6 Facts about Cyanobacteria : Blue-Green Algae

Blue-Green Algae?

It is also called Cyanobacteria. They are cluster of photosynthetic bacteria which are commonly called “pond scum”. They are mostly blue-green in color & also appear in blue, green, brown, reddish-purple. Normally they develop in water of ponds, lakes & different slow-moving river while water is moderately hot & rich in nutrients such as phosphorous & nitrogen.  In favorable environmental condition blue-green algae may quickly develop in number. Maximum species are light in weight & float to the substratum when they create a layer of scrum which is typically known as “blue-green algal bloom”. Blue-green algal blooms mostly occur in Wisconsin between mid of June to late September; exceptionally they may grow during winter under ice. There are various Blue-green algae species in water of Wisconsin but typically identified species are: Planktothrix sp, Anabaena sp and  Microcystis sp. With seasonal changes different species may develop in the water bodies.


Cyanobacterial Toxins:

They are naturally formed toxins preserved in cells of particular species of Cyanobacteria. There are different kinds of toxins. Some may damage liver (hepatotoxins) or nervous system (neurotoxins), or other may causes skin irritations. With the breakage or destruction of cells these toxins are discharged into water bodies. Scientists of Health Canada are especially bothered for hapatotoxins than neurotoxins as hepatotoxins are more widely spread in water supplies than neurotoxins. Till now few Cyanobacterial toxins have been detected & characterized. Better ways of identification are being developed which will help us to study about them, particularly helps in finding which toxin is harmful in Canada & what are the favorable condition for their growth.


It is a class of toxins produced & discharged by Cyanobacteria as they were separated from a cyanobacterium known as Microcystis aeruginosa. Microcystins are common types of Cyanobacterial toxin typically found in water & are responsible for causing harms in animals & humans those who come in contact with poisonous bloom. They are highly stable in water due to their chemical structure & are able to sustain both in cool & warm water.

Difference between true algae & blue-green algae:

Like typical algae the Blue-green algae also a part of phytoplankton in different water bodies but they are not feed by other organisms which makes them unimportant in food-chain where true algae are a major part of food-chain as “primary producer”.

Concerns related with the blue-green algae:

Concerns related with the blue-green algae involve discoloration of water, decreased light penetration, problems in taste & odor, deficiency in dissolved oxygen at the time of die-off & production of poisonous substances. Water discoloration is an esthetic concern, but when it becomes dense blue-green algal bloom it prevents penetration of light which in turn affect aquatic ecosystem directly (phytoplankton & other aquatic weeds) as well as indirectly (zooplankton & fishes). It is actually smelly so people should not drink impure water. When these bloom die-off, the cells of algae sink & decomposed by microbes. The decomposition process needs oxygen which in turn decreases dissolved oxygen that extensively affects aquatic ecosystem including fishes & may even results in destruction of fishes.

The poisonous substances of blue-green algae are chemical compounds which form naturally within cells of some species. There is particularly no fixed time of this toxin production. When these cells die-off or decomposed the toxin is released into the water of lake/pond. Release of toxin may also occur if water is examined with chemicals in order to kill the algae & when these cells are consumed by other organisms and it mixes with the digestive acids. So in order to make sure about the toxicity of water, the water sample must be studied in laboratory using advanced equipments.

Causes of bloom appearance at night:

If we cannot see a Cyanobacterial bloom staying afloat on water substratum it doesn’t mean that bloom is absent rather the blooms are hanging at different depth of water where we cannot see. This water level at which Cyanobacterial bloom resides depends on several factors like light, phosphorous & nitrogen. They require these factors for their survival. With the environmental & seasonal changes Cyanobacteria can control their tendency of floating. They can move from one region to another (by floating or sinking) depending on the level of available nutrients & light. For this movement Cyanobacteria require light. In absence of light cells can not adjust their floating tendency & may float to the substratum producing surface scum.  Actually this scum appears at night & moves around the water when wind & waves disperse the cells.



Prita Banerjee

She has joined Srijee Innotech Pvt Ltd. as a Content Developer from Last week of June'2013. She has completed her MCA on July'2013 from Punjab Technical University. She has done her MCA final 6th SEM major project  in ASP.net using C# on February'2013. She has done her graduation in 2007 with Zoology hons from Calcutta University..After completion of her graduation she worked at Project impact,Jadavpur University as Part time faculty of Computer fundamentals & Basic Programming. She also worked as a Project Tainee at NIVT,Kolkata from Aug'2012-Jan'2013...

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