A natural part of the aquatic ecosystem

Algae is a natural part of the aquatic ecosystem with most species safe or non-toxic. However, some algae can produce toxins that can be damaging to humans, domestic animals and livestock that drink or come in contact with the water, and also organisms living in water. These algae can be found in freshwater as well as marine and estuarine waters.

Blue-green algae (also known as cyanobacteria) are the only group of algae known to be toxic in freshwaters. They are microscopic bacteria living in water, and are capable of photosynthesising which is why they are often called algae. Though microscopic, when they form colonies and accumulate together they can become visible to the naked eye. Blue–green algae can produce potent liver and neurotoxins as well as skin irritants. However, not all blue–green algae are toxic, and even toxic species do not always produce toxins.

Many blue-green algal species are able to regulate their buoyancy and can sometimes be seen as green scums on water, or they just colour the water green.

Toxic marine and estuarine algae can also affect recreational water use. Some of these algae produce toxins that can cause illness, particularly if contaminated shellfish is ingested, and others can cause skin irritations. These algae often cannot be seen, but some cause red discolouration to water a phenomenon known as red–tides.

To find out more about our role in managing algal blooms please visit Water services - Algae.

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