An invasive aquatic weed that can affect river health and biodiversity has been found in a Perth waterway.
The Amazon frogbit was first spotted in Bayswater Brook late last month.
Originating from Central and South America, the weed spreads rapidly via fragments from the parent plant, which can produce multiple seed pods, each containing up to 30 seeds that are viable for at least three years.
It is used in WA for aquariums, but when disposed of incorrectly it can congest drains, waterways and wetlands, displacing native vegetation and affecting water quality.
Department of Biodiversity, Conservation and Attractions drainage manager Kate Bushby said work was being done to remove the weed and search for the source along drainage lines.
She warned the weed may have found its way downstream and possibly upstream with tidal movement.
"Booms have been put in place to prevent further movement of the weed down the brook," she said.
"We have installed a barrier around the outlet of the basin in Browns Lake Reserve to contain what is currently believed to be the main source of frogbit into Bayswater Brook."
There have been several infestations of the weed recorded in Perth's east and south since 2013, but they were all isolated incidents.