What is kelp and where is it found?
Kelps occur at and below low-tide level in cool temperate regions throughout the world. They are a group of large brown seaweeds that live on the rocky sea bed as far down as sunlight penetration will allow. The plants often grow together in large numbers to form dense forests, usually composed of a single kelp species.
There are two major groups of kelps. The laminarian kelps of the northern hemisphere, including British coastal waters, typically have strap-like blades and a relatively short stipe. In the South Atlantic, Pacific and Indian Oceans there is a second category of kelps – the ‘bladder kelps’ – which have greatly elongated flexible stipes bearing gas-filled bladders near the top. The bladders serve to buoy up the plants to help them make best use of surface sunlight. Both groups of kelps are attached to the sea bed by a structure called a holdfast. The holdfast has a superficial similarity to the root system of terrestrial plants; however, it does not penetrate the sea bed as the roots of land plants penetrate the soil, nor is it involved in the transfer of nutrients, which kelp plants derive directly from seawater.
The bladder kelps include the giant kelp, Macrocystis pyrifera, which is the largest marine plant known on earth. This plant, which forms dense beds off the coast of California, can grow up to 50m in length. Under optimal growing conditions, it can increase in length at a rate of 1m per day!
Laminarian kelp forests, composed mainly of cuvie, Laminaria hyperborea, are found on suitable rocky areas all around the Scottish coastline, reaching their greatest extent where the sea bed slopes gently away from the land. They are less common along the east coast, where much of the sea bed is composed of sand, and are particularly extensive around Skye and the adjacent mainland, along the west coast of the Outer Hebrides, and around Orkney and Shetland.