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.
| Sensitivity to: |
Human activity |
Rank |
Comments |
| Siltation |
Waste: sewage discharge |
Intermediate |
Silt deposition may occur in the vicinity of sewage outfalls
and this can exert a number of detrimental influences on marine benthic algal communities
(Fletcher 1996). The sediment can cover all available substrata interfering with the
processes of spore attachment. They can smother young germlings and inhibit their growth
and development. Combined with water movement sediments can abrasively scour surfaces of
settled spores. |
| Changes in temperature |
Climate change/global warming |
Intermediate |
This would affect the biogeographical distribution of kelp
according to their temperature tolerances. |
| Changes in turbidity |
Extraction: navigational/ maintenance dredging |
Intermediate |
Dredging results in the suspension of the fine silt and clay
fractions of the sediment which is deposited by inshore currents. This will increase
turbidity and decrease the amount of penetrating light. |
| Hydrocarbon contamination |
Uses: boats/shipping (oil spills) |
Intermediate |
The mucilaginous slime covering kelps is thought to act as a
protective device (O’Brien & Dixon 1974). Laminaria digitata showed
reduced photosynthetic rates when emersed in crude oil (Schramm 1972). Laminaria
hyperborea however would never come into contact with freshly released crude oil as a
result of its continual emersion. |
| Changes in nutrient levels |
Waste: sewage discharge |
Intermediate |
The increase in levels of macronutrients in European coastal
waters results in the excessive growth of ephemeral macroalgal species. Increased
turbidity in coastal waters may also occur as a result of prolific phytoplankton growth. |
| Changes in oxygenation |
Aquaculture: fin-fish |
Intermediate |
Plumes of waste could stream over kelp forests leading to
anaerobiosis as a result of the oxygen demand of the decomposing material. Detrital rain
could also smother the surfaces of plants. Anti-microbial agents could be particularly
harmful to kelp biotopes because of the importance of bacteria in detrital cycling. |
| Removal of target species |
Collecting: kelp/wrack harvesting |
High |
Svendsen (1972) examined kelp beds over periods of up to 3
years after harvesting and found the Laminaria population to be dense after one year.
Although he regarded the beds as completely regenerated in terms of biomass only after 3-4
years. Sivertsen (1991) has compared the regrowth of kelp in areas trawled 1-5 years
previously with areas freshly trawled and control areas. Large canopy-forming plants were
absent until 4 years after harvesting, but the structure of the kelp population was
beginning to stabilize with little change in plant density from years 4-5. Harvesting may
also affect those species associated with the kelp biotope. Rinde et al., (1992)
studied the effects of kelp harvesting on other |
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common organisms within the kelp biotope and found |
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the forest structure to recover after 3-4 years. Persistent
differences from undisturbed forests were however found. |
| Removal of non-target species |
Collecting: shellfish (winkles, mussels) |
Intermediate |
The removal of predators such as lobsters and crayfish could
result in an unchecked urchin population, which could in turn destroy kelp populations in
the formation of ‘urchin barrens’. |
