Fishing for plastic in the Southern Ocean

The Guardian reports, 10th December 2013: ” Erik van Sebille is looking for something very much out of the ordinary in the Southern Ocean: plastic. He has come to one of the most remote parts of the world — as far as it is possible to go from major concentrations of people — to look for the stuff humans throw away.

Researcher Erik van Sebille drags a net from the stern of the Akademik Shokalskiy to collect seawater samples. His research involves monitoring the concentration of plastic particles.
Photograph: Laurence Topham/Guardian

Van Sebille, an oceanographer at the University of New South Wales and one of the research leaders on the Australasian Antarctic Expedition, was one of the first to start his scientific work aboard the Shokalskiy. In the morning on our first full day at sea, he threw a two-metre-long planktonplankton Plankton is a generic term for a wide variety of the smallest yet most important organisms form that drift in our oceans. They can exist in larger forms of more than 20cm as the larval forms of jellyfish, squid, starfish, sea urchins, etc. and can be algae, bacterial or even viral down to as small as 0.2µm. They are nutrient and light dependent, and form the essential foodchain baseline for larger dependent aquatic lifeforms. Fish species rely on the density and distribution of zooplankton to coincide with first-feeding larvae for good survival of their larvae, which can otherwise starve. Man-made impacts such as dredging, dams on rivers, waste dumping, etc can severely affect zooplankton density and distribution, which can in turn strongly affect larval survival and thus breeding success and stock strength of fish species and the entire ecosystem. They also form the essential basis of CO2 take up in our seas ecosystem, hence Global Warming. net, with a pint-sized jar attached to one end, overboard. After five minutes dragging the assembly behind the ship, he fished out the jar and held in his hands something that looked a bit like pea soup — seawater filled with plankton, krill and, perhaps, bits of plastic. For his research, he will take many more seawater samples at different latitudes, sieving each one to identify the constituent parts.

The plastic he is looking for is the stuff that starts off as consumer goods and ends up in the sea as waste. The plastic is broken down over time, by sunlight, into fragments no more than a millimetre across. These particles can float for hundreds to thousands of years on the surface of the sea. Scientists have identified huge areas of the North Atlantic and Pacific oceans, for example, where the water currents force the plastic particles to accumulate. In some of these places, there seems to be more plastic than plankton on the surface. The particles can attract algae, absorb toxic chemicals and have major impacts on the entire marine food chain.

So far no one has carried out measurements of plastic in the Southern Ocean, partly because it is so remote but also because oceanographers have assumed that the prevailing surface currents would limit any plastic build-up there. Van Sebille is aiming to fill that knowledge gap. “We want to find out, in a systematic way, how much plastic there is,” he tells me. “Especially if, as we go from relatively close to New Zealand and further south, how quickly the amount of plastic actually decreases.”

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