An algal survey has identified a mix of Lyngbya sp – a cyanobacteria commonly known as blue-green algae – and the free-floating macro-algae species Ulva and Rhizoclonium, which are visible as a large algal bloom in waters east, and the channel north, of Molloy Island.
DWER Water Science Branch Manager Malcolm Robb said water quality and algal samples taken by DWER on 13 December 2018 had been sent to the Phytoplankton Ecology Unit laboratory in Perth to determine the particular species of Lyngbya.
Mr Robb said that with more than 20 species of Lyngbya, toxicity levels depended on both the particular strain as well as environmental triggers
“Lyngbya is potentially toxic but the macro-algae are not toxic,” he said.
“DNA analysis of the samples will accurately determine the Lyngbya species and whether it can produce toxins. Water quality monitoring conducted on-site has shown dissolved oxygen concentrations are within the acceptable range.”
Mr Robb said people in Augusta could expect to see non-toxic macro-algal accumulations along shorelines.
“DWER will continue to monitor the area during this high-risk period and implement a response plan as required,” he said.
Lyngbya grows on the bottom of a range of shallow waterways, where it forms dark greenblack mats. Under certain conditions, Lyngbya can float to the surface and decompose under sunlight, becoming pungent and accumulating on beaches.
Mr Robb said the reappearance of Lynbya and the extensive free-floating green macro-algal blooms followed this year’s late-winter rains and run-off into the estuary, which is open to the ocean at the mouth.
The Department of Health (DoH) has advised people to avoid swimming, wading, kayaking, water-skiing, jet-skiing, fishing, crabbing or collecting shellfish between Molloy Caravan Park and the ferry crossing, or in waters around Molloy Island where the algal bloom is visible. Pets and livestock should also be kept away from the water during the bloom.
People should report algal blooms to DWER’s ALGALWATCH during office hours on 6250 8064, or the relevant local government authority. More information on algal blooms is available on DWER’s website at https://www.water.wa.gov.au/water-topics/waterways/threats-to-our-waterways/algal-blooms.
