Habitat requirements
Habitat factor Range of conditions
Salinity

Full, Variable.

Wave exposure Sheltered, Very sheltered, Extremely sheltered
Tidal streams Moderately strong, Weak, Very weak
Substratum Bedrock, boulders, cobbles and mixed substrata
Zone Sublittoral fringe; Infralittoral
Depth range 0-20m
Temperature The kelp species of western Europe have relatively limited geographical ranges, which suggests that they are stenothermal and as such unable to tolerate large fluctuations in temperature. Laminaria hyperborea grows in a temperature range of 0oC – 15oC (Kain 1964), whereas L. saccharina has a slightly wider range of between 0oC-18oC. Seasonal adaptations to temperature tolerance do occur though increased temperatures during the winter months are less well tolerated than increased temperatures during the summer months (Luning 1990).
Water quality The light quantity and quality that is available to a kelp plant is dependent on the depth of water above the plant and its clarity. Absorption of light in coastal waters is influenced by the amount of particulate matter in suspension as well as by the dissolved oxygen components. Wavelengths of light are attenuated differentially as a result of these factors, altering the spectrum of wavelengths available at different depths. These effects probably have little influence on sheltered infralittoral kelp biotopes, as component species tend to be silt-tolerant.
Nutrients All kelp species are thought to be efficient absorbers of nitrate and phosphate from seawater. However the quantity of these nutrients in seawater varies throughout the year, with maximum levels being attained during the winter months. In spring when the nitrate concentration of the water is almost zero kelps continue to grow by means of their own internal reserves. However, after depletion of all reserves the growth rates decline in late spring and early summer, then external supply governs growth activity (Conolly & Drew 1985 a, b).

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