Algae bloom prompts warning

Kate FieldingSouth Western Times
Residents have been warned not to contact the water at Horseshoe Lake in Bunbury.
Camera IconResidents have been warned not to contact the water at Horseshoe Lake in Bunbury. Credit: Graphic / South Western Times

An algae bloom is covering a Bunbury lake, prompting a warning for residents to avoid direct contact with its water.

Department of Water and Environment Regulation has analysed Horseshoe Lake in East Bunbury, finding three species of harmless macro algae and low densities of blue-green algae which are considered to be of “low concern” at the moment.

Bunbury City Council has erected standard health warning signs around the wetland and says it will continue to monitor the bloom over the coming weeks.

The council has advised that algae is a natural part of the wetland system but big blooms can occur with the onset of warmer weather when water in the wetland becomes too rich in plant nutrients.

This includes phosphorous and nitrogen, much of which can be attributed to use of garden and lawn fertilisers at this time of year.

Locally applied fertilisers enter the wetlands through stormwater pipes or leaching into the ground water, prompting the council to urge residence to reduce use of fertilisers.

The council says residents can help in keeping the city’s waterways healthy by following a number of recommendations:

• Only apply fertiliser, if required.

• Apply fertiliser in accordance with directions during spring or early autumn, when plants are actively growing.

• Do not over-water as this washes fertilisers into water ways.

• Improve the soil with organic matter and other additives to improve nutrient retention.

• Grow native or water wise plants which require less fertiliser and water.

• Use water and fertiliser efficient grasses such as Buffalo and Zoysia.

• Reduce the areas of lawn.

The council says it minimises its use of fertilisers, where possible, focussing its responsible use on high amenity lawn areas and sports fields as required.

Is is also replacing some grassed areas with native and water wise plants and mulch and a number of water sensitive design features have been installed along roadsides to help reduce pollution and nutrients running of roads into wetlands, according to the council.

More information on how to use fertiliser responsibly is available here and here.

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