Substratum

The kelp species in the UK are most frequently found attached to submerged bedrock. However, given adequate water movement in the form of tidal currents rather than wave action, large kelp plants may frequently be found attached to cobbles and pebbles. When attached to small solid objects, the life-span of the plant becomes size- limited, since larger plants are more easily washed from their original location if only attached to a small stone. Kelps are found in almost all locations where some form of hard substratum is available within the euphotic zone in UK waters; see table below.

 Substrata colonised by kelp species in the UK

Kelp species

substrata

Alaria esculenta bedrock, stable boulders, cobbles, pebbles on large gravel, pontoons & moorings, man-made structures. Not in areas where there is sand scouring or siltation.
Laminaria digitata bedrock, stable boulders, pebbles on large gravel, stones on stable mud or sand, pontoons & moorings, other man-made structures. Not in areas subject to intense sand scouring but can be found in areas of siltation.
Laminaria hyperborea bedrock, stable boulders, pebbles on large gravel, deeper parts of pontoons and moorings, other man-made structures. Not in areas subject to sand scouring but can sometimes be found in areas of siltation.
Laminaria saccharina bedrock, stable boulders, pebbles on large gravel, stones on stable mud or sand, pontoons & moorings, other man-made structures. Not in areas subject to severe sand scouring but can be found in areas of siltation.
Saccorhiza polyschides bedrock, stable boulders, pebbles on large gravel, pontoons & moorings, other man-made structures. Not in areas subject to sand scouring but can be found in areas of siltation.
Undaria pinnatifida at present, mainly on man made structures, but may spread to bedrock, stable boulders

 

Where kelp species colonise unstable substrata, the populations are ephemeral. When the lamina reaches a certain area in relation to the mass of the item to which the plant is attached, the plant will be moved by the tide, wave action and current at the site. This frequently results in the plant being removed from the photic zone, either being cast ashore or deposited in deeper water, with the substratum exhibiting a dynamic fluctuation of colonisation and loss of kelp plants. On the shores of the NE Pacific, individuals of the annual kelp species Nereocystis luetkeana utilise the local water movement to migrate to deeper water as the plant increases in size (C. Hurd, pers.comm.).

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