Sensitivity to human activities

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


Although sheltered infralittoral kelp is tolerant of siltation, excessive siltation which occurs in the vicinity of sewage outfalls 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.
Changes 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.
Changes in turbidity Extraction: navigational/ maintenance dredging Intermediate Dredging results in the suspension of the fine silt and clay fractions of the sediment that is deposited by inshore currents. This will increase turbidity and decrease the amount of penetrating light.
Hydrocarbon contamination Uses: boats/shipping (oil spills)


The mucilaginous slime covering kelps is thought to act as a protective device (O’Brien & Dixon 1976). However, Laminaria hyperborea would probably 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. The localised increase in nutrient levels as a result of marine aquaculture could produce local eutrophication effects, particularly at slack tide.
Changes in oxygenation Aquaculture: fin-fish


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


Svendensen (1972) examined kelp beds over periods of up to 3 years after harvesting. He found the Laminaria population to be dense after one year but in terms of biomass considered the population to have completely regenerated after 3-4 years. Sivertsen (1991) has compared the re-growth 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. 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 argue that the forest does not provide the same physical environment for the other organisms that it shelters.

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