What are algae?

There is no easy definition of an algae. Algae are generally microscopic organisms, are usually thought of as simple aquatic plants which do not have roots, stems or leaves and have primitive methods of reproduction.

They are carbon fixing and oxygenating organisms. However some algae display primitive animal features such as motility, while blue-green algae differ markedly from plants and all other algae, in that they have a cellular structure and function that is more common to bacteria than to the plant kingdom.

Algae live in a wide range of aquatic environments and are a natural component of most aquatic ecosystems. Additionally, a great many are also terrestrial, living in soil, snow, or in association with other organisms, especially fungi (as lichens),and animals. Aquatic algae are found in both fresh and marine waters. They range in size from large kelp (metres in length) to those visible only under a microscope.

Some algae have an economic importance because they are a source of carotene, glycerol, and alginates and can be converted into a food source for aquaculture.

What do they look like?

Algae vary considerably in size, shape, and growth form.

They can be:

  • Single celled
  • Many celled – either colonially or as filaments of cells; or
  • Elaborate plant bodies with differentiated cell types

Main habitat preferences:

  • Free floating in the water column (planktonic). These comprise the microscopic unicellular algae and colonial and filamentous algae, known as “phytoplankton”.
  • Growing as a film on rocks on the bottom (benthic) or on plants growing in the water (epiphytic). These may be single celled or small colonial and filamentous species.
  • Growing out into the water column but attached to a substrate at one point. These comprise the larger filamentous algae, and macro algae (e.g. seaweeds).

Types of algae

The main groups of algae found in Australian freshwater are:

Click on the images below for further details.

Green Algae Diatoms algae
Euglenoid algae Blue Green Algae

However there are also other less common groups of algae that do occur in freshwater.

  • Golden Brown Algae (Chrsophyta)
  • Crytomonads (Cryptophyta)
  • Dinoflagellates (Dinophyta)
  • Glaucophyta
  • Brown Algae (Phaeophyta)
  • Haptophytes
  • Red Algae (Rhodphyta)
  • Yellow-Green Algae (Tribophyta)

Identifying the algae to be treated.

Generally speaking, Coptrol will control all free floating and filamentous green algae including brown slime. The most common species of algae are:

Green Algae

Free floating – these are microscopic plants usually existing in suspension in the upper 60 – 90 cm of water often reaching bloom proportions making the water appear brownish or pea soup green. The natural die-off of this form can cause summer fish kills due to depletion of dissolved oxygen. Some species are known to be toxic to livestock, wildlife, and man or impart odour and taste problems.

Euglena Infestation algae complete

Euglena, sp. Is widespread and often abundant. Euglena sp reproduce rapidly and are especially common in warm seasons.They are commonly found in freshwater streams and ponds, when they may form a green scum on the surfaces of storages,irrigation bays or drainage ditches. They are green and sometimes red. They occasionally form green or red powdery films on the surface of ponds or dams. The surface colour can change from red to green in a few hours. Euglena is free swimming in ponds and lakes and is also found in mud rich in organic matter. There are 152 reported species 33 known to occur in Australia.

Microcystis algae complete

Microcystis, (Anacystis) is probably the most common toxic algae occuring in farm dams, usually form greenish-yellow bubbly masses in still or nearly still water. The plant cells are arranged like a small hair net. A blue green algae has numerous small cells crowded within a gelatinous matrix, forming a colony which may be ovate (like an egg) or an open meshwork. Microcystis is found free floating in lakes, reservoirs and sometimes in slow flowing rivers. Colour ranges from blue-green or yellowish brown. The colonies are usually globular. A hint of red can often be seen. It is a common cause of algal blooms and can secrete chemicals that inhibit other algae. It can also produce a polypeptide which is toxic to animals after drinking contaminated water. It has also been implicated in human illnesses including necrosis of the liver (after drinking) and severe dermatitis (after contact),etc. There are 40 reported species 7 known to occur in Australia.

Anabaena algae

Dictyosphaerium Anabaena, are a blue green species which grow in spirally coiled filaments, both species often occur as water blooms which can be concentrated by wind action. It is one of the toxic blooms forming blue green alga. It is coloured grey to blue-green or even green and is free floating in slow flowing or still waters. It sometimes forms a gelatinous mass. It most often occurs throughout late spring to autumn. Some species can produce an alkaloid (similar to cocaine) which acts as a neuromuscular blocking agent causing respiratory arrest, liver and gastro intestinal damage. It may also cause cancers. Species containing this alkaloid is highly toxic and animals may die soon after drinking water containing the toxin. Some blooms also cause contact irritation leading to severe dermatitis. There are approx. 70 species worldwide 29 occurring in Australia.

