Algae & Algal Blooms
Rural Chemical Industries (Aust.) Pty Ltd.
- What Are Algae?
- What do they look like?
- Types of Algae
- Problems associated with Blue-Green Algae
- Causes of Blooms
- Related Information - How to Control Algae
What Are Algae?
There is no easy definition of an alga. Algae are generally microscopic organisms, are generally thought of as simple aquatic plants which do not have roots, stems or leaves and have primitive methods of reproduction. 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.
Learn all you need to know about algae and how to control them with RCI Coptrol.
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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 kelps (metres in length) to those visible only under a microscope.
What do they look like?
Algae vary considerably in size, shape, and growth form.
They can be:
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Main habitat preferences are:
- 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 macroalgae (eg. seaweeds).
Types of Algae
The main groups of algae found in Australian freshwater are:
- Green algae (Chlorophyceae)
- Diatoms (Bacillariophyceae)
- Euglenoids (Euglenineae)
- Blue-green algae (Cyanophyceae)
However there are also other less common groups of algae that do occur in freshwater...
Green Algae
Green algae range in size from microscopic to large plants, and can be 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 with. 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
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 do, they release oxygen. They grow in dams, rivers, creeks, reservoirs, lakes and even hot springs.
Blue-Green Algal Blooms
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.
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.
Blue-green algal blooms happen when there are high nutrient levels, low flows in rivers, low wind and high temperatures. There was a severe blue-green algal bloom over 1000 km long in the Barwon-Darling River system in October and November of 1991. This bloom impacted greatly on water supplies, agriculture, fish and aquatic animals, tourism and recreation.
Problems associated with Blue-Green Algae
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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. However, many stock deaths have been documented. 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.
Toxic Blue-green algae
The four main toxic blue-green algae in Australia are:
- Anabaena,
- Microcystis,
- Cylindrospermopsis and
- Nodularia.
Anabaena, and Microcystis are the two main bloom-forming genera in NSW waters. Anabaena forms long chains of cells, called a trichome, which sometimes grows in a spiral, depending on the species.
Microsystis 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 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 New South Wales. 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.
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 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.
Related Information - How to Control Algae
Contact us to discuss how our algicide product Coptrol can help you control algae in all circumstances including:
- Ornamental ponds and Golf courses
- Stations & Mining operations
- Sewage treatment works, power
- Household water supplies
- Farm dams & Stock troughs
- Rice crops
- Aquaculture
- Swimming pools
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PO Box 6316 The South Sydney Business Hub Alexandria Sydney, NSW 2015 Australia |
Unit 5, 7-9 Kent Road Mascot Sydney, NSW 2020 Australia |
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