Blue Green Algae

Freshwater blue-green algal blooms can be recognised by a discolouration of the water, by scum on the water surface, or by an earthy or musty odour coming from the water. (Water NSW, 2021)

Blue-green algae thrives in the warm surface layer of a water body that forms, usually, from spring through to autumn throughout Australia's inland waters. Blue-green algae possess gas pockets which prevent them from sinking so that they remain in the surface layer and can access the abundant light near the water surface, leading to rapid growth.

Signs of a blue-green algal bloom.

However, algae that are toxic can only be positively identified by an expert. If you think there may be a blue-green algal bloom in a water body, you should contact either the local council or the management authority for the water body, or your local RACC.

Toxic algae can only be identified by an expert.

Always act as if a waterway is polluted until confirmed otherwise.

All Bellingen Riverwatch citizen scientists must wear waterproof gloves at all times when doing water testing.

How to report algal blooms.

The algal information line on 1800 999 457 provides recorded information on algal alerts.

To report suspected algal blooms during business hours, phone Dane Clarke, Algal Coordinator, Coastal (Metropolitan and South Coast, Hunter and North Coast) on (02) 9865 2559 (Parramatta).

To report suspected algal blooms at all other times, an email can be sent to RACC@waternsw.com.au with details and any available photos of the suspected bloom. A WaterNSW RACC coordinator will respond to your inquiry at the earliest opportunity.

If blue-green algae multiply to high numbers, toxins may be produced causing health problems for people, domestic animals and stock that come into contact with the algae. (Water NSW, 2021)

Potential risks.

Contact with the algae by recreational users can be harmful.

Humans and animals should be advised from drinking or swimming in a water body which is suspected of having an algal bloom. (Water NSW, 2021)

There have been reports of skin and eye irritations, nausea, vomiting, muscle weakness or cramps by some people who have swum through algal scum or swallowed it. (CSIRO, 2020)

Read more about Blue Green Algae at:

www.ozgreen.org/br_algae

Algae Identification Key

Image: Willem van Aken, CSIRO

Image: Cooperative Research Centre for Water Qualtiy and Treatment, 2008

1a. If the Bloom is otherwise. Go to 6.

2. Plant fern-like, free-floating with roots. Azolla (Figure 1 and 2).

2b. Plant/algae otherwise. Go to 3.

3b. Free-floating plant with or without hair-like roots. Go to 5.

If you come into contact with water suspected of having blue-green algae, you should remove any affected clothing and wash yourself thoroughly with clean water.

Affected wetsuits should be rinsed in fresh water to remove any trace of algae. If you have any problems, you should seek medical advice. (Health VIC, 2020)

To help identify scums and growths, a simple key can be used. When using this key, make a choice based on the description, then move to the number indicated at the end of that choice. When no numbers are left and a name to the scum is given, you have identified the scum, provided the correct choices were made.

This key is by no means exhaustive, but includes many blooms likely to be confused as blue-green algae.

1. Use a stick to break the scum surface where present and look at the texture. If the scum is composed of many small free-floating plants with or without roots, floating attached plants with roots or algae similar to a flowering plant. Go to 2.

3. Algae superficially like plant: roots absent and has whorled branches. Go to 4.

4. Algae grey-green and secondary branches without whorls of branches. A stonewort (Characeae) of the genus Chara (Muskgrass). Figure 3.

5. Free-floating and differentiated into leaves and stem but not radially symmetrical up to 5 cm in diameter with no roots present. Liverwort (Bryophyte); Riccia or Ricciocarpus. (Figures 5 and 6).

6. Scum composed of strands (filaments) either straight or branched. Go to 7.

6a. Scum otherwise. Go to 9.

7. Filaments green or brown, straight or branched. Go to 8.

7a. Filaments arranged into a hair-net type pattern, possibly the green alga Hydrodictyon (Figure 7 & 8).

8. Filaments in a thick mat, green or brown usually branched. Possibly the green alga Cladophora (Figure 9 and 10) or Enteromorpha (Figure 11).

8a. Filaments green and feel like wet soapy hair, possibly the green alga Spirogyra (Figure 12).

9. Algae one discrete unit, either globular or leaf like: green or brown and not composed of fine filaments or colonies and not paint-like. If broken, it will not reform. A macro algae (Figure 13).

9a. Bloom otherwise. Go to 10.

10. Bloom with a thick paint-like surface or strong colour to water surface. May be green cloudiness or colour to the water. It is not composed of strands or filaments of algae. Go to 11.

10a. Bloom composed of small green, red or brown flecks. May be well spaced or form a thick scum. Go to 13.

11. Bloom blue-green or strong green, possibly a blue-green algae, Anabaena or Microcystis (Figures 14 - 18).

11a. Scum otherwise. Go to 12.

12. Bloom khaki or reddish. May be the green alga Chlamydomonas or the Euglenoid Euglena. Clamydomonas is usually khaki. Euglena can be khaki or reddish and this may change during the day. This should still be checked microscopically as it may be a blue-green algae. (Figures 19-22). Organic matter can also form scums with algae (Figure 23).

12a. Bloom white, grey, yellow-brown, red or blue. May be a mixture of these colours with some green and/or dark humus-type substances included. Possibly a blue-green algal scum after photo-oxidation (Figures 15 and 16). If there is a brown colour to the water it may be a Diatom bloom (Figure 24).

13 . Small flecks on the water surface not uniform in size. May be aggregated to cover a large area or well dispersed. Possibly the blue-green alga Microcystis (Figures 25-26).

(Water NSW, 2021)