Ellen Phiddian
Cosmos science journalist
Adelaide’s freshwater streams are loaded with microplastics, according to a study by Flinders University.
These tiny plastics, less than a few millimetres in size, are showing up everywhere – but the total scope of their environmental damage isn’t yet clear.
It’s thought that, besides building up in marine and terrestrial life, microplastics could carry diseases and release damaging substances into the environment.
The survey of eight waterways found that 72% of microplastics flowing into Gulf St Vincent are textile fibres, while 17% come from fragments and 8% come from cosmetic beads: tiny plastics used in cosmetic products.
The study, which is published in Science of the Total Environment, found an average of 6.4 microplastic particles per litre of water, although numbers varied considerably.
This is higher than reported values in some European streams – but the researchers point out that different ways of collecting and counting microplastics could explain the higher results.
“Until everybody’s sampling everything in the same way, it’s very hard to compare,” says lead author Professor Sophie Leterme, from Flinders University’s Institute for Nanoscale Science and Technology.
Leterme and colleagues analysed water collected by automatic sampling stations on eight Adelaide streams: Magazine Wetland, Torrens River, Brownhill Creek, Sturt River, Field River, Christie Creek, Onkaparinga River and Pedler Creek.
“Every time five to 10 megalitres flows down the river, we have a half a litre of surface water that is sampled,” says Leterme.
The water is collected in a drum, which is sampled every four weeks – unless the stream levels are too low to collect enough water, which occasionally happens over summer and autumn. In total, the researchers looked at 34 samples collected between mid-2020 and mid-2021.
They passed the samples through a series of filters, to pick out particles between 20 micrometres and 5 millimetres in size.
Then, particularly in the case of textile fibres, the researchers had to confirm the particles they’d found were microplastics.
“The problem is to identify if those fibres are synthetic, or if they’re natural – because a lot of plants have fibres,” says Leterme.
This required microscope analysis, and Raman spectroscopy: a technique that can identify the chemical structure of substances by shining light through them.
“It is really tedious work,” says Leterme.
Read more: Ocean microplastics captured using sound
All streams had microplastics in them, even though five of the sampling sites were within a kilometre of waste management facilities.
The microplastics ranged in abundance from 1.2 particles per litre at the least polluted spot, to 30 particles per litre in the most polluted.
Each site recorded a majority of microplastics as textile fibres, which the researchers suggest can often come from wearing and use of clothes and textiles.
“This study provides a baseline understanding of the microplastic load entering the Gulf St Vincent, and hopefully this will be a beneficial step in the process to understand the impacts microplastics are having in the marine waters of our state,” says co-author Elise Tuuri, from the Plankton and Marine Microbiology Lab at Flinders.