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Plastic bags in the sea biofilms and buoyancy

Wednesday 1st December 2010

Scientists at the Marine Biological Association have shown that the properties of plastic debris in the sea change once it is covered by a biofilm of microbes.

The research suggests that microbes make plastic less buoyant and will help us understand what happens to plastic debris in the sea - vital knowledge if we are to deal with what has become an international marine pollution problem.

One of the reasons plastics are so useful is that they are waterproof and actually repel water. As demonstrated in the research, the biofilms which develop on plastic debris in seawater reduce this water repelling property and the plastic becomes less buoyant.

Large plastic debris can entangle marine animals or be problematic if it is eaten by them. Plastic tends to break down in the marine environment into tiny pieces that become available to all sorts of animals - such as mussels, shrimps and small fish - that feed on plankton or other organic particles. The changes in buoyancy behaviour caused by biofilms mean that plastic debris may be a hazard to different organisms as it sinks in mid water or to the seafloor.

The experiment looked at colonisation of polyethylene plastics which takes place in the first few weeks 'at sea'. Researchers found no evidence in these early biofilms of bacteria that degrade plastics.

The reference for the paper is:

Delphine Lobelle & Michael Cunliffe (2011) Early microbial biofilm formation on marine plastic debris. Marine Pollution Bulletin doi: 10.1016/j.marpolbul.2010.10.013.

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