Blue-Green Algae produce a variety of toxins, with some species producing several toxins. The most common blue-green algae in the UK is Microcystis aeruginosa, which produces a toxin generically know as a hepatotoxin. The test kits can detect the most common, and most toxic of the hepatotoxin, namely Microcystins-LR. The other common toxin in the UK is Anatoxin-a, which is a neurotoxin and principally impact the nervous system.
In the UK, pets and livestock are the most reported cases of fatal or near fatal poisonings. The impact on dogs can be swift, especially if they drink from blue-green algae water on a hot day. The fatal impact on people is thankfully limited, but fatal poisonings have occurred at 20ug/l for Microcystin (WHO, 1999). The most likely symptoms for people exposed to cyano-toxins ranges for skin irritations through to chronic and prolonged illness as a result of the ingestion of cyano-toxic water. Further technical information is available from US National Library of Medicine, National Institute of Health.
Learn more about blue-green algae
Many forms of algae are non-toxic and are critical to the life of freshwater. Thousands of species of invertebrates and fish depend on the algae. But when water gets too hot, deoxygenated or nutrient rich, "blue-green algae" which is a bacteria, can start to dominate the ecology of a lake.
The table below, generated by the Health Protection Agency (2012), lists the common health effects of cyano-toxins. Microcystin-LR and Anatoxin-a are the two most likely toxins in UK waters. Cylindrospermopin toxin is associated with cyano-bacteria found on the bed of a lake or pond and is less common. The test strips are available for these three cyano-toxins.
Algae blooms can form quickly in calm periods, typically after a series of warm days that heat up water. Blooms in the UK occur throughout the Spring to late Autumn, with more nutrient rich water and shallower features becoming more prone to blooms. Blooms can occur for a few days to several weeks. The blooms can be dispersed in windy weather, but the algae and associated toxicity of the bloom peaks when the bloom is dying and scums of dead cells form on the lake. This is when the toxins are released from the bacteria cells.