Seaweeds of the Outer Hebrides

Rocky coasts, sandy shores and salt marshes all have a characteristic flora but apart from a small number of highly specialised vascular plants and lichens which are tolerant of salt and periodic flooding, the area below the mean high water mark is dominated by algae. In shallow coastal waters the macro algae or seaweeds dominane and in terms of biomass they are the most abundant form of marine life.

The British seaweed flora comprises of more than 600 species which are divided into three main groups - Chlorophyta (green marine algae); Ochrophyta (brown seaweeds which includes the wracks and kelp); and the Rhodophyta (red marine algae). The colour of the seaweed is caused by differing combinations of photosynthetic pigments which determines their ability to absorb light of differing wavelengths and hence reflects their distribution within the tidal zones of the shore. However, it is the combination and interaction of life history, ecological and biochemical characteristics which defines their actual distribution.

The marine algae are an important part of the seashore ecosystem providing habitats and shelter for invertebrates and food for herbivores and other invertebrates.

So far we have only looked at the seaweeds found on rocky shores. The photographic index is organised by phyla with links to the families and then species. There is also an alphabetic list of scientific and common names with links to the individual species descriptions.


Seaweed Marine Algae