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Research shows how micro-plastics move around the deep seas

Editorial Staff

Research by the UK's National Oceonography Centre (NOC) and the University of Manchester forms part of a broad international collaboration. It reveals that micro-plastics often accumulate on the deep sea floor in the same place as diverse and dense marine life communities. That's no big surprise. But how it gets there is.

The research shows that the same submarine sediment flows that transfer the oxygen and nutrients needed to sustain life also transport micro-plastics from urban rivers to the deep-sea floor via pathways such as submarine canyons.

An illustration at https://noc.ac.uk/files/images..., drawn by the two authors of the paper, shows the probable sources, pathways and accumulation points for micro-plastics in the ocean.

Dr Ian Kane of the University of Manchester is the lead author on the paper. He said "Micro-plastics have been found in nearly all environments on our planet yet we only have a very limited idea of how they are transported; particularly in the deep sea. " Co-author, Dr Michael Clare of the National Oceanography Centre at the University of Southampton, said "only a small amount - about 1% - of the plastic in the ocean floats on the surface. Most of the rest sinks. Ocean currents and other near-seafloor flows appear to control where the sinking plastic ends up."

The full paper, published at Frontiers in Earth Science, is called "Dispersion, Accumulation, and the Ultimate Fate of Micro-plastics in Deep-Marine Environments: A Review and Future Directions."

The authors say that since plastics became part of ordinary life, an estimated 8,300 million tons of non-biodegradable plastic has been produced. Much of that has not been recycled and has ended up in the natural environment where, over time, significant proportions have broken down into micro-plastics.

Often, the focus on plastics in the oceans is on floating shampoo bottles or the tens of millions of drinking water bottles discarded every day, on the rubber duck flotilla or the plastic islands drifting in ocean currents. But those are the big bits and in recent years attention has begun to focus on what happens when they break down: they don't dissolve and they don't disappear - they become ever-smaller granules. What is worrying scientists is that those granules have found their way into the food chain via even deep sea fish - worse, they cannot be simply picked out and thrown away with the fish-guts: some are so tiny that they pass into the flesh of the meat we eat. In addition to granules, there are micro-fibres, many from synthetic clothing much of which, ironically, is produced from recycled plastics.

The research into micro-plastics in the ocean is therefore important. It is known that vast amounts of plastics are dumped into the seas. The new research shows something even more worrying: micro-plastics that are generated in rivers and, possibly, even landfill, have a far greater range of travel than previously imagined and, ironically, it's nature that's providing the means of transport.

Further Reading: https://www.frontiersin.org/ar... (free to download and read)