Microscopic fragments of plastic are floating in the ocean, settling on seabeds, and washing up onshore 鈥� with unknown consequences for marine ecosystems, according to a new study.
Large plastic detritus such as bottles and packaging has well-known effects on sea life, strangling birds and fish and transporting alien species to new waters. And millimetre-sized plastic pellets 鈥� the building blocks of larger products 鈥� clog US harbours and soak up toxic chemicals from seawater, poisoning the creatures that swallow them (New 杏吧原创 print edition, 20 January 2001).
But little research has been done on microscopic plastics. So researchers led by Richard C Thompson, a marine ecologist at the University of Plymouth, UK set out to survey 鈥渢he tiniest bits鈥� they could find 鈥� specks of plastic about 20 microns wide.
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They scooped up sand from 20 sites around Great Britain, sampling sections of beach that are periodically exposed at low tide as well as sediment submerged beneath about 15 metres of water.
Rising tide
They added their samples to a salty solution and then separated what appeared to be manmade particles from those that floated to the top. Spectral analysis showed that about a third of these particles were synthetic polymers such as acrylic and polyester, and most were found in deep water.
鈥淲e can identify them as plastic but it鈥檚 impossible to tell where they come from,鈥� says Thompson. He suspects the source may be plastic packaging and pieces of net that are broken down by waves.
The team also discovered a rising tide of microplastics over the last 40 years. Merchant ships sailing along two routes in the North Sea have voluntarily trailed dustbin-sized filters behind them since the 1960s. The researchers picked out microplastics from the archived filters and showed the number of small plastic particles has tripled since the 1960s and 70s.
But their methods cannot identify particles smaller than 20 microns, and the filters were dragged 10 metres under water, not on the surface, where most flotsam drifts. The new data are therefore an 鈥渦nder-representation鈥� of what鈥檚 out there, says Thompson. 鈥淏ut I think the trends are more important.鈥�
Lugworms and barnacles
The microplastics may have consequences for marine life. When the researchers put the tiny shavings into tanks with three marine species 鈥� amphipods, lugworms, and barnacles, all of the animals ate the plastic.
鈥淲e really need to quantify the sources and sinks of this material and when we鈥檝e done that, we can look in more detail at the animals within those habitats to see if there鈥檚 any effects on them,鈥� Thompson told New 杏吧原创.
In the future, he will study whether the ingested plastic can poison the animals or block their guts.
But while the environmental effects are still unknown, Thompson says there is one crystal-clear message from the study: 鈥淲e should try to be more responsible with how we dispose of litter, and where possible, re-use and recycle plastics because they might last hundreds if not thousands of years.鈥�
Journal reference: Science (vol 304, p 838)