Lake Ainsworth Blue Green Algae Status

Alert Definitions

Green Level Amber Alert Red Alert

Green Level occurs above 500 cells/mL of Microcystis aeruginosa or >0.04 mm3/L of total cyanobacterial biovolume but below the Amber alert level. At this level routine sampling for algae should be undertaken.

Amber Alert Mode is triggered when Microcystis aeruginosa concentrations are between 5000 and 50,000 cells/mL or the biovolume of all cyanobacteria is between 0.4 and 4mm3/L. At this alert level investigations into the causes and increased sampling of algae should be undertaken.

A Red Alert Action Mode is in place when >50,000 cells of Microcystis aeruginosa are present or a biovolume of all toxin producing cyanobacteria exceeds 4 mm3/L or if the total of all cyanobacteria (toxic and non toxic) exceeds 10 mm3/L or scums are present for long periods. At Red Alert mode, local and health authorities should be contacted to assess risks to recreational users and appropriate measures should be taken to warn water users.

No restrictions on recreational use of the water.

Council will continue to monitor weekly, however care should be taken to avoid any slicks or scums should they develop.

Water should NOT be used for primary recreation.

Lake users should note any signage at the site and should report any sign of algae which may appear like a green paint spill on the surface of the water to Ballina Shire Council's Environmental Health division.

Enquiries: Planning and Environmental Health Division, Ph 02 6686 1210.

Algal Information Line: 1800 999 457

To report algal blooms after hours 02 6626 6954

What are blue green algae?

Blue green algae are single celled organisms of ancient origin. Otherwise known as cyanobacteria there are about 40 species known in this country. A selected number of these exhibit toxic properties from time to time. Species that have been identified from time to time in Lake Ainsworth include: dolichospermum, microcystis, pseudanabaena, chroococcus, lyngbya, and oscillatoria.

The algae may sometimes (but not always) be seen as a bluish green scum on the surface of the water or the shoreline when the water is calm.

How can blue green algae affect me?

Skin and eye irritation is a common reaction. At stronger concentrations nerve and liver toxins may be present. Some people are more likely than others to suffer as a result of contact with blue green algae. Anyone who is aware that they are acutely allergic to blue green algae should avoid contact with the waters of Lake Ainsworth. To learn more about this organism, how it forms, and what it can do to you, visit the WaterNSW website.

Council follows the Guidelines for Managing Risk in Recreational Waters (National Health and Medical Research council NHMRC, 2008) (1.21mb pdf) for recreational water when determining whether health warnings are necessary.

Warning signs are erected:

  • when blue green algae concentrations exceed the NHMRC guidelines, and/or
  • when concentrated algal slicks and/or scums appear.

The signs are removed:

  • when two consecutive weekly samples of blue-green algal concentrations fall below the NHMRC guideline levels, and slicks and/or scums are no longer present.

Sampling is undertaken by Council’s environmental health officers in accordance with NHMRC guidelines and are analysed by a NATA accredited laboratory. Results are generally available within 24 hours. Testing is generally carried out weekly between October and April and sampling may be increased to several times a week when algae blooms appear imminent or are in progress.

Lake Ainsworth Aerator

Council is operating the aerator 24 hours a day from October to May 2023/2024. The aerator circulates the water to prevent the Lake stratifying, which is thought to help minimise algae blooms. 


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The General Manager
Ballina Shire Council
PO Box 450
Ballina NSW 2478

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Ballina NSW 2478


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