The flourishing of blue-green algae in the current heatwave has prompted a spate of reports of the potentially toxic blooms via the Bloomin’ Algae app - launched exactly a year ago. Professor Laurence Carvalho, a freshwater ecologist at the Centre of Ecology & Hydrology, who helped devise the app, explains why.

The long hot and dry summer has provided ideal conditions for the growth of blue-green algae - also known as cyanobacteria – which poses a health risk to people and animals who come into contact with or swallow infected water.

Our Bloomin’ Algae app enables users ­- including dog walkers, swimmers, boaters, anglers and anyone else near fresh water - to submit a photograph of the bloom and its location, so the potential risks to people and animals can be gauged.

Blooms have been spotted at a number of water courses across the UK, including parts of the Lake District, with members of the public warned about toxic algae.

It can cause damage to the liver or nervous system and there have been reports that at least three dogs have died over the summer after coming into contact with blue-green algae – two in Scotland and another in Sussex.

People who have swam through or swallowed algal scum can suffer from skin rashes, eye irritation, vomiting, diarrhoea, fever and muscle and joint pain, though there is no evidence that these have led to long-term effects or deaths among people in the UK.

There were more than 700 downloads of the app in the first three weeks of July across the UK, with about 80 reports made via the Bloomin’ Algae app. When the app was first launched exactly 12 month ago, there were about 90 app downloads a week and 32 records for July 2017. 

However, not all these reports have been verified as being blue-green algae, which are microscopic but can clump together to form thin wispy green blooms or thick paint-like scums. Some photos indicate that harmless duckweed and other stringy hair-like algae (‘blanket weed’) are also being confused by the public with blue-green algae. The app provides a guide to help distinguish some of these.

The location of verified sightings are passed to the relevant environment agency. However, anyone spotting suspected blue-green algae is also asked to report the incident directly to the local authority if there is not already a warning sign at the site.

Blue-green algae has been a particular problem this year because the hot weather has encouraged their growth, while the long dry spell means they are not flushed out of water courses.

We are receiving a large number of reports via the app, which aims to provide an early warning system and speed up the process whereby local authorities or the landowner put up signs at sites to alert the public and pet owners of the risks.

We would urge people making a report via the app to also include a photograph and the correct location, so it can be verified as being blue-green algae. We also recommend they register an email address so they can receive feedback on their records.

The Bloomin' Algae app was created last year by CEH in collaboration with the Scottish Environment Protection Agency, Health Protection Scotland, the Environment Agency in England and Public Health England.


Download the app via iTunes for Apple products or by Google Play for Androids

You can view sightings on the Biological Records Centre website

Staff page of Professor Laurence Carvalho