Dictionary of Environmental Health
A term used to describe certain types of potentially toxic vegetative growths of algal appearance. The term is a misnomer in that the organisms are really a type of bacteria. They exhibit some of the same properties of true algae however and are scientifically more correctly termed cyanobacteria. They have a worldwide range from the arctic to the high temperature areas around hot springs where few other life forms can survive.
Many blue-green algae are capable of fixing nitrogen and are therefore able to out-compete other algae, becoming the dominant species, especially in warm, calm conditions. They generally proliferate in waters that have high nutrient levels (EUTROPHIC) and are less abundant in waters with a low nutrient level (OLIGOTROPHIC).
At certain times abnormal growth of these organisms can lead to the production of what is known as a ‘bloom’, essentially the development of a dense colony. These blooms have the potential to produce toxins that, if ingested (especially) by filter-feeding shellfish, can lead to toxin accumulation and subsequent poisoning if the contaminated shellfish are eaten. Although not all blue-green algae produce toxin and not all blooms prove to be toxic it is wise to assume that all blooms are potentially toxic.
See also: AMNESIAC SHELLFISH POISONING; DIARRHETIC SHELLFISH POISONING; PARALYTIC SHELLFISH POISONING
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