Citizen researchers are helping to count the fragments of polystyrene that pollute the river

Finally, it is ingested by fish, birds and all kinds of aquatic animals that fill their stomachs and often suffocate their lives.

Imported polystyrene is particularly dangerous and contains chemicals that escape Australian regulations, according to Despotellis.

No one is quite sure how much polystyrene flows down the Yarra, but it is estimated to be by far the largest source of waste in the river.

Mr Despotellis, project manager for waste at the Yarra Riverkeeper Association, aims to help figure it out with the help of a small and growing army of enthusiastic volunteers.

His wanderings up the river give him large amounts of polystyrene that are entangled in river debris.

The clutter is split and sealed in Ziploc bags and sent out to a growing number of volunteers who – trapped at home during Melbourne’s months of lockdowns – are happy to sort it out and count the number of polystyrene fragments.

Polystyrene is the path of the river keepers.

Polystyrene is the path of the river keepers.Credit:Jason South

“There can be hundreds or thousands of pieces in a single sample,” says Despotellis.

The size of each piece determines whether it will be counted as micro-plastic (less than five millimeters) or macro-plastic (greater than five millimeters). Previous studies have already identified macroplastic polystyrene as Yarra’s biggest single polluter.


As Riverkeeper’s voluntary citizen-science review progresses, a more accurate estimate of the size of the problem will emerge, equipping the Riverkeeper organization with the firepower to lobby government and industry to increase efforts to tackle the problem.

“If we can say, for example, that there are 2 billion pieces of polystyrene that pollute Yarra, people will take it more seriously,” Despotellis says.

Riverkeeper is conducting an associated investigation to determine the main sources of the fly-away styrofoam.

Once a number of major offenders are identified, such as poorly controlled loading docks at major retail centers, construction sites or industrial areas, Despotellis says additional pressure could be exerted.

Meanwhile, civilian researchers in closed homes in Melbourne are busy counting the ways in which a city compromises the health of the river.

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