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Stratford-on-Avon District Council
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Water - Blue/Green Algae

Blue/Green Algae

Blue Green Algae are not true algae, but are more properly photosynthetic bacteria and can also be called cyanobacteria. They are commonly found in lakes, ponds and wetlands. They usually occur in small numbers and are invisible to the casual observer. When conditions are favourable (most often during hot, calm weather), algae increase dramatically and they become easy to see. This condition is generally called a 'bloom'. When blue-gree algal blooms occur, huge numbers of algae accumulate on the surface of the water resembling thick 'pea soup' and are often blue-green in colour. As well as being unsightly, blue-green algal blooms may be toxic if ingested by wildlife, livestock or humans. After ingesting water containing toxic blue-green algae, skin rashes, symptoms such as fever, dizziness, stomach cramps, vomiting or sore throat may persist for several days in humans.

Watercolour of the pond, Bitham Hall

When blue-green algae is identified in a water feature and is above the World Health Organisation threshold for recreational waters, warning notices are positioned around the body of water and restrictions placed on access until the concentration of algae have returned to a safe level.

The Environment Agency provide information regarding blue-green algae and you can contact them at:

Sentinel House, Wellington Crescent, Fradley Park, Lichfield, Staffs WS13 8RR

Telephone: 01543 4048826