Algal bloom monitoring
The Department of Water coordinate the monitoring of a number of popular recreational waterways in Western Australia for the presence of algae, including the Swan, Canning, Murray, Serpentine and Vasse Rivers.
When an algal bloom of human health concern is detected at potentially harmful levels the Environmental Health Directorate is informed, who will then advise the public not to have contact with the water.
Why monitor?
At low numbers algae cause no problems and are in fact part of the natural microscopic plankton of water. Occasionally the algae can grow very fast or "bloom" and accumulate into dense, visible patches near the surface of the water. Such blooms occur in slow moving, warm water that is high in nutrients such as phosphorus and nitrogen, and can be a serious public health and an environmental problem in many waterways throughout Western Australia, particularly in river and estuarine systems.
When are waters monitored?
Monitoring programs vary depending on the waterway. However, in general monitoring occurs from early spring through to late autumn when harmful algal blooms most commonly occur.
What is tested for?
Water samples are tested for species of phytoplankton. Phytoplankton is used to help determine the density of harmful algal bloom species in the water.
What are the results of sampling compared to?
The results of sampling are compared to the:
How do you find out if there is an algal bloom in the water?
The Local Government Environmental Health Officer should be able to advise you if there have been any harmful algal bloom warnings for a local waterway.
Health Warning signs are usually installed in prominent visible areas where people commonly access the water. Look for warning signs and follow the advice.
You can also check the Department of Health website for any recent press releases.
It is not possible to monitor every waterway in Western Australia for algae. This means you need to be on the look out for algal blooms before you go swimming in any waterway. Some “tell tale” signs which indicate that the water may be polluted with an algal bloom include:
- Brightly coloured water;
- Blue/green scums on the water surface;
- Brown discoloured water; and
- Oily films on the water surface.
If you notice any of these signs it is recommended that you do not go swimming.
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