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One of the problems that can arise in dams is the growth of algae in or on the water surface.
If you are confronted with an algal bloom in your dam the first thing to do is stay out of the water and do not drink it (even if filtered and boiled).
Then, keep stock away and provide an alternative water supply.
Don't spray water containing algal blooms on to pastures, crops, grapes, vegetables or fruit.

Only a microscopic examination in our laboratory will identify the types of algae present.
We have a special test kit for water samples.

Algae are microscopic plants which inhabit the oceans and waterways of our planet in enormous numbers. All water bodies contain algae and, in low numbers, they present no problems to the user. However, in some places, likely the result of human activities, the balance has been upset. This may culminate in the excessive growth of certain types of algae.

The major pollutants which stimulate excessive algal growth are plant nutrients, nitrogen and phosphorus which are contained in human sewerage, animal manures, fertilizers, detergents and also result from soil erosion. In summer when water temperatures increase, calm conditions prevail and nutrients are available, algae may rapidly multiply creating a slick on the water surface, a bloom.

There are many types of algae that bloom. Most of them are harmless to stock. A severe green algal bloom can seriously interfere with its environment but may not be directly hazardous to people or stock. For example it may cause a fish kill by depleting the oxygen level of the water to the extent that the fish suffocate.

When you see a foul smelling scum which looks like a slick of green acrylic paint along the shoreline of a dam, you are probably looking at a bloom of blue-green algae (BGA). Blue-green algae are not true algae but are more related to the bacteria, Cyanobacteria. Like plants they can manufacture their own food, like animals they can move about in the water to find the most desirable site.

Some types of BGA contain Hepatotoxins, toxic substances which can cause liver damage and gastrointestinal symptoms in both animals and humans. Drinking water containing these toxins can be particularly devastating to stock which already have existing liver damage, perhaps from the ravages of Liver Fluke.

Other types of BGA produce Neurotoxins which can cause nervous tremors, staggering, respiratory distress and paralysis in animals. There have been cases where dogs have died as a result of licking their coats after swimming in a severe bloom of Cyanobacteria.

Endotoxins are another type of toxin present in most species of BGA. These are contact irritants. Swimming in algal laden waters may cause rashes, allergic reactions and persistent coughing in humans and perhaps diarrhoea and nausea in susceptible individuals.

When BGA cells break open and die they release these colourless toxins in large volumes into the water. Eventually, nature does degrade the toxins but meanwhile they can remain active for weeks. This means that water that has had a bloom of BGA on it will not be suitable for use for some weeks after the algae have disappeared.