Oxford University retracts public health warning

On Wednesday, August 5, signs across University Parks warned that “recent dry weather” had caused an algal bloom, which it said, “may be harmful to humans and pets”.

This comes amid the identification of potential algal blooms across Oxfordshire.

These large growths of algae or bacteria in waterways can be dangerous to human health and fatal to dogs.

Signage near a historic bathing spot read: “Algae in the river.

“Please be aware that there is currently an algal bloom in the river caused by the recent dry weather conditions.

“This may be harmful to humans and pets so it is advisable NOT to enter the water or allow your dogs to do so until further notice.

“Thank you for your understanding.”

After Local Democracy Reporting Service enquiries about what kind of algae was suspected, potential impacts, whether this had been reported to the Environment Agency and if testing had been carried out, a spokesperson for the university said that the signs had been put up “as a precaution” and revealed the parks team “are now confident that this is not a potentially toxic algal bloom”.

(Image: Isabella Harris/LDRS)

They said: “In fact it is duckweed ( Lemna minor ), which has formed a thick mat resembling an algal bloom due to the low water levels, warm conditions, plentiful sunlight and slow river flow.

“Duckweed is native and completely harmless.

“There is therefore no risk to people or animals from poisonous algae – although the very low water levels and poor visibility means entering the water is still a bad idea.”

The signs have since been replaced, but had prompted criticism of water companies and fears about climate change impacts.

Oxfordshire councillors, MPs and campaign groups spoke out, calling for change.

While this algal bloom warning has been retracted, concerns remain about the impact of climate change and drought in Oxfordshire as well as the health of its waterways.

The UK Centre for Ecology and Hydrology’s ‘Bloomin’ Algae maps’ show a “confirmed bloom” in the Farmoor Reservoir, and a “plausible” bloom at the Wolvercote Mill Stream.

The Environment Agency confirmed toxic blue-green algae at a lake in Hardwick Parks in Standlake between Witney and Abingdon.

The Environment Agency’s guidance says that toxin‑producing blooms “can kill wild animals, farm livestock and domestic pets,” and in humans “can cause rashes after skin contact and illnesses if swallowed.”

The NHS in Borders notes that human illness linked to blue‑green algae has included “skin rashes, eye irritation, vomiting, diarrhoea, and pains in muscles and joints” after people swallowed or swam through algal scum, with some cases “severe” but no confirmed deaths.

Veterinary experts are clear that the risk is much higher for dogs.

The Royal Kennel Club similarly says “blue‑green algae can produce toxins that may be deadly to dogs” and advises owners not to let dogs drink from or swim in contaminated water.