Lake Ainsworth Blue Green Algae Status

Red Alert as at 16 January 2020 

RED ALERT - LAKE AINSWORTH CLOSED [Update 4.20pm Thur 16 Jan]

Lab results are in on the blue green algae scum in the south eastern corner of the Lake, which have been found to be toxic.

Current advice is to avoid swimming at this time to avoid contact with slicks and scums present on the shore.

Warning signs will be erected advising people not to swim in the Lake, or touch slicks or scums that wash onto the shores. Users should always obey all signage erected by Council.

Council will increase the frequency of blue-green algae sampling and will continue to monitor the situation.

The aerator is currently switched on twelve hours a day (8am  to 6pm) from October to May.

If you would like to subscribe to Council’s weekly status update email list please email

  Red Level 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 Mode, local and health authorities should be contacted to assess risks to recreational users and appropriate measures should be taken to warn water users.
Water should not be used for primary recreation.

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

  Green Level occurs above 5000 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.
No restrictions on recreational use of the water.



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 Unit.

Enquiries: Development and Environmental Health Group, 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.

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.

What species affect Lake Ainsworth?

Species that have been identified from time to time in Lake Ainsworth include: dolichospermum, microcystis, pseudanabaena, chroococcus, lyngbya, and oscillatoria.

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, click on the WaterNSW  information.

Council follows the Guidelines for Managing Risk in Recreational Waters (National Health and Medical Research council NHMRC, 2008) 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

An aerator operates in the Lake 12 hours a day from October to April, generally overnight. This circulates the water to prevent the Lake stratifying, which is thought to help minimise algae blooms. 

New Lake Ainsworth Coastal Management Program (CMP)

Council currently has a project underway to develop a new CMP for Lake Ainsworth, which once finalised will replace the existing Lake Ainsworth Management Plan. The goal of the CMP is to provide the long-term strategy and management actions for this water-body and catchment area. It will be developed in consultation with relevant stakeholders and the community. Details and documents in relation to this program can be access at the project website.

Other Water Quality Information

Council also undertakes other monitoring at the Lake and information can be accessed here

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