Nodularia algae

Nodularia is part of the Blue Green Algae (Cyanobacteria) family and is widespread. Blue greenish in colour. Usually found free floating in salt, brackish and freshwater lakes, dams and ponds. It is frequently intermingled with other algae forming extensive blooms. These blooms can cause death of stock or native animals. Nodularia produces hepatoxins that can kill liver cells, causing liver damage and gastro enteritis in humans. There are 12 known species one reported in Australia

Oscillatoria algae

Oscillatoria, is part of the Blue Green Algae (Cyanobacteria) family. It is blue greenish in colour, usually free floating, cylindrical or sometimes slightly tapering, unbranched filaments in aquatic environments. Some are tolerant of high levels of organic pollution and some are shade-tolerant and able to survive in water below blooms of green algae. It is implicated in irritation of skin and mucous membranes suffered by people swimming. It is widespread and common in a variety of habitats. There are approximately 150 known species of which 47 are known to occur in Australia. Some species causes contact irritation leading to severe dermatitis.

Filamentous algae

Filamentous also known as “pond moss” or “pond scum” these threadlike algae often occur in huge greenish masses floating upon the waters’ surface.They can form dense mats in static water or long, rope-like strands in flowing water. Its filaments consist of series of cells being joined end to end giving a thread-like appearance. This form begins growing on the bottom or substrate and then lifts to the surface as buoyancy grows due to its production of oxygen. This form of algae may seem cottony, slimy, or coarse in texture.

Spirogyra algae

Spirogyra, very common green algae which feel like wet, soapy hair, bright green in colour often found free floating in static water near the surface or in masses in the sediment. Sometimes forms extensive mats in rivers, dams, ponds and often blocks channels. There are 300 known species 47 reported in Australia.

Chlorella algae

Chlorella, a small grass-green plant which usually stores starch.

Hydrodictyon Bloom algae

Hydrodictyon, The plant cells are arranged like a small hair net. Usually found free floating in lakes, dams, ditches and slow flowing streams. It can become a real nuisance choking small streams and drains. There are 6 known species one reported in Australia.

Chara algae

Chara – dark grey-green with orange or green pinpoints on the branches. Chara often grows at the bottom of lakes in fresh and also some brackish waters one to six metres deep. Chara is common in freshwater areas with silty or sandy beds. It is usually more noticed in droughts when the water level drops. There are 19 known species 16 reported in Australia.

Nitella algae

Nitella – thrive in water less alkaline than Chara. The plants are greener and are distinctly branched. Both are found in rice fields when the crop is thin. Similar to Chara. Nitella is common in freshwater areas with silty or sandy beds especially in clean water. It is green and found attached in sand and soil in still and flowing freshwater and occasionally in brackish waters.  There are about 180 known species 24 reported in Australia. Mats of Nitella and Chara have a wiry, coarse texture as well as a slightly fishy odour.The common name for these algae is stonewort due to the very coarse, sandpapery feel to the mats.

Oedognium algae

Oedognium – A free floating green filament usually attached to rocks in still or moving water. Also found on wood and some aquatic plants. There are approx. 400 known species 70 reported in Australia.

Phormidium algae

Phormidium – Is widespread. It is blue greenish in colour usually attached to rocks, debris or sediment in fresh and salt water. Sometimes found on damp soil. The filaments form a consistent mass. Approx 49 species 20 reported in Australia.

Green Algae

Green algae range in size from microscopic to large plants, and canbe single celled, colonial, or filamentous. Some of the single celled and colonial green algae have small tails or “flagella” attached to each cell, which they use to swim. However many green algae are non-motile. Green algae may be either planktonic or attached. They show the greatest diversity of shapes, sizes and species of any group of freshwater algae. Green chloroplasts are frequently observable within the cells of green algae when looked at under a microscope.

Blue green algae bloom


Blue Green algae

Blue-green algae or Cyanobacteria are microscopic cells that grow naturally in Australian fresh and salt waters. They are a type of bacteria, but in some ways act like plants by using sunlight to manufacture carbohydrates from carbon dioxide and water, a process know as photosynthesis. In doing so, they release oxygen. They grow in dams, rivers, creeks, reservoirs, lakes and even hot springs.

