Activities listed are those which influence, or are likely to influence this habitat
and which are assessed in the UK marine SAC project review. The sensitivity rank may
require amendment in the light of new information becoming available.
|Change in temperature
||Climate change/global warming
|This would affect the biogeographical distribution of kelp
according to their temperature tolerances. Unfortunately, global warming effects span
multiple generations of scientists and governments and the need for very long term
monitoring research has only recently been appreciated.
boats/shipping (oil spills)
|The mucilaginous slime covering kelps is thought to act as a
protective device (OBrien & Dixon 1976). Laminaria digitata showed
reduced photosynthetic rates when emersed in crude oil (Schramm 1972). Laminaria
hyperborea however would probably not come into contact with freshly released crude
oil because of its continual emersion.
|Removal of target species
||Collecting: kelp/wrack harvesting
|Svendensen (1972) examined kelp beds over periods of up to 3
years after harvesting and found the Laminaria population to be dense after one
year. He regarded the beds as completely regenerated in terms of biomass after 3-4 years.
Sivertsen (1991) compared the regrowth of kelp in areas trawled 1-5 years previously with
areas freshly trawled and also control areas. Large canopy-forming plants were absent
until 4 years after harvesting, but the structure of the kelp population was beginning to
stabilise with little change in plant density from years 4-5. A further interesting
observation was the replacement (for one year only) of the L. hyperborea-dominated
forest with a population of S. polyschides as in the clearance experiments by Kain
(1975). Harvesting may also affect those species associated with the kelp biotope. Rinde et
al. (1992) carried out a survey to establish the affects of kelp harvesting on common
organisms within the kelp biotope. They found the forest structure to recover to almost
normal after 3-4 years, but argued that the forest did not provide the same physical
environment for the other organisms which it shelters. The dredged areas tended to have
growth of other kelps on the bottom, e.g. Alaria esculenta, while the bottom
between the young L. hyperborea plants was uniformly covered with coralline algae
after 3 years. In the control areas there was a more diverse bottom community.
|Removal of non-target species
||Collecting: shellfish (winkles, mussels)
||The removal of predators such as lobsters and crayfish could
result in an unchecked urchin population, which could in turn destroy kelp populations and
form urchin barrens.