Algae Alert


Why do we need Algal Alerts?

To try to ensure the health and safety of water users and their stock in the Murray catchment, DLWC continually monitors rivers, creeks, lakes and other public waterways for the presence of blue-green algae. If blue-green algae numbers increase above certain levels, MRACC issues ALGAL ALERTS via the media (radio, television, newspapers and this web site). Water users can then take appropriate action to avoid the problems associated with a blue-green algal bloom.

Blue-green algae (BGA) are photosynthetic bacteria which occur naturally in our waterways. When certain species are present in high concentrations they can become harmful to the health of humans and animals, as well as causing the water to taste and/or smell bad. Although to date no Australian’s death has been directly attributed to blue-green algae, significant stock losses have been caused by toxic blue-green algae.

What are Algal Alerts?

ALGAL ALERTS are public warnings issued by MRACC based on their evaluation of the RISK from blue-green algal to users of public waters. Alerts are based on:

  • Identification of algal species (and hense, potential toxicity of the bloom),
  • Determination of the concentration (numbers and size) of algal cells in the water,
  • Consideration of the area, volume and location of affected water in relation to potential water users, and
  • Other factors such as where water is flowing and mixing, the wind direction and speed, weather forcasts, the season and history of blooms at the site.

What are Algal Alert Levels?

Note: BGA (blue-green algae) ALERT LEVELS are a guide to the state of a bloom. They are based on water samples which may not represent the full picture. Conditions change from day to day and over short distances in a waterway. Treat the alert levels more like a weather report with a fire or graziers warning than a doctor’s diagnosis.

Alert LevelWhat this meansWhat you must do
HIGH ALERT” Bloom ” conditions apply. Water may have a green tinge and musty or earthy odour.In calm water scums may form on the surface and be blown towards the shoreline. In windy conditions algae may be mixed into the water column and be less visible.Usually more than 15,000 cells/mL of BGA present. Algae may be toxic to humans and animals.Do not drink untreated or boiled water from the contaminated area.Seek an alternative water supply.Avoid contact with, or use of the water.Do not fish in areas where algal scums are present.Do not eat mussels, crayfish or shrimp.Dogs and stock are at particular risk, keep them away from affected areas and provide an alternative water supply.
MEDIUM ALERTMusty or earthy smells common. Blue-green algae visible as green flecks in a bucket or glass jar.Water contains 2,000 to 15,000 cells/mL. There are enough blue-green algae present for a population explosion.Water, temperature and movement conditions suitable for algal growth and if they remain this way a HIGH ALERT may result in a few days.Use alternative drinking water supply for humans and animals or treat water with activated carbon.Carefully clean fish removing all gut material.Do not eat yabbies, mussels or shellfish.Avoid scum when collecting water for any purpose. Keep stock away from leeward shoreline of affected water body.If you are sensitive to algae avoid direct skin contact with the water.Pets may be sensitive to algal toxins.Report BGA in public waterways to DLWC or local council.
LOW ALERTBlue-green algae not present at bloom levels. However, numbers are sufficient (500 to 2,000 cells/mL) and environmental conditions sufficiently favourable for rapid algal growth.Some species of algae can cause taste and odour problems at low cell concentrations.Bright green flecks (algal clumps) in a bucket or jar of affected water mean there is a strong case for a MEDIUM ALERT.Use an alternative water supply if available and prepare for a medium alert in weeks.If humans or stock drink the affected water, watch for signs of illness (nausea, gastroenteritis).It may be possible to chemically treat farm dams to prevent further bloom in the short term. Get expert advice to avoid risking future blooms.