Microplastic threat to Sydney Harbour

The first survey of the presence of tiny fragments of plastic in the sediments has revealed concerning results that warrant more research to determine the severity of the problem.

The research was led by Professor Emma Johnston, who is Director of the Sydney Harbour Research Program and a marine ecologist in the UNSW School of Biological, Earth and Environmental Sciences.

Microplastics are tiny fragments or threads of plastic less than 5mm in length. They come from items such as clothing fibres and facial scrubs, or larger pieces of plastic that break down once they enter the Harbour.
The tiny microplastics absorb pollutants and are then ingested by marine life, transferring the contaminants throughout the food web.
Although plastics degrade with time, the exact time scale is unknown, with some studies suggesting it could range from 50 years to hundreds of years.
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Professor Johnston and her team from the Sydney Institute of Marine Science (SIMS) are alarmed by their initial results.

"Microplastics were found in sediments throughout Sydney Harbour and we observed animals ingesting them. This is the first information we have and it certainly warrants further research," she says.

"Microplastics are an emerging threat that requires attention. The most globally abundant contaminants are plastics of which more than 280 million tonnes are produced each year.

"Plastics enter and persist in environments from the poles to the equator and down to the depths of the sea.

"Although larger pieces of plastic can be removed by sewage treatment plants and stormwater filters, no existing filtration methods retain microplastics, so they continue to be released.

"This is concerning because laboratory trials overseas indicate this material is likely to be present in animal tissues and food webs. The lack of information is hindering management of the problem in busy harbours such as Sydney.

"Risk analysis cannot yet be applied to microplastics because we lack fundamental information about levels of contamination in habitats and the uptake or consequences of this material in natural systems such as the harbour," Professor Johnston said.