TENS of thousands of individual microplastic items are washing into Dee Why Lagoon, with researchers concerned about the impact on marine life and humans.
An eight-month study in Cromer, which is part of the lagoon's catchment, has prevented 76,000 items (10 kilograms) of synthetic debris and litter from washing into the waterway.
Metal mesh traps were placed at the stormwater intakes off streets in the suburb and Australian Microplastic Assessment Project (AUSMAP) research director Dr Scott Wilson said the Cromer catchment was chosen for a number of reasons.
"It had a bit of industry, a bit of residential, there's a school, there's playing fields, it was a good example," he said.
While researchers expected litter to be trapped, Dr Wilson said they did not expect so many microplastics at this early stage of the process. "The previous held belief was that the wrappers washed down the drain, down into creeks and then broke up when they were in the ocean or the lagoon," he said.
The traps were in place from June 2020 to February 2021, and of the 76,000 items of synthetic debris and litter that was caught, more than 63,000 pieces were microplastics, with around 50 per cent of that being plastics and rubber. The average length of microplastics in the study was 2.5mm long.
AUSMAP said if the data for the 14 drains were extrapolated across the entire Dee Why Lagoon catchment (268 ha), it estimates that more than 650,000 (550,000 as micro) litter items would flow into the lagoon monthly.
"The lagoon is an important wetland for migratory birds and important breeding ground for marine life and being one of the last natural lagoons in the Sydney region we thought it was important to find out a bit more about where this microplastic is coming from," Dr Wilson said.
He said microplastics are easily eaten by marine life and international studies have shown plastic can affect the animal.
"It could affect growth, it could affect development, it can actually kill the animal. There's a whole range of chemicals associated with these plastics that can also cause harm," he said.
Microplastics also have the potential to impact human health, Dr Wilson said.
"We know some of the chemicals [in microplastics] are probably more insidious in terms of their impacts because you only need a little bit of this chemical to cause a toxic effect in the body," he said.
The research was funded through a NSW EPA litter grant and Dr Wilson it hopeful it will help inform decision making on a local and state government level.
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