking moment: can we deploy the net in the right position, the mouth directed straight towards the bow of the vessel?
The next few minutes will show whether our net will also collect a lot of algae. This would make our analysis difficult, because we would first have to separate the sticky algae from presumptive microplastics particles. But not this time — an almost clear cod end indicates that there is barely any biological activity going on at the surface of the water in this location.
Later on, our analysis of the water samples shows relatively few microplastic fragments. Over the course of 20 Manta trawls, we found an average of eight particles per 200,000 liters of water. This is a tiny fraction of what has been found in other parts of the ocean. That said, there can be no doubt that even this remote region is not immune to plastic pollution. Our colleagues, who observe birds and marine mammals, have more than once observed plastic garbage drifting on the sea.
The big question is: where is this plastic coming from? Is it a result of increasing tourism, fishing or research activities? Or could it get here across the Antarctic Circumpolar Current, which flows clockwise around the continent and was historically thought to be impenetrable? To further investigate the matter, we will be taking water and ice samples to our cooperation partner on Helgoland for more in-depth analysis.
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