Blue-green algae

Blue-green algae – or cyanobacteria – are bacteria rather than true plants. Their green, red and blue pigments appear blue-green to us.

Blue-green algae can form blooms and certain species are toxic. They are present in many bodies of water, in low numbers.

Some species of blue-green algae can:

  • collect gas within their cells – which allows them to move up the water column to better locations for collecting light and nutrients
  • fix nitrogen in special cells called heterocysts – the number of these cells increases when nitrogen levels in the water are low

Find out more about cyanobacteria on the NBN Atlas Scotland website.