When blue-green algae bloom, that is, grow to large numbers, they can form thick accumulations on the surface of the water. These accumulations are commonly known as scums. Blue-green algal scums form when large numbers of the algae float to the water surface using vesicles within their cells that they inflate with gas. Coming close to the surface enables them to gain maximum sunlight.

Nostco bloom

Wind pushes the floating algae across the water, concentrating scums against leeward shores. Scums can vary from small dots (blue-green algal colonies) resembling green dust floating on the water at the beginning of a bloom, to thick paint-like accumulations on the surface during the height of a bloom. Blooms are often green or blue-green but can also be white, brown, blue, yellow-brown or red. Wind movement, bleaching by sunlight, and other blooming algae, can cause swirling patterns of a mixture of these colours in scums. While the problem is not new, it has increased in recent times because of our land and water management practices and seasonal droughts.

Cladophara bloom algae

Water affected with blue-green algae usually smells and tastes unpleasant so that people are unlikely to drink it, however, take care to avoid skin contact, see the blue-green algae safety checklist below for further details.

Blue-green algal blooms happen when there are high nutrient levels, low flows in rivers, low wind and high temperatures. When severe blue-green algal blooms span vast distances in River systems, impact on water supplies, agriculture, fish and aquatic animals, tourism and recreation are greatly affected.

Filamentous algae

Problems associated with blue-green algae

  • Unpleasant Odours & Tastes.
  • Filters on pumps and machinery clog.
  • Large fluctuations in pH.
  • De-oxygenation due to decomposition endangers fish.
  • Increased costs of operating water treatment plants.
  • Poor aesthetics spoil recreation and tourism.
  • Poisoning of humans & livestock.
  • Skin irritation in humans.

Blue green algae bloom

Blue-green algae produce highly potent toxins

The main cause of concern about blue-green algae is the ability of some to produce highly potent toxins. There are four different forms of toxins that can be produced:

  • Hepatotoxins: These attack the liver and other internal organs of the poisoned victim. Some have also been identified as cancer promoting substances.
  • Neurotoxins: These act as neuromuscular blocking agents, leading to respiratory arrest.
  • Endotoxins : These are contact irritants, and can cause severe dermatitis and conjunctivitis in people coming into contact with the algae through swimming or showering. They may also cause  stomach cramps, nausea, fever and headaches if consumed. Their presence in airborne droplets can cause asthma. Some are also thought to be possible tumour promoters, although this has yet to be shown.
  • Non-specific toxins: These are relatively slow acting  general toxins which progressively damage most organs, including the liver.

Stock deaths

In Australia no recorded human deaths have been attributed to blue-green algal toxins. The best documented case of human deaths occurred in Brazil, where around 75 dialysis patients died after direct exposure to toxins in their dialysis fluid. However, many stock deaths have been documented. The first scientifically documented case of an algal bloom causing deaths was in South Australia’s Alexandrina in 1878, where cattle, pigs and sheep died within hours of drinking contaminated water. The toxins produced can persist in water for weeks. The toxins can also be concentrated by shellfish, which poses a potential health risk if they are consumed.
Click here for more information on livestock and blue green algae.
Blue green algae bloom

Toxic blue-green algae

The five main toxic blue-green algae in Australia are: Anabaena, Microcystis, Cylindrospermopsis, Oscillatoriaand Nodularia.

Anabaena algae

Anabaena, and Microcystis are the two main bloom-forming genera in Australian waters. Anabaena forms long chains of cells, called a trichome,(hair like structure) which sometimes grow in a spiral, depending on the species.

Microcystis aeruginosa is most common in lakes and reservoirs. It forms irregularly shaped colonies of cells up to 1 to 2 mm wide that can be visible to the naked eye. Microsystis blooms can be quite persistent lasting for months, or even years in some cases.

Nodularia algae

Nodularia often forms thinner scums than those of Anabaena and Microcystis blooms. Nodularia, like Anabaena, forms chains of cells or trichomes. Although it occurs in fresh waters, it is more common in brackish waters.

Cylindrospermopsis is commonly thought of as subtropical blue-green algae, but it also occurs in more temperate regions during the summer, including parts of Australia. It has very tiny cells that form chains or trichomes. It is a freshwater species, and causes problems in town water supply systems due to its highly potent toxins.

oscillatoria algae

Oscillatoria is blue greenish in colour, usually free floating or entwined with other algae. It is widespread. There are approximately 150 known species of which 47 are known to occur in Australia. Some species causes contact irritation leading to severe dermatitis.

