| Habitat factor |
Range of conditions |
| Salinity |
Full. Kelps are stenohaline in that they do not tolerate wide
fluctuations in salinity. |
| Wave exposure |
Extremely exposed, Very exposed, Exposed. Laminaria
hyperborea is unable to survive where wave action is extreme, since its stiff stipe,
topped with a large lamina, is prone to being snapped. In some areas, wave action
depresses the upper limit of the L. hyperborea habitat to several metres below MLWS
and under very severe wave conditions, the species may be absent. In such areas (e.g.
Rockall) Alaria esculenta will be found in the infralittoral zone owing to its
flexible stipe and thickened mid-rib which acts as reinforcement. |
| Tidal streams |
Very strong, Strong, Moderately strong, Weak, Very weak |
| Substratum |
Bedrock; stable boulders |
| Zone |
Sublittoral fringe; Infralittoral |
| Depth range |
0-50 m |
| 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 Saccorhiza
polyschides grows between 3oC-24oC (Norton 1970). Alaria
esculenta is tolerant of temperatures up to 16oC (Sundene 1962). Seasonal
adaptions 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 may have a strong influence on kelp
distribution and density within a kelp biotope. |
| Nutrients |
All kelp species are thought to be efficient absorbers of
nitrate and phosphate from seawater. However the quantities of these nutrients in seawater
vary 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). |
