Cause of algae plague vague

Queensland’s Urban Utilities is investigating whether a once-broken stormwater pipe at The Lake Parklands has impacted Forest Lake’s water quality.
But rumours circulating across town suggest a sewage leak could be responsible for the lake’s recurring algae bloom, which cancelled the popular dragon boat races for a second consecutive year.
Other infrastructure around the lake, including a manhole and stormwater drains, is also being assessed to determine whether rainwater runoff, which can contain wastewater, is contaminating the lake water, according to Forest Lake councillor Charles Strunk.
In a statement, Cr Strunk said the broken stormwater pipe had not impacted local wildlife.
“This water is not affecting the wildlife of the lake; it is the blue-green algae and high nutrient loads coming into the lake from creeks, stormwater drains from residential properties, and animal faeces,” he said.
Cr Strunk asked Urban Utilities to brief him on the water quality of the lake and whether the surrounding infrastructure had affected the quality levels.
Data about current blue-green algae levels or blooms in Forest Lake is not publicly available.
In June last year, a large algae bloom, which persisted for months, forced the Hakka Multicultural Dragon Boat Festival to cancel dragon boat races in the lake.
This year, the festival was again unable to race dragon boats in the lake due to algae.
Hakka festival organiser Florence Day said she met with the council three weeks before the festival date, 1 June, where they told her it was too dangerous for people to have contact with the water.
It is unclear when the blooms will end. Ms Day said the council advised her that although they were working to improve the lake’s water quality, blue-green algae blooms were very difficult to clear up.
Blue-green algae, also known as cyanobacteria, thrives in warm, sunny, and still waters like Forest Lake, according to Water Quality Australia.
High levels of nutrients like nitrogen and phosphorus, nutrients that are also present in sewage, can also cause blue-green algae blooms.
Although the Lake Parklands is not directly connected to Oxley Creek, nearby waterway Blunder Creek collects water from the Lake before eventually flowing into Oxley Creek downstream.
Oxley Creek’s catchment also runs through the suburbs of Forest Lake, Inala, and Doolandella.
A water monitoring program run by the council tested 11 sites in the Brisbane LGA for levels of enterococci, a bacterium different from blue-green algae (and less severe in causing adverse health effects), caused by sewage leaks, storm water runoff, or faecal contamination, according to the council website.
Oxley Creek’s test site on Cliveden Avenue recorded consistently high levels of enterococci since the beginning of the year, peaking in April at a recorded 3300 colony-forming units per 100ml of water.
The council advises that recording of over 500CFU is likely to cause sickness in humans and wildlife if touched or ingested.
Enterococci are usually considered harmless, according to an Australian Government website, but high levels of the bacteria can indicate the presence of other, more harmful bacteria. Immunocompromised patients are particularly at risk of health effects connected to enterococci exposure.