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Identifying algal blooms

Identifying algal blooms

Identifying algal blooms

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. 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.

Humans and animals should be advised from drinking or swimming in a water body which is suspected of having an algal bloom.

How to report algal blooms and the actions that should be taken by the various agencies are outlined in Regional Algal Contingency Plans available from the RACC Secretariat in your area.

Key to blooms

To help identify scums and growths, a simple key can be used. Follow the steps below to find if the scum is possibly caused by excessive blue-green alga, another alga or by an aquatic plant. It is necessary to go to the surface of the scum to do some simple tests.

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.

Start

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.

1a. Bloom otherwise. Go to 6.

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

Plant fern like, free floating with roots. Azolla
Figure 1 (Geoff Sainty).

Plant fern like, free floating with roots. Azolla

Figure 2 (Simon Mitrovic).

2b. Plant / algae otherwise. Go to 3.

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

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

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

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

4b. Algae greener in colour and secondary branches with whorls of branches. A stonewort (Characeae) of the genus Nitella. Figure 15.

5. Free-floating plant with or without hair-like roots. Plant small, less than 2 cm long. A Duckweed being the genera LemnaWolffia, or Spirodela (Figure 4). The small leaved Wolffia does not have roots but is a small plant c. 1 mm in diameter.

A Duckweed being the genera Lemna, Wolffia, or Spirodela
Figure 4 (Geoff Sainty).

5b. 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 & 6).

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

Figure 5 (Surrey Jacobs).

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

Figure 6 (Surrey Jacobs).

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).

Filaments arranged into a hair-net type pattern, possibly the green alga Hydrodictyon

Figure 7 (Simon Mitrovic).

Filaments arranged into a hair-net type pattern, possibly the green alga Hydrodictyon

Figure 8 (Simon Mitrovic) .

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

Filaments in a thick mat, green or brown usually branched. Possibly the green alga Cladophora

Figure 9 (Simon Mitrovic).

Filaments in a thick mat, green or brown usually branched. Possibly the green alga Cladophora

Figure 10 (Simon Mitrovic).

Spirogyra
Figure 11 (Simon Mitrovic).

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

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 the broken it will not reform. A macro algae (Figure 13).
macro algae
Figure 13 (Simon Mitrovic)

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).

Anabaena
Figure 14 (Bruce Cooper).

blue-green
Figure 15 (Peter Bek).

green cloudiness
Figure 16 (Simon Mitrovic).

colour to the water
Figure 17 (Simon Mitrovic) .

Scum
Figure 18 (Peter Bek).

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).

Euglenoid
Figure 19 (Simon Mitrovic).

Euglena
Figure 20 (Geoff Sainty).

Clamydomonas
Figure 21 (Geoff Sainty).

Euglena
Figure 22 (Simon Mitrovic).

scum
Figure 23 (Simon Mitrovic).

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).

Diatom
Figure 24 (Simon Mitrovic) .

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).

Microcystis
Figure 25 (Simon Mitrovic).

Microcystis
Figure 26 (Simon Mitrovic).

This key is by no means exhaustive, but includes many blooms likely to be confused as blue-green algae. The algae here are generally found in freshwater systems such as lakes, rivers, reservoirs, creeks and ponds.

86.5
Tuesday 17 October
-0.7
2,232,940 ML
2,581,749 ML
6,780 ML
969 ML
-15,492 ML
Tuesday 17 October