Blue-green algae at Caerphilly Castle — important guidance for visitors

Monday 30 June 2014

Fishing and other activities involving the moat at Caerphilly Castle have been suspended.

Caerphilly Castle

Caerphilly Castle

We want to warn visitors to Caerphilly Castle that the moat waters currently contain blue-green algae bloom that may be toxic to humans and animals.

We strongly urge our visitors to stay away from the water — and to keep their pets away — as the toxins the algae produce can cause severe illness.

Fishing and other activities involving the moat at Caerphilly Castle have been suspended.

What are blue-green algae?

There are a wide range of blue-green algae (cyanobacteria). In fresh waters, they’re suspended within the water or attached to rocks and other surfaces.

Blue-green algae and other algal groups are important contributors to the aquatic biology of fresh and marine waters.

They are primary producers that:

  • convert sunlight to energy by photosynthesis
  • release oxygen and carbon dioxide into water
  • take up minerals
  • produce food chain supporting substances.

Blue-green algae need nutrients to grow which exist in various forms in freshwater. The algae use them directly.