Irritant Blue-green algae

Not all blue-green algal species are toxic, and even different strains of the same species may differ, with some being highly toxic and others non-toxic.  All blue-green algae however, contain lipopolysaccharides, which act as contact irritants, Even if the other more potent blue-green algal toxins are not present, the presence of these contact irritants may make the water unsuitable for body contact or recreation if the blue-green algae are present in bloom proportions. A number of other blue-green algae have been shown to be toxic overseas, but not yet so in Australia. Therefore these too should be treated with caution when present in bloom proportions.

Causes of algae Blooms

High nutrient load

Blue-green algal blooms are natural phenomena and while it is not exactly clear what triggers a bloom, excess human sources of nutrients such as fertilisers and sewage certainly can increase the intensity of blooms (i.e. greater number of algae).

Thermal stratification

One of the most important factors triggering blue-green algal blooms appears to be a lack of mixing of surface and deeper water layers in a river or reservoir. In lakes and reservoirs mixing is mainly controlled by wind and temperature. Through the summer months the surface waters heat up resulting in a warmer top layer and cooler bottom layer which do not mix. In rivers, mixing is mainly caused by flow. Flows from headwaters can decrease or stop during drought conditions allowing thermal stratification to develop. Weirs and extraction of water for irrigation and stock watering also reduce flow in rivers.

Algae float to surface

Some blue-green algae can float to the surface under these conditions having access to all the light in the top waters (photic region) and nutrients in the top and bottom waters. This allows the algae to flourish and bloom. Some other algae are motile and can swim to the photic region under these conditions.

Many other factors play a role in the formation of blue-green algal blooms including temperature, salinity, zooplankton grazing, pH and turbidity.

Strategies for preventing blue green algal blooms

The best way to so prevent algal blooms in farm dams or ponds is to reduce the amount of nutrients and sediments entering the dam.
Here are some ways to achieve this:

  • Establish or improve the growth of aquatic plants in the dam. The plants will compete with the cyanobacteria for the vital nutrients they both need.
  • Make sure you do not use any of the introduced species of aquatic plants that are declared pests.
  • Establish perennial grasses and trees upstream and around the dam to intercept and trap nutrients and sediment.
  • Manage stock access to the dam. The most effective solution is to fence the dam off completely and pipe the drinking water to troughs in the paddock.
Blue-green algae safety checklist

  • Regard blooms as toxic until water is tested.
  • Avoid skin contact: wear rubber gloves when collecting.
  • Inspect all dams, ponds, troughs regularly in hot weather.
  • Isolate all people and stock from affected areas.
  • Make sure an alternative drinking water supply is available to stock.
  • Contact veterinarian if animals show symptoms of poisoning. There are no effective antidotes to cyanobacterial poisoning but it is possible to prevent absorption of the toxin provided the vet is called quickly after ingestion.
  • Boiling algal water will not make it safe.
  • Algaecides used to kill blue green algae DO NOT kill the toxins in the algae.
  • Blue green algae toxins are colourless, odourless, and remain toxic  for at least 3-4 weeks. They will eventually degrade through microbial activity.
  • U.V. light does not degrade blue green algae toxins
  • Use of biocidal chlorine does not degrade the toxins
  • Do not use water that has blue-green algae in it on plants being grown for human consumption, particularly for spray-irrigated salad and leafy vegetables, because dried algal cells on the leaves can remain toxic for several months.

    Do not:
  • Drink or swim in it.
  • Rinse feedstuffs in it. Eat fish, shellfish, etc caught in affected water.
  • Spray or irrigate crops with it.

Livestock and Blue Green Algae   

If a farm dam is affected by any of the cyanobacteria (Blue Green algae). It is important to ensure livestock (this includes all livestock including dogs, cats, poultry, pigs, horses. goats, sheep and cattle etc.).

Do not:

  • Drink the water Eat mats of dried algae left along the shoreline
  • Drink the water treated to kill blue green algae for at least a month because dead or ruptured cells of cyanobacteria release poisonous toxins.
  • Drink from the scum left along the shoreline because the scum is especially toxic.

Symptoms of poisoning

Animals can exhibit a variety of symptoms. The most common being:

  • Muscle weakness
  • Lethargy
  • Reduced or off their feed
  • Paleness
  • Mental derangement
  • Diarrhea
  • Serious cases will be generally distressed, suffer muscle tremors and coma and die within a few hours or days.