Commonly referred to as blue-green algae, the cyanobacteria are photosynthetic bacteria which contain chlorophyll and various accessory pigments. Common in aquatic habitats they play a major role in the nitrogen, carbon, and oxygen dynamics of these environments.
Ecologically, there are a number of major groups: mat-forming species, which form biofilms over rocks, sediments, and submerged plants; colonial species, some of which can form blooms in nutrient-rich (eutrophic) lakes; and picocyanobacteria, which are extremely small cells that are often abundant in clear water lakes. There are also species that form aggregates that are loosely associated with emergent water plants such as rushes and reeds, and those that grow on the surface of plants and hard substrates in aquatic environments. Some species also form complex symbiotic relationships e.g. with fungi and other algae in lichens.
Although widespread in aquatic habitats throughout the islands, there is very little published information on the range of species and their distribution. Outer Hebrides Biological Recording have recently started recording cyanobacteria and would welcome further records.