Kelp Forests

The laminarian kelps of the northern hemisphere occur at and below tide height, and are a large group of brown seaweeds that live on the seabed to depths at which sunlight penetration will allow - at around 10 to 20 metres.

Photo by Mike Deaton

These seaweeds are often seen growing in dense aggregations or 'forests' usually composed of a single species. The laminarians of which there are five species found at Lundy, typically have long strap like fronds with a short stubby stipe (stem) and are attached to the rocks by a structure called a holdfast. Each species had its own distinctive appearance and is distinguished by the type of location in which it grows' which is defined by depth and range of exposure to wave action.

Oarweed Laminaria digitata, Cuvie Laminaria hyperborea, Furbelows Saccorhiza polyschides, Dabberlocks Alaria esculenta and Sugar Kelp Laminaria saccharina are all kelp species which grow at Lundy. Forests of these kelp provide a rich and diverse living environment likened to that of a coral reef. The tree-like multi layered structure of the individual seaweed provides a wide variety of animals the ideal place to live or shelter. Small animals such as crustaceans, brittlestars, molluscs and worms live within the holdfast, while the fronds provide surface area for a range of colonial animals such as sea mats (bryozoans), and epiphytic seaweeds. In between the seaweeds animals such as sponges, urchin and other seaweeds colonise the rock surface and the large plants provide shelter to small or juvenile fish from predators. This combination of suitable structures allows for a diverse range of species to manifest itself as spectacular and thriving kelp community.

A second important function of kelp forests is the production of organic material. Kelps and the other seaweeds found in kelp forests grow by fixing carbon dioxide through the process of photosynthesis. The resulting vegetation eventually dies, producing flakes of rotting plant material and dissolved chemicals derived from plant material, both of which act as food sources for bacteria and single-celled animals. These, in turn, provide food for larger animals such as fish and lobsters.

At Lundy, kelp forests at Gannets bay and in Devil's Kitchen are protected by the sheltered bay' and beyond the Oarweed at low tide level are then dominated by kelp such as Laminaria hyperborea. On the more exposed west coast, it is Dabberlocks Alaria esculenta which dominates' as it is more tolerant of exposed sea conditions and wave action.